Progressive Crop Consultant - January/February 2020

January / February 2020 Tools, Tactics, and Strategies for Managing Postharvest Decay of Apple Fruit Management of White Rot of Onions and Garlic and Recent Research The Botrytis Gray Mold Fungus: Pervasive Pathogen, Formidable Foe Managing Diseases in a Rainy Year

PUBLICATION

Volume 5: Issue 1 January / February 2020

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PUBLISHER: Jason Scott Email: jason@jcsmarketinginc.com EDITOR: Kathy Coatney ASSOCIATE EDITOR: Cecilia Parsons Email: article@jcsmarketinginc.com PRODUCTION: design@jcsmarketinginc.com Phone: 559.352.4456 Fax: 559.472.3113 Web: www.progressivecrop.com

IN THIS ISSUE

4

Tools, Tactics, and Strategies for Managing Postharvest Decay of Apple Fruit

CONTRIBUTING WRITERS & INDUSTRY SUPPORT

12

Management of White Rot of Onions and Garlic and Recent Research

18

The Botrytis Gray Mold Fungus: Pervasive Pathogen, Formidable Foe

28

Biostimulants and Grape Production

32 36

Year-Round Mummy Management in Almonds

Joy Hollingsworth

4

UCCE Nutrient Management and Soil Quality Farm Advisor

Wayne M. Jurick II

Director. TriCal Diagnostics

Gabriel Torres

UCCE Tulare & Kings Counties

Lead Scientist and Research Plant Pathologist, USDAARS, Food Quality Laboratory, Beltsville, MD

Thomas Turini

Emily J. Symmes

Stephen Vasquez

PhD Sacramento Valley Area IPM Advisor UCCE and Statewide IPM Program

18

Steven T. Koike

University of California Ag and Natural Resources, Fresno County UCCE

Sun-Maid Growers Technical Viticulturalist

UC COOPERATIVE EXTENSION ADVISORY BOARD Kevin Day

Emily J. Symmes

County Director and

UCCE IPM Advisor,

UCCE Pomology Farm

Sacramento Valley

Advisor, Tulare/Kings County

Managing Diseases in a Rainy Year

Kris Tollerup Steven T. Koike

UCCE Integrated Pest

Director, TriCal Diagnostics

Management Advisor, Parlier, CA

32

The articles, research, industry updates, company profiles, and advertisements in this publication are the professional opinions of writers and advertisers. Progressive Crop Consultant does not assume any responsibility for the opinions given in the publication.

January / February 2020

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By WAYNE M. JURICK II | Lead Scientist and Research Plant Pathologist, USDA-ARS, Food Quality Laboratory, Beltsville, MD

Introduction: Apple Production, Storage and Rots

A

pples have an estimated annual farm gate value of nearly $4 billion dollars in the United States, with downstream revenues exceeding $15 billion (US Apple Association). Apples are stored for extended periods of time (up to six months at 1°C in air, and for one year maximum in controlled atmosphere) to preserve their quality and provide fruit yearlong to meet customer demands. During storage, fungal rots can cause significant amounts of decay resulting in product losses, reduced quality, and lower economic returns for producers. The three most problematic rot causing fungi in the United States are Botrytis cinerea (gray mold), Penicillium spp. (blue mold), and Colletotrichum spp. (bitter rot) (Figures 1A-C). Both gray mold and bitter rot occur in the field and during storage. However, Penicillium expansum and other Penicillium spp., are found exclusively in storage and are also economically important (Xiao and Boal, 2009). The focus of this article will be on the blue mold fungus,

but the information contained here is applicable to other fungal rot pathogens as well.

A

Figure 1

Blue Mold Biology

A survey of postharvest diseases in Washington State revealed that blue mold accounted for 28 percent of decay in storage (Kim and Xiao, 2008). Blue mold is characterized by a soft, watery rot that is light brown in color accompanied by the appearance of blue-green colored conidia on the fruit surface that develops at advanced stages of decay.

P. expansum and other Penicillium spp. do not directly infect fruits, as they require wounds often caused by stem punctures and severe bruises that occur before, during, and after harvest (Figure 1A). Blue mold spreads by spores that are produced terminally in chains on the surface of whorled conidiophores (Figures 2A and B, see page 6). Stem punctures, during harvest and handling, provide places for rot to occur, but the fungus can also enter natural openings like lenticels, open calyx/sinus, and

Continued on Page 6

B

C

Photo courtesy of Dr. Kari A. Peter, Penn State Fruit Research and Extension Center.

Figure 1: Top three most common postharvest diseases of apple in the United States. A. apples surrounded by a blue mold-infected fruit in a bin from commercial cold storage.

The disease is typified by blue-green colored conidia that form on the surface of soft-watery decay that is easily separated from the healthy portion of the fruit. B. Apple with gray mold symptoms typified by light gray colored mycelium and copious amounts of black hardened sclerotia on the surface of the fruit. C. Apple fruit in the field showing typical bitter rot symptoms caused by Colletotrichum spp. that also occur during storage. Note concentric rings of spores and spore-producing structures that are formed as the decayed area develops over time.

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January / February 2020

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Figure 2 B

A

Continued from Page 4 stem pull areas. Penicillium spp. also produce mycotoxins, such as patulin, citrinin, and penicillic acid, that pose potential human health risks when blue mold infected fruit are used to make juices and other processed products (Figures 3A-C). However, of the three mycotoxins, only patulin is regulated by the Food and Drug Administration (FDA) and European Food Safety Authority (EFSA) with a

Figure 2: Spore producing structures and conidia shown via scanning electron micrographs. A. Scanning electron microscopy (SEM) micrograph of conidia terminally produced in chains on a whorled conidiophore. B. SEM of conidia produced in chains which are typical dispersal units for Penicillium species.

maximal allowable limit of 50 parts per billion (50 µg/kg-1) and 10 µg/kg-1 for babies and young infant products (European Union (EU), 2006).

Decay Management 1. Postharvest fungicides Long term storage, coupled with lack of host resistance in commercial apple fruit cultivars, provides limited options but to rely on

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fungicides to manage postharvest decay of apple fruit (Rosenberger, 2012). Application of postharvest fungicides depends on the stage of product handling, and is typically made by bin drenching before storage, sorting line sprays, dips in flume water, together with fruit waxing, or by thermofogging storage rooms (Figures 4A-C, see page 9). There are four postharvest fungicides (Academy, Mertect,

Continued on Page 8

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Figure 3: Chemical structures of mycotoxins known to be produced by Penicillium species during apple fruit decay. A. patulin, B. citrinin, and C. penicillic acid. Of these three compounds, only patulin is regulated by the FDA and EU. Images courtesy of PubChem.

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Continued from Page 6 Penbotec, Scholar) registered and being used in the United States for apple fruits to manage postharvest decay. Both Scholar (active ingredient, fludioxonil) and Penbotec (active ingredient, pyrimethanil) were labeled for postharvest use in 2004 (Xiao and Boal, 2009).

Recent reports indicate reduced efficacy of these materials that

have resulted in increased blue and gray mold decay in commercially stored apple fruit in Pennsylvania and Washington State (Amiri et al., 2017, Yan et al., 2014; Gaskins et al., 2015). Thiabendazole (TBZ active ingredient, Mertect®), was labeled for blue mold management in 1968 and is applied primarily as a drench.

Consequently, repeated long term use of TBZ has resulted in resistant Penicillium spp. for multiple apple

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growing regions of the United States (e.g. New York, Pennsylvania, Maryland) and in British Columbia (Rosenberger et al., 1990; Sholberg and Haag, 1996; Jurick II personal observations). A new product (under the name Academy) was introduced in 2016, containing two single site mode of action fungicides, fludioxonil & difenoconazole, to manage postharvest decay on apples.

2. Sanitation Research studies have shown that fruit bins harbor fungal spores that serve as a source of inoculum to cause rot. Implementing physical (steam) or chemical (peroxyacetic acid, quaternary amines, etc.) sanitation methods in the packinghouse to reduce inoculum levels, reduces the incidence of fruit decay. While not commonly a stand-alone tool for postharvest rot management, bin sanitation complements existing chemical controls and helps to ensure their efficacy as resistant populations are kept in check (Rosenberger, 2012; Sholberg 2004; Hansen et al., 2010). Most inoculum of Penicillium spp. comes from the orchard soil and leaf litter as this pathogen can survive very effectively as a saprophyte (Lennox et al., 2003). Therefore, bins contaminated with soil and litter introduce this fungus into the packinghouse environment which is the source for the blue mold epidemic (Figure 5A-C, see page 10). Treating bins with steam, cleaning packinghouse walls and floors with quaternary amines or peroxyacetic acids, and maintaining proper chlorine levels in sizing flumes are all important measures that can have a positive impact in managing decay (Lennox et al., 2003). Hence, studies involving quantification of blue mold spores on bin surfaces in the Pacific Northwest region concluded that bin sanitation should be a component in an integrated decay management plan (Sanderson, 2000).

3. Fungicide resistance monitoring

A

B

Figure 4

C

Figure 4. Various methods for postharvest fungicide application. A. truck drench, B. bin drench, C. line spray wax.

Monitoring fungicide resistance in rot fungi is critical to maintain the efficacy of single-site mode of action fungicides. This is based on developing both, conventional and molecular-based methods, to detect fungicide-resistant pathogen populations. Routine monitoring can detect shifts in baseline sensitivity of pathogens and prevent postharvest fruit losses due to fungicide resistance. Site-specific or single site mode of action chemistries have been introduced that disrupt a metabolic process, and are more prone to develop resistance.

Baseline information is routinely derived from a representative pathogen population before an active ingredient is introduced to market (Russell 2004). This allows researchers to establish a Minimum Inhibitory Concentration (MIC) or discriminatory dose for a specific active ingredient generated from an “unexposed” pathogen population based on mean and the range of EC50 values. The EC50 is defined as the concentration of fungicide that reduces fungal growth by 50 percent compared to growth on non-amended media (Secor and Rivera, 2012).

Research by two collaborating groups in Washington State and Maryland have independently determined a mean EC50 for unexposed, difenoconazole-sensitive Penicillium spp. populations (Ali and Amiri, 2018; Jurick et al., 2018). Mean EC50 values for 130 P. expansum isolates

from Washington State was reported to be 0.17 ppm and was 0.16 ppm for 97 Penicillium spp. isolates largely obtained from Maryland and Pennsylvania. A discriminatory dose for monitoring difenoconazole resistance should be 1 ppm or higher and up to 5 ppm to detect truly resistant isolates. Baseline data, and corresponding discriminatory doses for MIC phenotyping, have been vital in monitoring fungicide resistance in Penicillium spp. populations and identifying fungicide-resistant blue and gray mold fungi (Li and Xiao 2008; Yan et al., 2014). Our laboratory has utilized published discriminatory doses for phenotyping fungicide resistant blue and gray mold pathogens with 0.5 ppm fludioxonil, 10.0 ppm Thiabendazole and 1.0 ppm pyrimethanil in agar-based Petri plates amended with technical grade chemicals (Li and Xiao 2008).

Recent Scientific Breakthroughs and Their Applications

The first genetic blueprint of the blue mold fungus was accomplished using Next Generation Sequencing Technology in the Penicillium expansum strain R19 (Yu et al., 2014). This isolate was obtained from decayed apple fruit in Pennsylvania commercial storage and shown to be highly aggressive when inoculated onto healthy apples. The P. expansum genome sequence is critical to understanding how this fungus develops resistance to various postharvest fungicides and has provided new clues about various infection strategies used by the

fungus to decay apple fruit. Using sophisticated computer software analysis programs, Yu et al. determined that P. expansum R19 has 62 different secondary metabolic gene clusters and toxin biosynthetic pathways including one for patulin production. Hence, the fungus can produce a wide variety of chemicals/toxins/small molecules that may provide new uses in medicine and biotechnology as most have yet to be characterized. By sequencing and comparing different Penicillium spp. strains, genes involved in apple fruit decay, toxin production, and sexual recombination have been discovered (Julca et al., 2016; Wu et al, 2018; Yu et al., 2014). Even though the blue mold fungus has the genetic capacity to undergo sex, a definitive sexual stage for this fungus has not been observed in the laboratory or in nature. The practical impact of this discovery is that the fungus has the potential for genetic recombination, which can allow for movement of genes controlling decay, toxin secretion and/or fungicide resistance between different strains of the blue mold fungus. Hence, recombination could result in more fit strains capable of resisting multiple modes of action chemicals, and or become more aggressive resulting in increased control failures during storage.

Translating fundamental scientific information on the blue mold fungus is important and is envisioned to gain deeper insights into the genetic toolbox used by Penicillium spp. to cause

January / February 2020

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B

A

Figure 5

C

Figure 5. Wooden commercial apple storage bins with A. copious leaf litter and B. visible fungal mycelium on the bin and fruit surfaces. C. blue mold fungi sporulating on the surface of a wooden storage bin. These photos emphasize the need to sanitize bin surfaces and remove infected fruit and leaves. Figure 4A and 5C courtesy of Dr Wojciech J. Janisiewicz—USDA-ARS Appalachian Fruit Research Station

Continued from Page 9 decay in apple fruit. Once elucidated, the fungal tools that it uses can be exploited to develop controls that block decay from developing on apple fruit during storage. This is a similar approach to what is being done in cancer research to discover new drug targets to fight tumorigenesis, block metastatic development, and aid in early detection. Uncovering the genetic mechanisms of fungicide resistance will help tailor specific classes of new chemicals and natural products that provide durable control with lower likelihood for developing resistance.

These discoveries will also enable the development of new detection tools that can be used not only by scientists, but producers as well, which would enable more timely detection of fungicide resistant isolates. Utilizing the latest molecular approaches such as CRISPR/ Cas9-mediated genome editing, RNA interference, and single gene deletion strategies can be integrated to attack the fungus at multiple points that are critical for it to cause decay. These new tools for decay management, detection of fungicide resistant strains, and next generation chemistries to control postharvest rot will be a welcomed addition to the producers’ management scheme resulting in less decay, maintaining fruit quality over an extended period, and providing safer apple products devoid of mycotoxins. These breakthroughs will have wide impact 10

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and benefit our stakeholders and customers in industry, the scientific community, and the public at large.

Conclusions & Summary

Postharvest decay management currently follows an integrated pest management strategy that focuses on the pathogen including sensible fungicide application, implementation of sanitation methods in the packinghouse, and periodic fungicide resistance monitoring efforts. Current knowledge concerning utilization of different postharvest chemistries based on FRAC codes (Fungicide Resistance Action Committee) suggests that rotation is critical to maintain product efficacy. However, more research must be conducted to determine the impact of chemistry type on selection of fungicide resistant rot isolates, the frequency of rotation (e.g. yearly vs. throughout the season) and impact of preharvest fungicides to predispose fungi in the field for developing resistance in storage. In the meantime, cold chain management, bin sanitation and proper fungicide use will help keep decay at acceptable levels until new controls and methods are developed, refined, and implemented. For more information on specific postharvest decay control measures, please check out online resources provided by Cornell University, Penn State, and Washington State University Extension

January / February 2020

programs via the world-wide web.

Acknowledgements

Dr. Wayne M. Jurick II is the research plant pathologist and lead scientist on the project entitled “Development of Novel Tools to Manage Fungal Plant Pathogens that Cause Postharvest Decay of Pome Fruit to Reduce Food Waste” which is funded by United States Department of Agriculture (USDA)-Agricultural Research Service (ARS) National Programs 303 Plant Diseases. Financial support was also made possible through multiple competitive grants awarded to WMJII from the State Horticultural Association of Pennsylvania.

References

Ali, E., Md. and Achour, A. 2018. Selection pressure pathways and mechanisms of resistance to the demethylation inhibitor-Difenoconazole in Penicillium expansum. Frontiers in Microbiology. doi: https://doi.org/10.3389/fmicb.2018.02472 Amiri, A., Mulvaney, K.A., and Pandit, L.K. 2017. First Report of Penicillium expansum Isolates With Low Levels of Resistance to Fludioxonil From Commercial Apple Packinghouses in Washington State. Plant Disease. 101:5.

Gaskins, V.L., Vico, I., Yu, J., and Jurick II, W.M. 2015.

First report of Penicillium expansum isolates with reduced sensitivity to fludioxonil from a commercial packinghouse in Pennsylvania. Plant Dis. 99:1182.

Hansen, J., Xiao, C.L., and Kupferman, G. (2010). Bin Sanitation: an effective was to reduce codling moth and fungal decay spores. WSU publication, 1-3

Jurick II, W.M., Macarisin, O., Gaskins, V.L., Janisiewicz, W.J., Peter, K.A., and Cox, K.D. 2018.

Baseline Sensitivity of Penicillium spp. to Difenoconazole. Plant Disease. 103:331-337.

Julca, I., Droby, S., Sela, N., Marcet-Houben, M., & Gabaldón, T. (2015). Contrasting genomic diversity in two closely related postharvest pathogens: Penicillium digitatum and Penicillium expansum.

Genome Biology and Evolution. 8: 218– 227.

Kim, Y.K., Xiao, C.L. 2008. Distribution and incidence of Sphaeropsis rot in apple in Washington State. Plant Disease. 92:940-946.

Lennox, C.L., Spotts, R.S., and Cervantes, L.A. (2003). Populations of Botrytis cinerea and Penicillium spp. on pear fruit, and in orchards and packinghouses, and their relationship to postharvest decay. Plant Disease 87, 639-644.

Rosenberger, D.A. 1990. Blue mold. In Compendium of Apple and Pear Diseases, A.L. Jones, and H.S. Aldwinkle, eds. (Saint Paul, Minnesota, APS Press), pp. 54-55.

Rosenberger, D.A. 2012. Sanitize apple storage rooms to minimize postharvest decays. Scaffolds Fruit J 21: 4-5.

expansum on apple fruit. Plant Disease 93:1003-1008.

Yan, H., Gaskins, V.L., Vico, I., Luo, Y., and Jurick II, W.M. 2014. First Report of Penicillium expansum isolates resistant to pyrimethanil from stored apple fruit in Pennsylvania. Plant Dis. 98:7.

Yan, H., Gaskins, V.L., Lou, Y., Kim, Y.K., and Jurick II, W.M. First Report of Pyrimethanil Resistance in Botrytis cinerea from Stored Apples in Pennsylvania. Plant Dis. 98:7. 2014.

Yu, J., Jurick II, W.M., Cao, H.Y., Yin, Y., Gaskins, V.L.,

Losada, L., Zafar, N., Kim, M., Bennett, J.W., and Nierman, W. (2014). Draft genome sequence of Penicillium expansum R19, which causes postharvest decay of apple fruit. Genome Announcements 2, e00635-00614

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Russell, P.E. 2004. Sensitivity baselines in fungicide resistance research and management. FRAC monograph. 3:1-54.

Sanderson, P.G. 2000. Management of decay around the world and at home. 16th annual Postharvest Conference, Yakima, Washington. Pages 1-8. http://postharvest .tfrec.wsu.edu/pgDisplay.php?article=PC2000Z. Secor, G. and Rivera, V. 2012. Fungicide resistance assays for fungal plant pathogens. In: Plant Fungal Pathogens Methods and Protocols (M.D. Bolton and B.P.H.J. Thomma, eds). New York: Springer, pp. 385-392.

Sholberg, P.L., and Haag, P.D. 1996. Incidence of postharvest pathogens of stored apples in British Columbia. Canadian Journal of Plant Pathology. 18: 81-85.

Sholberg, P.L. 2004. Bin and storage room sanitation.

Washington Tree Fruit Postharvest Conference.

Wu, G., Jurick II, W.M., Lichtner, F.J., Peng, H., Yin, G., Gaskins, V.L., Yin, y., Hua, S., Peter, K.A., Bennett, J.W. 2018.

Whole-genome comparisons of Penicillium spp. reveals secondary metabolic gene clusters and candidate genes associated with fungal aggressiveness during apple fruit decay. PeerJ. 1-17. 7:e6170. doi.org/10.7717/peerj.6170 Xiao, C.L., and Boal, R.J. 2009. Residual activity of fludioxonil and pyrimethanil against Penicillium

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11

Management of White Rot of

Onions and Garlic and Recent Research

By THOMAS TURINI | University of California Ag and Natural Resources, Fresno County UCCE

W

hite rot is caused by the fungus, Sclerotium cepivorum, which survives for decades in the soil as poppy seed-sized resting structures. If soil temperatures are between 50o and 75oF, compounds produced by onions and garlic trigger the fungus to break dormancy. Infection results in a soft rot of the garlic head or onion bulb, which will produce a white fluffy growth and then the poppy seed-like resting structures.

Very few resting structures (only two in about a pint of soil) can result in losses in these crops. Thousands of resting structures may be produced on each diseased plant. Therefore, the levels of this pathogen in the soil can increase very rapidly in fields with a susceptible crop, which is limited to onions, garlic and a few relatives. The resting structures are spread within a field with tillage equipment and are moved to other fields with anything that moves soil. It can also be moved into new areas on garlic planting material.

For many years, the primary approach to white rot

management was avoidance of infested fields. However, there are now more than 21,000 acres known to be infested with this pathogen and it is in areas where garlic and onions are important crops so it would limit production of these crops to completely avoid infested fields.

Sanitation Sanitation is an important approach to limit spread. Cleaning equipment between fields will not only reduce risk of movement of the white rot pathogen through a production area but also limit risk of other soilborne diseases. Planting white rot-free garlic planting material is critical in keeping the pathogen out of fields that are not infested.

Disease Management Several approaches to managing this disease hold promise.

Metam applications can reduce soil inoculum levels but soil preparation and moisture conditions are critical in optimizing Continued on Page 14

Thousands of the poppy seed-like resting structures of the fungus that causes white rot are produced on infected garlic heads. All photos courtesy of Tom Turini.

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January / February 2020

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Table 2. Influence of fungicide treatments at planting on d isease severity and yield of garlic, 2016-2017. z All fungicides were applied in the equivalent of 20 gal tank mix per acre concentrated in two 6-inch band over the planting trench before the placement of the garlic cloves, then the cloves are covered. y Foliar symptoms of white rot were rated on a scale of 0 to 10. Plots rated 0 were symptomless and plots rated 10 were completely collapsed. x Yield in tons per acre was calculated based on the hand harvested weight of 13 ft by a single 30 inch bed. w Means within a row appearing next to the same letter do not differ according to Least Significant Difference P=0.05.

Continued from Page 12

efficacy. Use of materials that emit compounds like those produced in the roots of onions and garlic to trigger germination of the resting structures in the absence of a host and starve out holds promise. However, additional work is needed to refine this approach for more reliable results than what has been observed experimentally.

Research efforts now are focused on quantification and increasing concentrations of active volatile compounds in onion and garlic containing materials, identifying the levels needed to trigger germination and the specifics of 14

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effective approaches in applying these materials in the field.

Some fungicides applied in the trench where the planting material is dropped has consistently reduced incidence and severity of white rot.

Fungicides applied through drip irrigation systems were not effective.

Three years of studies were conducted in which fungicides were applied through drip irrigation systems with tubing either on the surface shallowly buried or buried at six inches and the treated plots were always the same as the untreated control.

Commercial Field Evaluation During the 2016-17 and 2017-18

January / February 2020

production seasons, fungicides were evaluated in a commercial field naturally infested with white rot in Fresno County. Fungicides in three conventional categories were tested and in 2017-18, a non-living fermentation product with reported systemic acquired resistance activity was also included (Table 1, see page 13.) On 20 November 2016 and 11 November 2017, California late garlic was hand transplanted following the treatment of a 6-inch band of the trench into which the garlic cloves were dropped. The plots were rated on a scale from 0 to 10 with 0 being symptomless and Continued on Page 16

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“Herbicides are important in almond orchards,” says Pest Control Advisor/ “Alion does a really good job, “I continue to use Alion in a pre-emergent Certified Crop Advisor (PCA/CCA) has long residual weed control rotation because it’s a good product and David Vermeulen, Modesto, California. and it takes care of a lot of it works really well. We can see Alion “Weeds compete for nutrients. They broad-spectrum weeds…” reducing the weed population overall as compete for water. Those are probably soon as we start using it,” Garcia states. your bigger two issues in the almond “I think it’s one of the top – if not the top – pre-emergent product orchard, especially early on, so by keeping them down you have out in the market right now. Alion does a really good job, has long more water and more nutrients getting to the plant to get a better residual weed control and it takes care of a lot of broad-spectrum crop. Weeds also harbor insects – take morning glory, when you weeds that are giving us issues here in the Central Valley.” control it, you have a little less mite pressure in the orchard.”

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100 80

97.5

100

100

92.5

95

85 72.5

75

75

60 40 20 0

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Mission® at 2.15 oz./A + Roundup + Rely Fluvellin

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15

Tebuzol 3.6F 20.5 fl oz/a Velum One 6.75 fl oz/a

0.38

a

6.25

Cannonball WG 7 oz/A + SP2700 7.8oz/A

0.68

a

6.50

Fontelis 24 oz/a

0.88

a

5.52

A19649 13.7 fl oz/a

0.93

a

5.98

Rhyme 14 fl oz/a

1.00

a

5.99

A19649 8.55 fl oz/a

1.05

a

5.18

Cannonball WG 7 oz/A

1.63

ab

5.65

Untreated

2. 75

b

5.08

Table 3. Influence of fungicide treatments at planting on disease severity and yield of garlic, 2017-2018. z All fungicides were applied in the equivalent of 20 gal tank mix per acre concentrated in two 6-inch band over the planting trench before the placement of the garlic cloves, then the cloves are covered. y Foliar symptoms of white rot were rated on a scale of 0 to 10. Plots rated 0 were symptomless and plots rated 10 were completely collapsed. x Yield in tons per acre was calculated based on the hand harvested weight of 13 ft by a single 30 inch bed. w Means within a row appearing next to the same letter do not differ according to Least Significant Difference P=0.05. u Means within a column without letters to the right are not different at P=0.05.

Continued from Page 14

10 being collapsed. At maturity, 17 feet of each plot were hand dug and weighed, and per acre production was calculated. Data was subjected to Analysis of Variance and means were separated with Least Significant Difference P=0.05.

Under the conditions of these studies, most treatments had lower levels of above-ground symptoms than the untreated control. In the 2016-17 study, disease was severe and there were also significant differences in yields among treatments (Table 2, see page 14). The treatment with the highest 16

Progressive Crop Consultant

yield was 95 percent higher (more than four tons per acre) than the untreated control. Disease pressure was lower in 2017-18 and there were no yield differences among treatments (Table 3). Tebuzol, Fontelis, A19649 and Rhyme 14 fluid oz/a consistently had lower levels of disease than the untreated control. Cannonball with SP2700 and Velum One demonstrated efficacy in the season that these materials were included in the test.

Fungicides are not intended to be the only approach to management of this disease and are not likely to provide commercially acceptable levels of control as the soil inoculum levels

January / February 2020

continue to increase. In addition, risk of the pathogen becoming resistant to the fungicides increases with increased and repeated use. Fungicides in three different groups have now consistently demonstrated efficacy and trials are underway evaluating different approaches to management of this production issue.

The research mentioned in this article was supported by the California Garlic and Onion Research Advisory Board and by industry donors.

Comments about this article? We want to hear from you. Feel free to email us at article@jcsmarketinginc.com

Dry straw colored leaves and black appearance of the below-ground tissue of garlic characterizes infections occurring at early stages of crop development.

January / February 2020

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17

THE BOTRYTIS GRAY MOLD FUNGUS:

PERVASIVE PATHOGEN, FORMIDABLE FOE

By STEVE KOIKE | Director, TriCal Diagnostics

Photo 1

Photo 2

On lettuce, Botrytis results in a crown rot and gray carpet of spores that causes total plant collapse.

All photos courtesy of Steve Koike.

Greenhouse grown tomatoes can develop Botrytis-caused cankers that kill entire stems.

Strawberry fruit are very susceptible to gray mold caused by Botrytis.

Photo 3

Photo 4

Introduction and Significance

W

hen evaluating the impact and importance of a plant pathogen, one could consult various metrics to make such an assessment. One could consider the values of the affected crops, the acreages planted, the geographic distribution (how widespread is it?) of the pathogen, the mode of pathogen attack (does it affect leaves, flowers, both?), the persistence and staying-power of the organism, and the difficulty in controlling the patho18

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Ornamental crops such as poinsettia can develop leaf, stem, and flower diseases caused by Botrytis.

gen. The Botrytis fungus, causal agent of gray mold and other related diseases, is one of the few plant pathogens that could arguably be placed at or near the top of a key pathogen list based on all of these criteria. Field professionals likely are familiar with the challenges of gray mold for the crops they oversee. However, what may be overlooked is the impact of Botrytis throughout a broad spectrum of many agricultural commodities and settings. Botrytis is an unusually dangerous threat due to its ability to infect dozens of crops, un-

January / February 2020

common versatility as a microorganism, and propensity to change genetically in adapting to fungicide chemistry.

Broad Spectrum Impact on Crops Worldwide

Botrytis is a highly ranked plant pathogen due to its broad host range that includes hundreds of plants. Such hosts are in almost all commodity groups: annuals and perennials, herbaceous and woody plants, food

Continued on Page 20

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Vegetative

Flower

Fruit

Alfalfa

Crown and stem rots

...

...

Almond

...

...

Jacket rot on green fruit

Apricot

...

...

Jacket rot on green fruit

Artichoke

...

Flower bud bract rot

...

Bean

...

...

Pod rot

Caneberry

...

...

Ripe fruit rot

Cherry

...

Blossom blight

...

Citrus

Twig Blight

Blossom blight

Fruit rot

Cucurbits

...

...

Fruit rots

Grape

Shoot Blight

...

Bunch rot

Hemp/Cannabis

Foliar Blight

Bud blight

...

Lettuce

Transplant collapse, crown rot

...

...

Onion*

Leaf blight, neck rot

...

...

Ornamentals

Foliar and shoot blights

Petal spots, flower blights

...

Pea

...

...

Pod rot

Peach

...

...

Jacket rot on green fruit

Pepper

Stem grinding

...

Green and ripe fruit rots

Strawberry

...

Flower blight

Fruit rot

Tomato

Foliar blight, stem girdling

...

Green and ripe fruit rots

Table 1. Examples of Vegetative, Flower, and Fruit diseases caused by Botrytis on diverse crops. *In contrast to most other crops, Botrytis diseases on onion are not primarily caused

by Botrytis cinerea but by other Botrytis species.

Continued from Page 18 and ornamental crops, vegetable and fruit and field crops. Included within this diverse list are dozens of high value vegetable, fruit, and ornamental commodities (examples are listed in Table 1 and seen in Photos 1 to 4, see page 18), for which gray mold can inflict sizeable economic losses.

This broad spectrum of activity can also be described based on the type of plant tissue affected. Depending on the crop host, Botrytis can infect the vegetative portions (stems, petioles, leaves), flowering parts (buds, sepals, 20

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petals, reproductive tissues), and fruit (immature and ripe phases).

The Botrytis impact on all these crops and commodity groups is further compounded by two factors. First, the gray mold fungus can cause significant disease both before and after harvest.

Pre-harvest disease occurs when Botrytis is active on developing plants in the field and greenhouse, resulting in blight, decay, and rot that reduces crop quality and harvestability. In addition, for many crops the Botrytis fungus can be a contaminant on or even inside

January / February 2020

the harvested plant commodity. Once these contaminated commodities are stored, the Botrytis fungus can become activated under certain postharvest conditions and cause rots and decay in storage (Photo 5, see page 21).

Secondly, we note that Botrytis is found throughout most agricultural and horticultural production regions in the world. In the USA, there are only a few states where an official report of Botrytis is lacking. Likewise, Botrytis is found throughout the world and is reported to cause disease on a huge number of crops and plants.

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21

Versatility as a Microorganism

A notable feature about Botrytis is the organism’s ability to function in different modes or survival strategies.

This diversity of biological activity is not commonly seen in plant pathogens and points to the extreme versatility of Botrytis as a microorganism.

Pathogen: We are most aware of Botrytis as an aggressive, difficult to control primary pathogen of plants.

From an agricultural point of view, this is the most prominent role for Botrytis. Saprophyte: In a different mode, Botrytis does not even need a living plant. As a saprophyte, the gray mold fungus can grow, thrive, and reproduce on senescent, dying, and dead organic plant tissue. Spores that land on decaying matter can readily germinate and colonize such substrates.

Secondary invader: If a plant is injured from weather extremes, damaged from mishaps in the field, or has symptoms caused by other pathogens, spores of Botrytis can drop onto such compromised plant tissues and aggressively grow on and overwhelm the injured plant. In such situations Botrytis did not initially cause the problem but is a secondary invader that can make the overall problem worse.

Dormant sleeper: Botrytis can be a sneaky adversary. This pathogen can infect and penetrate plant tissues but remain dormant within the protection of its host. Later, when the conditions change, the weather warms, or the plant tissues mature and grow, the once dormant Botrytis wakes up and begins to colonize the host, resulting in gray mold disease. Such dormant infections are called latent or “quiescent” infections. Opportunist: Botrytis is an opportunist because it can switch from being a harmless saprophyte, growing on dead tissue that growers do not care about, to an aggressive pathogen causing problems. Numerous examples exist of this switching. The Botrytis starts by colonizing dead parts of plants, such as old flower parts; if these Botrytis-laden dead pieces are in contact with healthy tissue, the Botrytis is able to bridge over from the dead 22

Progressive Crop Consultant

Photo 5: On pea, Botrytis can cause a pre-harvest disease but is perhaps more important as a postharvest problem, as seen by these lesions on stored pea pods.

to the living, resulting in a primary disease problem (Photo 6, see page 24).

Gray mold is also versatile in how it survives and is moved around in the agricultural environment. Airborne spores: The gray color of the fungus, as it appears on infected plants, indicates Botrytis is producing millions of spores.

contaminant. Embedded mycelium: In another survival mode, the hyphal strands of Botrytis can penetrate and be buried inside the living flowers, buds, or stems of plant hosts. This strategy allows the gray mold fungus to be protected from harsh environmental conditions, giving it an opportunity to wait for more favorable situations.

A notable feature about Botrytis is the organism’s ability to function in different modes or survival strategies.

These spore masses (Photo 7, see page 26) are readily spread long distances by winds, splashing water, and physical contact. Sclerotia: Under certain conditions Botrytis can produce a survival structure, the sclerotium, which is a hard, black, oblong to spherical structure that can be up to ½ inch long.

Sclerotia can withstand dry, warm, or cold conditions and can survive inside dead crop debris or buried in the soil; under conducive conditions these sclerotia can germinate and produce mycelium that infects the host. Sclerotia can form within the hollow stems of plant hosts and be carried with the plant if these stems are moved to other locations. Sclerotia can become mixed in with seed and become a seedborne

January / February 2020

Genetic Plasticity and Loss of Fungicide Efficacy

Botrytis is notorious for becoming resistant (insensitive) to fungicides because of its high genetic variability and adaptability, profuse production of spores, and multiple cycles of spore production. Molecular recombination, mixing of genes between strains, and mutations provide the raw genetic material for resistance to develop.

When fungicides are applied numerous times to a susceptible crop, the presence of the chemical challenges Botrytis can result in the selection of individual strains that are no longer affected by that chemistry. Fungicides with single-site modes of action are

Continued on Page 24

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Continued from Page 22 especially at risk for inducing resistance in Botrytis. Worldwide, resistant isolates of Botrytis have been confirmed for all of the single-site fungicide categories used to manage gray mold (Table 2, see page 22). Even more alarming are the research findings that show individual isolates of Botrytis can possess resistance to multiple fungicide classes; there are even isolates that are shown to be resistant to seven different fungicides, each of which has a different mode of action.

Site-specific Fungicide Classes for Botrytis

FRAC* no.

Anilinopyrimidine

9

Dicarboxamide

2

Hydroxyanilide

17

Methyl benzimidazole carbamate

1

Phenylpyrrole

12

Polyoxin

19

Quinone outside inhibitor

11

Succinate dehydrogenase inhibitor

7

A Note About Botrytis Species

This article is addressing the broad topic of gray mold caused by Botrytis, and for most crops the pathogen species is Botrytis cinerea. However, examining the DNA of Botrytis from different crops in different parts of the world, powerful molecular tools and innovative techniques are detecting multiple, diverse genetic signatures which indicate that B. cinerea is not the only gray mold species out there. For example, a series of studies documents that strawberry can be infected by one or more of the following Botrytis species: B. cinerea, B. fragariae, B. caroliniana, B. mali, B. pseudocinerea.

Such findings can have implications for the farmer and the field. On grapes in France, for example, the B. pseudocinerea species is more active in the early spring, while B. cinerea is active in both spring and fall. There are indications that a higher percentage of B. pseudocinerea isolates are resistant to some fungicides than B. cinerea isolates. So in the future it might be critical to know exactly which species is causing gray mold, since different species may require slightly different management approaches.

Table 2. Fungicide classes for use against Botrytis and for which resistance has been reported. * FRAC = Fungicide Resistance Action Committee

Management of Gray Mold

Controlling gray mold diseases requires the implementation of IPM practices. Fungicides: Judicious and strategic use of fungicides remains

Continued on Page 26

24

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Photo 6: Botrytis can cause a brown decay on orange fruit by first colonizing dead flower parts that stick to the fruit; here the old blossom has been moved aside to show the developing brown lesion.

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Photo 7: Botrytis produces masses of airborne spores that readily land on host crops.

Continued from Page 24 the primary means of managing gray mold. Multiple applications usually are needed, throughout the season, using diverse products having different modes of action. Fungicides with single-site modes of action are especially at risk for inducing resistance in Botrytis, so multi-site products should be integrated into spray programs. Sanitation: Sanitation measures, such as the removal of dead leaves and diseased fruit, appear to only slightly decrease gray mold incidence and cannot replace reliance on fungicide programs. Given the logistical difficulty and expense of such measures, these sanitation steps are not practical for most commercial

growers but could be a consideration in certain circumstances, such as for greenhouse crop production.

Modifying the environment: Because Botrytis is dependent on free moisture and high humidity, reducing such factors can help reduce disease severity.

The venting out of moist air in a greenhouse is one example of such environmental modifications. Use of drip irrigation is a field equivalent of reducing water on foliage and can reduce gray mold severity. Canopy modification (pruning to remove leaves and laterals and increase air flow and light penetration) can help with bunch rot control in grapes. Resistant or tolerant cultivars: For most crops there are no cultivars that are genetically resistant to Botrytis.

Because Botrytis is dependent on free moisture and high humidity, reducing such factors can help reduce disease severity.

26

Progressive Crop Consultant

January / February 2020

However, some cultivars may experience less gray mold for other reasons.

For example, some strawberry cultivars suffer less gray mold due to the upright growth habit of leaves and flowers. Use such cultivars if available. Reduce damage: Reducing damage to crops in the field will reduce the opportunities for Botrytis to invade as a secondary decay organism. Proper harvesting and postharvest handling of fruit are critical to reducing fruit injury and lowering the impact from gray mold.

Storing fruit at low temperatures is also necessary to retard gray mold and slow down the aging and senescing of fruit.

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27

Biostimulants and Grape Production

By JOY HOLLINGSWORTH | UCCE Nutrient Management and Soil Quality Farm Advisor and STEPHEN VASQUEZ | Sun-Maid Growers Technical Viticulturalist

B

iostimulants are a broad category of biological products used in crop production to enhance and/or improve conventional nutrition programs. The term “biostimulant” was officially defined in the Agricultural Improvement Act (aka Farm Bill) of 2018 as:

“[Plant biostimulants are] a substance or micro-organism that, when applied to seeds, plants, or the rhizosphere, stimulates natural processes to enhance or benefit nutrient uptake, nutrient efficiency, tolerance to abiotic stress, or crop quality and yield.”

However, on March 25, 2019, the US Environmental Protection Agency (EPA) released a report titled, “Draft Guidance for Plant Regulator Label Claims, Including Plant Biostimulants” to better understand manufacture label claims for plant growth regulators and biostimulants. In it, the EPA defined biostimulants in much the same way as found in the Farm Bill, except that EPA’s definition refers to improving soil as a possible outcome rather than crop quality or yield.

The EPA is deciding if and how biostimulants should be regulated. If manufacturers make claims that are similar to plant growth regulators, which are subject to regulations found in the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), then they would require registration with the EPA. Some see this as an opportunity to raise the bar on biostimulant products, and reduce outrageous claims not 28

Progressive Crop Consultant

January / February 2020

supported by replicated field research.

Others are less optimistic about more regulation and the potential for increased costs on useful products or the complete loss of product categories.

Biostimulant Categories

Biostimulants fall into three general categories 1) acids (such as fulvic or humic), 2) microbials (such as beneficial fungi or rhizobium), and 3) extracts or secondary metabolites (such as polyphenols or botanicals). However, there are other types of products, such as nitrogenous compounds or proteins, which don’t fit neatly into the primary categories (Heacox 2018). Acid based products can be applied as foliars, through irrigation systems, or directly to the soil. Depending on application, they have been shown to reduce plant stress, increase root growth and/or improve soil health. Microbial products are primarily fungi or bacteria that help improve nutrient uptake either directly or by improving soil conditions for the plant. Some microbial products may need an incubation period prior to use, which requires planning if large acres will be covered. Extracts can also be applied as foliars or through irrigation systems. They have been found to improve soil conditions for roots or microbes that are able to make elements more available.

Biostimulants vs Fertilizers

It is important to remember that biostimulants are not fertilizers.

Inorganic fertilizers are mineral salts that consist of single or multi-nutrient constituents in varying ratios (i.e. calcium ammonium nitrate=CAN17).

In contrast, organic fertilizers are plant and/or animal derived products that also have varying ratios of elements. Both types of fertilizers are regulated with a focus on quality and quantity guaranteed by manufactures.

Biostimulants are biological products that improve crop growth through a variety of methods (i.e. reduce plant stress, improve nutrient uptake). They may have some low levels of nutrient value, but that is not their primary benefit to crops. Biostimulant activity is not fully understood but it is thought that they act indirectly to improve crop health by increasing soil microbe activity, or through the additions of acids, plant hormones, or metabolites that react with the biological processes.

Biostimulant research is ongoing and has increased substantially since 2010 to help demonstrate their impact and activity on plant growth. Dr. Russell Sharp of Plater Bio, who spoke with AgriBusiness Global, said that in 2010 a combination of new technologies, increasing interest from investors, and lower growth in traditional pesticide and fertilizer sales, led to a greater interest in biostimulants (Pucci 2018).

Given the number and diversity of biostimulants, performance claims about what can be achieved when applied to a crop vary widely. Some evidence suggests biostimulants may reduce plant stress by improving soil environmental conditions when there is a water deficit, high disease pressure, non-optimal pH, or salinity levels in the soil that might otherwise reduce plant health or growth. Under these conditions, biostimulants are thought to increase nutrient uptake and yield, and may even improve fruit quality.

Some research has found microbial products solubilize essential nutrients to increase their availability to the crop and enhance drought tolerance by stimulating root growth (Calvo et al.

2014). Still, while some work has shown that adding microbes to the soil benefits crops, other research shows less positive results. One study found establishment of arbuscular mycorrhizal fungal inoculants was highly variable at

best and did not significantly improve crop growth even when they were present (Hilton 2019). Limited conclusive data suggests growers should view biostimulants as products that enhance the efficiency of fertilizers so that less is required during the season.

Considerable research has focused on biostimulant use in annual crops, but less research exists for permanent crops such as grapes. Biostimulant grape research has mostly been with foliar applications. Foliar applications pose the benefit of entering the plant and potentially reacting more rapidly with the biological processes than if they were applied to the soil. Foliar applied biostimulants that have shown benefits to grapes include chitosan, which improved postharvest grey mold infections equally as well as synthetic fungicide applications (Romanazzi et

al. 2006). Chitosan was also shown to protect against downy mildew (Romanazzi et al. 2016), which is a devastating disease that impacts foliage and fruit. Some studies have shown improved anthocyanin concentrations, which are an important component of grape and wine color. Foliar seaweed applications increased levels of anthocyanins and phenolics (Frioni et al.

2018), both important characteristics of wine. Another study showed that methyl jasmonate and yeast increased anthocyanins in Tempranillo grapes and wine when applied foliarly (Portu et al. 2016). Methyl jasmonate is a plant growth regulator and an elicitor, a type of organic biostimulant that can induce the synthesis of phenolic compounds, which then triggers defense reactions (Gutierrez

Continued on Page 30

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29

Continued from Page 29 et al. 2019). Methyl jasmonate is one of the most effective elicitors, but its use can be cost prohibitive.

Although biostimulants have been available for some time, and researched since the mid-seventies, more research is needed before conclusions are drawn on perennial crops. The multitude of products manufactured under the biostimulant umbrella, and their unique impacts on the numerous US perennial crops grown in different climates, necessitates multiple years of research to better understand their benefits.

On-Farm Research Trials

Growers interested in biostimulant products are encouraged to test them in their own vineyards. They should work closely with a Certified Crop Advisor (CCA), Pest Control Advisor (PCA) or university extension advisor to identify what plant health problem needs to be solved (i.e. improved nutrient uptake). On-farm trials should be designed so they can be repeated over multiple years and help determine if they improve production and solve the problem of interest. When possible, a trial site that reduces variables that may impact results should be chosen.

For example, if improved nutrient assimilation is the goal, a trial site that has a consistent soil type would produce the best results by eliminating soil as a variable. Clay verses sandy soils retain nutrients differently and will impact plant nutrient and water uptake. Select products that claim to solve or improve a problem that has been experienced at a location over several years. Do not attempt to evaluate too many different products at once since it will make trial results more difficult to interpret. A “grower standard” is important to include so comparisons can be made against the experimental biostimulant regime.

Collect data on the plant characteristics that you expect to see a change. For example, if the products being tested claim to improve yield or fruit quality, take fruit samples from each test block and compare them. If product 30

Progressive Crop Consultant

claims are to improve plant nutrient absorption, collect leaves and/or petioles and have them analyzed by a commercial analytical lab. However, when collecting samples for data analysis, it’s important to be aware of edge or perimeter effects. Plants near edges of a plot tend to grow differently than plants in the middle of blocks that have competition for water or sunlight, and this can confound results.

When possible, implement a replicated on-farm trial so that you have multiple locations to review treatments. If results from a replicated trial are consistent, that is a good indication that the biostimulants are the cause.

G, Garde-Cerdán T, Pérez-Álvarez EP. 2019. A review of the use of biostimulants in the vineyard for improved grape and wine quality: effects on prevention of grapevine diseases. J Sci Food Agric. 99(3):10019. https://doi.org/10.1002/jsfa.9353

Contact a local CCA, PCA or university extension advisor to help design the trial, decide what data needs to be collected and interpret the results so the best information is gathered from an on-farm research trial.

Portu J, López R, Baroja E, et al.

2016. Improvement of grape and wine phenolic content by foliar application to grapevine of three different elicitors: methyl jasmonate, chitosan, and yeast extract. Food Chem. 201:213-221. https://doi. org/10.1016/j.foodchem.2016.01.086

More Information

To learn more about the use of biostimulants you can visit the Biological Products Industry Alliance (BPIA) website: https://www.bpia. org/ BPIA is an organization with membership from manufactures of various biostimulant products. Their focus is “advancing sustainability through biological solutions”, working with regulators to improve product registration and distribution and to educate producers on products and their best use for different crop production systems.

References

Calvo P, Nelson L, Kloepper JW. 2014. Agricultural uses of plant biostimulants. Plant Soil 383(1-2):3-41. https://doi. org/10.1007/s11104-014-2131-8 Frioni T, Sabbatini P, Tombesi S, et al.

2018. Effects of a biostimulant derived from the brown seaweed Ascophyllum nodosum on ripening dynamics and fruit quality of grapevines. Scientia Horticulturae. 232:97-106. https:// doi.org/10.1016/j.scienta.2017.12.054 Gutiérrez-Gamboa G, Romanazzi

January / February 2020

Heacox L. 2018. Biostimulants gaining ground. CropLife. https://www.croplife. com/special-reports/biologicals/ biostimulants-gaining-ground/ Hilton S. 2019. Are biofertlizers actually effective? Team-Trade. https://blog.teamtrade.cz/ are-biofertilizers-actually-effective/

Pucci J. 2018. What’s really behind the biostimulant boom. AgriBusiness Global. https://www.croplife.com/crop-inputs/ micronutrients/whats-really-behind-the-biostimulant-boom/ Romanazzi G, Nigro F, Ippolito A, et al. 2006. Effects of pre and postharvest chitosan treatments to control storage grey mold of table grapes. J. Food Sci. 67: 1862-1867. https://doi. org/10.1111/j.1365-2621.2002.tb08737.x Romanazzi G, Mancini V, Feliziani E, et al. 2016. Impact of alternative fungicides on grape downy mildew control and vine growth and development. Plant Dis. 100(4):739-748. https:// doi.org/10.1094/PDIS-05-15-0564-RE

Comments about this article? We want to hear from you. Feel free to email us at article@jcsmarketinginc.com

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31

Year-Round Mummy Management in Almonds

Photo 1. Almond mummies.

Photo by Jack Kelly Clark, courtesy UC Statewide IPM Program

By EMILY J. SYMMES| PhD, Sacramento Valley Area IPM Advisor UCCE and Statewide IPM Program

A

s we all know, the key to effective navel orangeworm (NOW) management in nut crops is sanitation. Mummies provide the only bridge within the orchard environment for NOW from one cropping season to the next. As we also know, thorough sanitation on every acre of almonds, walnuts, and pistachios in the state is challenging, perhaps increasingly so due to logistical, environmental, and

economic factors. With rising labor costs, reduced labor availability, less fog events in the valley, and orchard access issues due to excessive rainfall some years, it is easy to see why sanitation efforts are not being accomplished as thoroughly as we all would like. There is also plenty of evidence to support that incorporating a multitude of additional crop protection tactics in-season (i.e., more numerous pesticide applications,

addition of mating disruption or mass trapping) cannot replace a robust sanitation program for NOW damage reduction.

Of course, we think about mummies for a good part of every year, typically focused on them between harvest one year and hullsplit the following

Continued on Page 34

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“We always like to recommend that our fungicides are used in a preventive manner prior to there being disease issues. So proper timing is very important,” says Matthew Wilson, field sales representative for Bayer.

Scala fungicide is notable for its control of Brown rot blossom blight at pink bud as an early-season spray option. It also offers both preventive and curative activity, rapid penetration and an ease of mobility into the bud and blossom. It is crop safe, mixes well with IPM programs and other products, and is effective across a wide range of temperatures and weather conditions, with minimal adverse effects on beneficial insect species.

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Luna Experience and Luna Sensation are strong choices for maximizing yields by providing longlasting, broad-spectrum disease protection when applied at bloom. Luna penetrates green tissue and moves systemically into closed buds, protecting against Brown rot blossom blight, Jacket rot, Shot hole, Anthracnose, Scab, Rust and Alternaria. It also offers two built-in modes of action for each product, providing the flexibility to alternate FRAC groups for more effective fungicide resistance management.

“I use Luna products predominantly in the bloom time for a myriad of diseases,” says PCA David Vermeulen of Vernalis, California. “I like the ease of handling, and it mixes well with a number of other products. It also covers a broad spectrum of different fungal diseases I’m going after.”

Diseases to Watch /// Brown Rot Blossom Blight – Thrives in humid temperatures with or without rain. /// Anthracnose – Originates in warm, rainy weather. /// Jacket Rot – Rare, but, under cool and wet conditions at bloom, can cause devastating loss. /// Scab – Favors wet weather and spreads to new sites by wind or rain. /// Shot Hole – Requires prolonged periods of moisture, and water moves spores to new sites.

PCA Ryan Garcia of Salida Ag Chem in Modesto, California, uses Scala. “I’ll use it in the early stages of bloom for Brown rot blossom blight. I think it’s a great material.”

/// Alternaria – Develops with high humidity where dew forms and air is stagnant. /// Rust – Favors humid conditions, worsens in rainy weather and spreads easily by wind.

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Contact your Bayer representative or visit LunaScalaGamePlan.com. © 2019 Bayer Group. Always read and follow label instructions. Bayer, the Bayer Cross, Luna, Luna Experience, Luna Sensation, and Scala are registered trademarks of the Bayer Group. Not all products are registered for use in all states. For additional product information, call toll-free 1-866-99-BAYER (1-866-992-2937) or visit our website January / February 2020 www.progressivecrop.com at www.CropScience.Bayer.us. Bayer CropScience LP, 800 North Lindbergh Boulevard, St. Louis, MO 63167.

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33

Continued from Page 32 year, when the new crop becomes susceptible to NOW infestation. We primarily focus on these mummies as a bridge for overwintering NOW and the sole resource for early generation development, and rightfully so.

However, we also need to consider the multitude of orchard factors that cause mummies in the first place. If we can effectively reduce the overall mummy load after harvest, then we can save inputs (labor, money) required to remove those mummies through sanitation efforts. It is also worth noting that mummies remaining in trees throughout the subsequent growing season (even those not contributing to NOW build-up) can get shaken and incorporated into the current season harvest, and contribute to off-grade quality/reject totals.

A number of season-long factors can contribute to mummy load in an orchard, including sticktights caused

by disease, arthropod injury, nutrient and irrigation issues, overall tree health, uneven ripening, and other issues that result in poor crop removal at harvest. Taking a holistic, yearround approach to managing all of these elements (at least those we can control) will have a positive impact on reducing NOW damage the following season, and help growers achieve their sanitation goals more economically.

Irrigation and Nutrient Management

Irrigation and nutrients (too much or too little) can affect crop removal and ultimate mummy load through influence on disease development (i.e., hull rot), orchard vigor, onset/ duration of hullsplit, uneven ripening, and ultimate incidence of sticktights.

Excessively vigorous orchards (driven by irrigation and/or nitrogen inputs) can exhibit delayed ripening. Using a pressure chamber to monitor midday stem water potential is the gold standard for scheduling irrigation and

Photo 2. Navel orangeworm in almond mummy.

Photo courtesy of Emily J. Symmes.

guiding regulated deficit irrigation approaches in almonds. Careful nitrogen management applied at the appropriate rates and times can regulate orchard vigor and improve crop removal, as well as decrease the incidence of hull rot. The Almond Doctor Blog and Sacramento Valley Orchard Source websites both contain numerous informative articles on the use of pressure chambers in nut crops, as well as nitrogen management guidelines. Boron toxicity can also cause gumming and sticktights.

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Photo 3. Almond mummy with new crop nuts.

Photo by Jack Kelly Clark, courtesy UC Statewide IPM Program

Photo 4. Hull rot in almonds.

Photo by Jack Kelly Clark, courtesy UC Statewide IPM Program

from hull samples at harvest (leaf sample values are not effective).

Uneven ripening and difficult nut removal can result in shaker damage.

Trees with prior shaker damage are more prone to stress and disease which can lead to faster hull-split advancement, and increased sticktights at harvest. These trees use less water and are therefore often over-irrigated, which can cause increased hull rot incidence, leading to poor nut removal as well as further shaker damage risk.

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Insect feeding (leaffooted bugs, stink bugs, and other Hemipterans) at certain times of the year can cause hull gummosis that can lead to sticktights if nuts are not aborted as a result of the injury. Similarly, certain diseases that cause gummosis of the hull or peduncle attachment (e.g., anthracnose, hull rot) will likely become mummies after harvest.

Effective mummy management can also reduce the prevalence of inoculum sources for pathogens that overwinter on mummies, such as brown rot, bacterial spot, and anthracnose.

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January / February 2020

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35

Managing Diseases

in a Rainy Year

By GABRIEL TORRES | UCCE Tulare & Kings Counties

T

he climate in California is described as Mediterranean. This means that our summers are dry and hot, while winters are mild and wet.

However, the weather in 2019 did not behave as expected. With cool temperatures in February, a drier than normal April, and an unusually cool and rainy May 2019 will be remembered as an extraordinary weather year. It is impossible to say if this would be the new normal, but it is clear, that something happened in our local weather during 2019.

By October 1st, 2019, information collected from different CIMIS stations in the San Joaquin Valley (SJV) demonstrated that the average high monthly temperature was lower by 6 F° for February and May (Table 1, see page 38 and Figure 1, see page 39). This phenomenon pushed the average high temperatures in February below 60 F° delaying bud break up to two weeks. In May, the average high temperatures were below 80 F°, favoring disease outbreaks.

Precipitation Data

For precipitation, the data collected from CIMIS indicates annual rainfall was highly variable between locations.

Some stations received 30 percent above annual precipitation, whereas others received 20 percent less than average. However, regardless of the annual precipitation accumulation, all the evaluated stations in the SJV 36

Progressive Crop Consultant

saw less than normal precipitation in April (10-90 percent), and far more than normal precipitation in May (300 percent to 1400 percent above normal; Table 2, see page 40 and Figure 2, see page 39).

observed when temperatures range between 56 and 77 F°. Botrytis is normally observed at the beginning and at the end of the growing season.

During spring and early summer, the disease can affect all succulent tissue

Continued on Page 38 In the dry San Joaquin Valley, an above average rainy season, especially when it brings a large snowBeat the Heat & Care pack, is appreciated. for Your Crops with: However, rain and dew after budbreak provide the proper ® conditions for a disease outbreak.

When green tissue, Frost & Freeze water drops, and the Additional Environmental Stress Conditions that the product is useful for: proper temperature • High Temperatures & Extreme Heat • Drought Conditions range, diseases • Transplanting • Drying Winds such as botrytis, A foliar spray that creates a and Phomopsis What is semi-permeable membrane Anti-Stress 550®? can become probover the plant surface. lematic. Humid conditions can also Optimal application period is When to apply one to two weeks prior to the exacerbate powdery Anti-Stress 550®? threat of high heat. mildew infections by promoting spore The coating of Anti-Stress release from its overWhen is Anti-Stress 550® becomes effective when the most effective? winter structures. product has dried on the plant.

Anti-Stress 550

Botrytis

Botrytis is a disease that can develop in temperatures ranging from 32 to 86 F°. However, the optimal growth is

January / February 2020

The drying time of Anti-Stress is the same as water in the same weather conditions.

*One application of Anti-Stress 550® will remain effective 30 to 45 days, dependent on the rate of plant growth, application rate of product and weather conditions.

559.495.0234 • 800.678.7377 polymerag.com • customerservice@polymerag.com Order from your PCA or local Ag Retailer / Crop Protection Supplier

Next year Starts Now Apply KTS®

Orchards consume large amounts of potassium as the crop matures. Almonds remove 91.2 pounds of K2O per 1,000 kernel pounds every season. KTS® is the clear,chloride-free liquid fertilizer with the highest potassium and sulfur content available. KTS® provides 3.0 lbs of K2O and 2.1 lbs of sulfur per gallon available for boosting crop resistance to environmental stress. Applying KTS® is easy as it is 100% soluble and compatible with many fertilizers.

Crop Vitality Specialists can provide assistance regarding application, blending, field studies and technical data.

Start a Conversation today with Your Crop Vitality Specialist Call (800) 525-2803, email info@cropvitality.com or visit CropVitality.com ©2019 Tessenderlo Kerley, Inc. All rights reserved.

KTS® is/a February registered2020 trademark www.progressivecrop.com of Tessenderlo Kerley, Inc. January

37

NAME

CIMIS ID JAN

STRATFORD FRESNO STATE LINCOVE WESTLANDS ARVIN EDISON MERCED PORTERVILLE DELANO

15 80 86 105 125 148 169 182

5.2 5.9 4.6 5.9 7.9 6.3 - 2.9 5.4

FEB

MAR

APR

MAY

JUN

JUL

AUG

SEP

-5.3 -5.0 -3.3 -3.4 -3.0 -4.8 -11.6 NA

-0.5 -0.9 0.6 -0.1 -1.6 -0.5 -5.4 -5.0

4.4 3.3 6.4 7.5 4.4 1.8 2.0 0.3

-6.5 -7.7 -4.6 -3.4 -6.2 -6.7 -7.1 -9.9

1.3 0.0 5.7 6.1 2.6 1.0 2.7 -2.4

-0.4 0.1 3.8 5.0 -0.9 0.8 0.5 -4.9

0.7 0.1 5.0 5.6 -0.1 0.7 1.6 -1.8

-1.4 -2.1 2.2 1.6 -1.0 -1.2 -1.0 -3.8

Table 1. Differences in Monthly Average High Temperatures in SJV against the annual average. NA - Data Not Available.

Continued from Page 36

disease is known as botrytis bunch rot.

where free water is located (leaves, canes, inflorescences and shots), and it is commonly known as botrytis shoot blight. Between veraison and harvest, botrytis can be observed affecting ripened berries; when matured clusters are affected the

For initial infection Phomopsis needs temperatures between 40 and 95 F°, with an optimal initial infection between 60 and 70 F°. Powdery mildew grows in temperatures between 50 to 95F°, with an optimal growth

Phomopsis

temperature between 73 and 86 F°.

All these pathogens also require high humidity conditions for their initial germination and infection. In SJV vineyards botrytis and Phomopsis are not major problems during dry spring seasons. However, the wet and mild 2019 conditions were favorable for pathogen development. This

Continued from Page 38

You don’t report to the front lines.

You live on them.

Too much rain. Too much sun. Weeds. Disease. Insects. Farming is a battle — and the only way to win is to go all in. That applies to us just as much as it applies to you. Our place is at your side, with you in the fight.

Our way of helping is through value-driven crop protection. And the expertise to help you get the most out of it. Learn more at AtticusLLC.com.

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38

Progressive Crop Consultant

©2019 Atticus. Important: Always read and follow label instructions.

January / February 2020

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Temp. F°

Jan

Average Max

Average Min

2019 Max ave.

2019 Min ave

Figure 1. Comparison between 2019 January to September monthly maximum and minimum temperatures and the annual average.

0.5 X or Less

Average

3X or More

Figure 2. Differences between 2019 precipitation and annual average

led to the development of diseases across multiple tissue types, which can be seen in Figure 3(see page 40).

Disease Management

These diseases can be managed through cultural practices and the judicious use of pesticides. Cultural practices start with canopy management to manage a disease under wet conditions. Improved aeration, through canopy management techniques that open the canopy, helps to reduce humidity, allows wet tissue to dry faster, and improves fungicide coverage.

If the amount of rain is significant, adjust irrigation accordingly. Overirrigation, increases vineyard humidity, which can promote the development of fungal infections. Another cultural practice is to have a proper nutrition plan.

Excessive use of nitrogen can result in a plant with succulent tissues that are more easily infected by pathogens.

Also important is to use fungicides with wide spectrum efficacy. These products usually work as preventive and have contact activity. For these reasons, sprayer calibration is key, and the products need to be applied before infection takes place.

Continued on Page 41 January / February 2020

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39

LOCATION Stra�ord Annual Ave. Fresno State Annual Ave. Lincove REC Annual Ave. Westlands Annual Ave. Arvin-Edison Annual Ave. Merced Annual Ave. Delano Annual Ave. Porterville Annual Ave.

STATION ID

JAN

FEB

MAR

APR

MAY

JUN

JUL

AUG

SEP

TOTAL

15

1.17 1.54 2.96 2.28 1.73 1.93 0.82 1.97 0.2 1.14 2.27 2.6 1.12 1.3 1.75 2.43

1.52 1.46 3.63 2.01 3.5 1.85 1.43 1.93 1.01 1.22 4.14 2.36 0 1.3 2.51 2.19

1 1.61 1.51 2.48 2.54 2.01 0.89 1.46 1.85 1.22 2.38 2.09 2.11 1.42 0.83 2.19

0.45 0.55 0.49 1.02 0.62 0.94 0.34 0.67 0.08 0.51 0.03 0.94 0.11 0.67 0.11 1.14

2.94 0.31 2.41 0.55 1.92 0.35 1.42 0.47 2.86 0.2 2.26 0.55 1.85 0.2 1.9 0.4

0 0.08 0 0.24 0 0.16 0 0.08 0 0.08 0 0.08 0 0.12 0 0.14

0 0 0 0.04 0 0 0 0.04 0 0 0 0 0 0 0 0.01

0 0.04 0 0.04 0 0 0.01 0.04 0 0.04 0 0.04 0 0.04 0 0

0 0.31 0 0.31 0 0.16 0 0.24 0 0.08 0.07 0.16 0 0.08 0.01 0.2

7.08 5.9 11 8.97 10.31 7.4 4.91 6.9 6 4.49 11.15 8.82 5.19 5.13 7.11 8.7

80 86 105 125 182 148 169

Table 2. Monthly precipitation observed in 2019 vs annual average precipitation (in).

A

B

C

D

Figure 3. Botrytis shoot blight damage on different plant tissues. A) Nodes, B) Leaves, C) Clusters and Tendrils, D) Canes

40

Progressive Crop Consultant

January / February 2020

Continued from Page 39 Another important step is to determine if a fungicide spray is needed, check weather conditions periodically, and determine if the forecasted conditions are suitable for the pathogen to infect your crop. If rain and the optimal temperatures described previously are

use a sticker-spreader that is compatible with your selected fungicide.

Prevention

Prevention is the most successful measure to manage a plant disease.

Improve your defensive line by having a good irrigation and nutrition plan.

Check weather forecast in a timely manner and plan sprays accordingly.

Have products that you expect to use in

stock and follow the label instructions.

Keep your spray equipment well maintained and keep spare parts so they can be replaced when needed.

Comments about this article? We want to hear from you. Feel free to email us at article@jcsmarketinginc.com

Prevention is the most successful measure to manage a plant disease. Improve your defensive line by having a good irrigation and nutrition plan.

forecasted, consider spraying at least one day before the predicted rain event.

During normal conditions soft chemistries and multisite fungicides are sprayed every 10 days. However, if conditions are conductive for disease development, consider reducing the interval to seven days if the label allows you to do so. When considering stylet oil as a preventive, be sure that temperatures above 90 F° won’t occur in the days after its application and that sulfur won’t be sprayed during the next two weeks after the oil application.

Once infection takes place, the use of synthetic fungicides is advised for non-organic growers. Follow the label instructions and remember to rotate mode of action (FRAC groups) to reduce resistance development.

Under severe disease pressure, check your label to see if the interval can be reduced to 10 days. If rain is expected,

January / February 2020

www.progressivecrop.com

41

West Region

Certified Crop Advisor Update

By JEROME PIER | PhD, CCA, PCA, North Valley Agronomist, Nutrien Ag Solutions,

Chair of the West Region Certified Crop Advisor Program

G

reetings from the new Chair of the Board of West Region Certified Crop Advisors (WRCCA), Jerome Pier. I am taking over from J.W. Lemons, who did a great job helping us with big changes in program administration and opened the door to a new opportunity. But first, some background on the program.

The West Region Certified Crop Advisor program covers California and Arizona and is the largest chapter in North America, with over 1,400 CCA’s. The program is a chapter of the American Society of Agronomy (ASA) in Madison, Wisconsin. The ASA manages certification testing, tracks CCA hours, provides continuing education and manages the international Certified Crop Advisor (CCA) program. The WRCCA is responsible for locally promoting the CCA program, maintaining the CA/AZ regional certification exam, credential review and many other regional activities.

WRCCA membership has grown rapidly since 2012, thanks to the tireless work of ICCA of the Year, Allan 42

Progressive Crop Consultant

Romander, who, sadly, passed away in March of 2019. Past Chair of WRCCA, Fred Strauss, has assumed the duties of marketing the program. An important factor that pushed the growth of the program was the California State Regional Water Quality Control Board recognizing the nutrient and irrigation expertise of the CCA as technical service providers capable of writing nitrogen management plans to reduce the potential for nitrate contamination of groundwater.

Speaking of everything going on-line, the week of February 7, 2020 will be the second time the CCA exam will be given by on-line proctor.

On-line proctoring improves accessibility to those who live in remote areas and wish to take the exam.

WRCCA changed administrators from CAPCA to CalAgJobs, LLC. in 2019.

The Board is enjoying working with Miranda Driver, who has smoothly taken over the day-to-day responsibilities of running the program.

There is news regarding N Management Certification for California. UC Finally, before JW Lemons handed over Cooperative Extension received a CA the Chair’s gavel, he started working Department of Food and Ag Fertilizer with JCS Marketing, who publishes Research and Education grant to move this periodical, to see where our two the nitrogen management certification organizations can assist one another. to a specialty category of the CCA This past September, we co-hosted program. This means that instead of at- the inaugural Crop Consultant tending a one-and-a-half-day training Conference in Visalia, CA, and it was to become certified, one would take the a success. We are looking to continue course on-line and pass an exam. The that relationship, and look forward to last training conference will take place bringing the conference back to Visalia this March 3 and 4, 2020 in Fresno. in September of 2020. Stay tuned!

See CAPCA.com for more details. The certification will move on-line in 2021. Comments about this article? We want to hear from you. Feel free to email us at article@jcsmarketinginc.com

January / February 2020

September 17-18, 2020 Visalia, California New This Year Extended DPR and CCA Topics

Pre-Register at: progressivecrop.com/conference

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at Bloom and Petal Fall

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INCREASE PLANT GROWTH AND VIGOR DURING THIS CRITICAL TIME

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Benefits of

Trial Results for 2019

Bioavailable nutrients to enhance and support photosynthesis Inc Increased photosynthesis stimulates energy production for improved plant and root dev development Can be tank mixed and applied with Grower Standard foliar program

B Sure®

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Boo Boosts plant metabolism, increases photosynthesis and stimulates plant growth and plant vigor

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Enhan Enhances crop quality and yield under both favorable and stressful growth conditions.

Improves plant • growth and vigor abiotic • Supports stress tolerance

Available Through Your Local Retailer B Sure® is a liquid nutrient solution derived by microbial fermentation that increases the activity of multiple critical metabolic pathways in the crop.

Premier Product for Conventional and Organic 44

Progressive Crop Consultant

Agrinos.com

January / February 2020

Growers