Progressive Crop Consultant - November/December 2017

November/December 2017 Deficit Irrigation of Wine Grape Vineyards Management Options for White Rot, A Persistent Challenge for Onion and Garlic Growers Weedy Rice in California: An Overview Preparing for the Next Phase of the New Worker Protection Standard

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Volume 2 : Issue 6

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

CONTRIBUTING WRITERS & INDUSTRY SUPPORT

IN THIS ISSUE 4

Anthracnose; Is it a Threat to California Pistachios?

8

Deficit Irrigation of Wine Grape Vineyards

16

Trap Crops and Natural Enemies: A Winning Combination in Organically Produced Strawberries

20

Weedy Rice in California: An Overview

24

Remembering Steve Orloff

26

Preparing for the Next Phase of the New Worker Protection Standard

30

Management Options for White Rot, A Persistent Challenge for Onion and Garlic Growers

Whitney Brim-DeForest Robert Sanders

UCCE Rice Advisor

Pest Control Adviser

James R. Hagler

Tom Turini

Postdoctaral Associate

University of California Agriculture and Natural Resources, Fresno County Vegetable Crops Advisor desiccation

Themis J. Michailides

Larry E. Williams

USDA Arid-Land Agricultural Research Center

Paulo Lichtemberg

Project Scientist

Department of Viticulture and Enology | UC-Davis and Kearney Agricultural Research and Extension Center

Diego J. Nieto

Amy Wolfe

Plant Pathologist

Juan Moral

Driscoll’s, Inc.

Charles H. Pickett

MPPA, CFRE President & CEO, AgSafe

CDFA

UC Cooperative Extension Advisory Board Kevin Day

Steven Koike

David Doll

Emily J. Symmes

Dr. Brent Holtz

Kris Tollerup

County Director and UCCE Pomology Farm Advisor, Tulare/Kings County UCCE Farm Advisor, Merced County County Director and UCCE Pomology Farm Advisor, San Joaquin County

UCCE Plant Pathology Farm Advisor, Monterey & Santa Cruz Counties UCCE IPM Advisor, Sacramento Valley UCCE Integrated Pest Management Advisor, Parlier, CA

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.

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November/December 2017

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Anthracnose; Is it aThreat to California Pistachios?

By Themis J. Michailides, Paulo Lichtemberg, Robert Sanders, and Juan Moral

A

nthracnose of pistachio: In July 2016, putative diseased samples were collected from two pistachio (Pistacia vera) orchards in northern California (Glenn County) with black and sunken lesions on leaves and rachises. Samples were of the Red Aleppo, Joley, and Kerman cultivars. Eventually, individual fruit were totally blighted. These

genus infects a large number of plant species, causing a plant disease generally known as “anthracnose” and can be very devastating because under the conducive environmental conditions can cause epidemics on various annual and perennial crops.

Isolations from spore masses of pistachio fruit and the margins of leaf lesions from multiple diseased samples revealed 100 percent Colletotrichum species recovery from samples the cultivar

Photo 1

fruit blight symptoms looked different from the Botryosphaeria (Bot) panicle and shoot blight and did not bear any characteristic pycnidia of Botryosphaeriaceae fungi. Instead some of the fruit lesions developed slimy, pink ooze by harvest time. Lesions on the leaves were black and angular and also some developed the same slimy, pink ooze on the surface (Photo 1). Examination of the ooze under a compound microscope revealed masses of elliptical, one-cell conidia, characteristic of the fungal pathogen Colletotrichum. This fungal 4

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Colletotrichum

November/December 2017

(cv.) Red Aleppo and 18 percent from samples of the cv. Kerman in the first orchard. In the second orchard, 9 percent of the isolations from fruit lesions of cv.

Red Aleppo and 100 percent of isolations from small spots in panicles were Colletotrichum species. Also, 40 percent of the fruit lesions produced B. dothidea, an indication that the conditions were conducive to both of these diseases in the summer of 2016. By early August lesions showed on fruit and leaves of cv.

Joly, which was also planted in the first orchard, and isolations from fruit and leaf lesions of this cultivar also produced Colletotrichum species at in the majority of isolations.

In Australia and China, the anthracnose of pistachio has been reported to cause significant yield losses, ranging from 25 percent to up 50 percent in years with wet spring and summer (Yang et al., 2012; Hall et al., 2014).

In California, it is considered a new discovery. Specifically, a 50 percent destruction of the Australian pistachios was reported following the very wet summer of 2010. The occurrence of this severe disease in a couple of orchards in Butte County reminds us of how the devastating Botryosphaeria panicle and shoot blight started in a pistachio orchard in northern California, and in about 12 years the disease became a devastating epidemic on pistachio throughout the state.

History Interestingly, anthracnose of pistachio was first found in a commercial orchard in Glenn County, in mid-July 1998 and by early September 1998 in a Kerman orchard in Tulare County,

2015, and when the practice of checking Botryosphaeria levels in orchards by performing the bud monitoring bioassay (BUDMON) has become a routine test, sporadically Colleotrichum spp. have been isolated recovered from the plated dormant buds, suggesting that the fungus was present in some pistachio orchards.

In the summer 2015, Colletotrichum species were isolated from trunk cankers of pistachios declining mainly due to Phytophthora infections in a com-

mercial orchard with heavy (heavy clay soils!) soil. However, the 2016 symptoms on cv. Red Aleppo were very severe and destroyed almost 50 percent of the yield of this cultivar. Initially the cvs. Kerman and Joley in the same orchard had lighter disease levels, but about two to three weeks before harvest the cv. Joley pistachios developed severe anthracnose symptoms on the clusters, similar to the disease of cv. Red Aleppo. In contrast, the nearby Kerman trees were still lightly infected by harvest, suggesting that perhaps this cultivar is more tolerant to the anthracnose than the cvs. Red Aleppo and Joly.

Symptoms Initial symptoms appear as dark black circular or angular sunken lesions on the fruit and angular lesions on the leaves of about 5 mm in diameter. These lesions on both fruit and leaves expand in size and produce characteristic slimy pink sporulation (photo 2). When there are rains in the spring, the pathogen can

Photo 2

following the wet spring of 1998. This year (1998) was one of the years when Botryosphaeria panicle and shoot blight and the anthracnose of almond developed to epidemic levels in California pistachios. In this occasion, infected fruit were found covered with pink, initially slimy, then becoming powdery sporulation. The species C. gloeosporioides was morphologically identified as the causal agent, but no further investigations were pursued at that time since the disease did not spread following 1998. In the meantime in 2001, the disease was found and described in the pistachio cv. Sirora in Australia and attributed to the fungus C. acutatum. In 2004 and again in 2010, anthracnose symptoms were observed on fruit, leaves, and rachises in an orchard in Tulare County.

In 2010 and following the excess of rain and flooding in pistachio growing areas of Australia, the pistachio industry reported a 70 percent loss of the yearly crop. This tremendous yield destruction was attributed mainly to anthracnose, but also to some degree to Botryosphaeria panicle and shoot blight at a time when the mature crop was close to harvest and warm rains were in excess.

In California though during 2001 to

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Continued from Page 5 also kill young taxianthies of pistachio (photo 3) and sometimes the tips of young and tender shoots. However, most of the damage is mainly because the fungus causes blighting of mature clusters resulting in mold and stained nuts.

Causal Agents In 2016, two isolates from Tulare County and five isolates from Glenn County were reidentified initially to belong in the C. acutatum complex and C. boninense complex groups, based on morphological characters. Using molecular techniques though, the two isolates from the Kerman orchard in Tulare County were identified as C. karstii, while the five isolates from the Red Aleppo pistachios in the Glenn County orchard were identified as C. fioriniae.

Because pistachio growers apply different kinds of fungicides on pistachio to control Bot and Alternaria blights, it is most likely that the disease epidemic in the orchards in Glenn County was a result of resistance selection among the Colletotrichum populations, which is frequent for this fungal genus.

In order to understand the anthracnose disease cycle of pistachio in California, we will need to initiate proactive studies on managing anthracnose and the status of fungicide resistance in Colletotrichum populations in pistachio.

Epidemiology and Management

Photo 3

Because Colletotrichum spp. produce slimy masses of one cell spores into a mucilaginous matrix, it requires rain and/or sprinkler irrigation to spread. In general, Colletotrichum species are able to grow from 50º to 85º F with optimum temperature for growth 75º F. Therefore, conditions in California pistachio orchards can be conducive to the diseases if inoculum and sufficient rains were present. Interestingly, new foliage that develops as a second flash after the rainy period is devoid of infection, although fruit can be infected by latent infections, which are established infections without showing any symptoms initially, but symptoms will develop later in season as the fruit matures before harvest.

A fungicide trial was established in the spring of 2017 where fungicides 6

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were applied at label recommended label rates. The fungicides used included Merivon, KPhite, Inspire Super, and Tilt applied four times at almost monthly intervals starting at shell hardening (21 May) to July 20. All the fungicides resulted in lower levels of blighted fruit than the blighted fruit collected from untreated trees (control).This is the first fungicide efficacy trial against anthracnose of pistachio. We hope to include more fungicides in future trials in order to determine whether fungicides registered against Botryosphaeria panicle and shoot blight show also efficacy against the anthracnose.

To answer the question whether anthracnose of pistachio could be a threat to the California pistachio industry, we can only say, that cv. Kerman is not com-

November/December 2017

pletely resistant to infection, although it is more resistant than the greatly susceptible Red Aleppo, and Joley cultivars. Fortunately, not very many acres of these cultivars are planted in California.

However, when we have excess of rains in the spring growers will need to monitor their fields for unusual symptoms of anthracnose. It does not take very long for a pathogen such as the anthracnose pathogen to reach epidemic levels, as it was the case with the anthracnose of almonds in California several years ago.

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

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Deficit Irrigation of Wine

Grape Vineyards

By Larry E. Williams | Department of Viticulture and Enology UC-Davis and Kearney Agricultural Research and Extension Center

T

he majority of grapevines (Vitis vinifera L.) grown world-wide are cultivated in Mediterranean type climates having warm to hot temperatures and little rainfall during the summer.

The cultivation of grapevines in arid and semi-arid regions of high evaporative demand would indicate that water stored in the soil profile would more than likely be insufficient to meet a vineyard’s consumptive water use. Therefore, supplemental irrigation is necessary if one is to produce a harvestable crop of high quality even during years with average or above average rainfall. In general, vines receiving no supplemental water or that are deficit irrigated will have less vegetative growth, smaller berries and lower yields than vines that are irrigated or irrigated with greater amounts of water (Williams 2010, 2012, 2014b; Williams et al., 1994; Williams et al., 2010a, 2010b; Williams and Matthews, 1990). Deficit irrigation and/or moderate vine water stress has been associated with increased fruit quality, especially for red, wine grape cultivars (Williams and Heymann, 2017; Williams and Matthews, 1990; Williams et al., 1994).

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The initiation of irrigation each year is dependent upon the amount of water in the soil profile; a function of rainfall amount, soil type and rooting depth.

Several methods can be used to determine when to start irrigating (Williams, 2017). One can measure the depletion of water in the soil profile using various methods. Once a critical soil moisture value has been reached, seasonal irrigation would commence. One can use plant-based methods to determine when to start irrigating. This would include the measurement of vine water status (such as midday leaf water potential), leaf stomatal conductance, canopy temperature or thermal imaging and remote sensing.

Again, when a pre-determined critical value had been reached, irrigation would commence. I generally start irrigating vineyards in the San Joaquin Valley when midday leaf water potential drops to -1.0 MPa (-10 bars) and in coastal vineyards when it drops to -1.2 MPa (-12 bars) or slightly lower (more negative).

Once the decision has been made to irrigate there are several methods with which to deficit irrigate vineyards.

November/December 2017

Sustained deficit irrigation (SDI) is the practice of purposely deficit irrigating beginning with the first irrigation and irrigating such throughout the remainder of the growing season. Regulated deficit irrigation (RDI) is the practice of purposely creating water deficits during specific times of the season to conserve water while minimizing or eliminating negative impacts on yield or crop revenue. The timing of RDI in vineyards is usually associated with phenological events of the vine such as between berry set and veraison (berry softening/color change) or veraison and harvest. Both SDI and RDI are based upon knowing what full evapotranspiration (ETc) for the vineyard is and then irrigating at some fraction of that amount once irrigation commences.

One last technique used to deficit irrigate vineyards is called Partial Rootzone Drying (PRD). It is an irrigation regime whereby vines are watered on one side of the vine’s trunk (receiving 50 percent the amount of water of the

Continued on Page 10

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Continued from Page 8 control treatment (generally full ETc)) during a two-week period and then irrigating the next two weeks on the other side of the vine. During the two-week period roots on the non-irrigated side of the vine would experience water deficits.

Normally two drip lines are placed down a row with one emitter on one side of the vine’s trunk and a second emitter (in the other drip line) on the other side of the vine’s trunk. However, based upon my experience (see Table 1) and that of Gu et al. (2004) the effect of PRD on vine growth and productivity was no different

balance technique and lysimeters (Allen et al. 1998). Crop coefficients have been developed on Thompson Seedless grapevines grown in a weighing lysimeter at the Kearney Agricultural Research and Extension (KARE) Center and farmed as raisin grapes (Williams et al., 2003a; 2003b) or as table grapes (Williams and Ayars, 2005a). Row spacing for the vineyard was ~ 3.5 m (11.5 ft.), a 0.6 m (24 in.) crossarm was used and canopy type a sprawl. The maximum Kc values obtained (0.95 to 1.15) across years for these vines were greater than those previously published for raisin or table

that the Kc was a linear function of the amount of shade (also referred to as fraction of ground cover by others) measured beneath the lysimeter vines at solar noon. The relationship was: Kc = -0.007 + 0.017x

(Equation 2)

where x is the percent of the ground shaded beneath the canopy (a whole number) per area allocated to an individual vine within the vineyard at solar noon. Others have also found that the Kc was a linear function of the fraction of ground cover with a slope (0.016 to 0.0.20) similar to that given in Equation 2 (Ayars et al., 2003; Ferreira et al., 2012; López-Urrea et al., 2012; Picón-Toro et al., 2012). López-Urrea et al. (2012) concluded that measuring canoTable 1. The effects of applied water amounts at 56 and 112% of estimated ETc on berry weight, soluble py cover is a reliable solids and yield measured on Cabernet Sauvignon. The grapevines were grown at J. Lohr vineyards near approach to estimate Kc Paso Robles. Both sustained deficit irrigation (SDI) and partial rootzone drying (PRD) were employed as values in grapevines and deficit irrigation strategies. Values are the means across the four-year study with those values within a column that the use of growing followed by a different letter significantly different from one another. degree-days should improve the precision grapes. The seasonal Kc values were than irrigating at 50 percent of full ETc of the estimate by removing year to expressed as a function of calendar day (using SDI). In addition, Sadras (2009) year variation in crop development. The and degree-days (base of 10˚C) from concluded that the economic justificausefulness of this technique to derive tion for the use of PRD was only suitable budbreak. By using degree-days, it was Kc values for other crops is expanding anticipated that the crop coefficients dein a few rare conditions.

(Allen and Pereira, 2009). veloped near Fresno could be adapted to One means to estimate ETc for use in other locations where date of budbreak Williams and Ayars (2005b) cona deficit irrigation management program may differ. The author has also develcluded that it was the orientation of the oped seasonal would be to use the following equation: Kc values for Chardonnay ETc = ETo * Kc (Equation 1) vines grown in the Carneros where ETo is reference ET and Kc is district of Napa the crop coefficient (Allen et al., 1998).

Reference ET is a measure of evaporative Valley and trained to a VSP demand and can be obtained from the California Irrigation Management Infor- trellis on 2.13 mation System (CIMIS) or other entities. m (7 ft.) rows using the soil The Kc is the fraction of water used by water balance a specific crop compared to that of ETo method (Wilat a given location. The above equation liams, 2014a). predicts ETc under standard conditions The seasonal where no limitations are placed on crop progression and growth or ET due to water shortage, maximum Kc crop density or disease, weed, insect values (0.74) or salinity pressures (Doorenboos and developed for that vineyard differed Pruitt, 1977). canopy in space and not the actual leaf from those for Thompson Seedless area per vine or leaf area index (LAI) grapevines due to differences in trellis Crop coefficients are derived from that determined vine water use. Doorentype and row spacing. measurements of ETc which can be bos and Pruitt (1977) concluded that determined from energy balance and Williams and Ayars (2005b) found microclimatological methods, soil water Continued on Page 12

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Continued from Page 10 the Kc values for vineyards would vary considerably due to cultural practices (i.e. differences due to row spacing, trellis type, pruning pattern and differences in growth among cultivars and perhaps scions grafted onto different rootstocks).

Based upon the above it would appear that the seasonal Kc should differ due to trellis used and row spacing, factors not considered for Kc values used in the past. Beginning in 2000, shaded areas under different trellis systems were measured in vineyards around California. The wine grape trellises included the lyre, GDC (Geneva Double Curtain), VSP (Vertical shoot positioning trellis) and vertically split canopies (Scott Henry and Smart-Dyson trellis systems). Several additional trellis systems were also measured such as the ‘California Sprawl’, overhead trellises and others using crossarms of various lengths. Shaded areas under the vines were measured with the use of a digital camera at solar noon, software was used to calculate shade in the image (Williams and Ayars, 2005b) and the percentage of shade per area allotted per vine in the vineyard converted

to a crop coefficient using Equation 2, page 10.

The Kc values for different trellises, estimated from shaded area measurements in various vineyards across years did differ from one another. For example, the shaded area at full canopy (and calculated maximum Kc) for a Lyre trellis was greater than that of a VSP trellis at the same row spacing. This would

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The results from the data collected in 2000 and subsequent years/studies (Williams, 2010, 2012, 2014a; Williams and Fidelibus, 2016; Williams and Heymann, 2017) indicate that the derivation of crop coefficients from percent shaded area is a

Table 2. The effect of row spacing on estimated seasonal Kc values for a VSP trellis system, a California Sprawl type canopy, quadrilateral cordon trained vines and Lyre (or ‘V’) type canopies. The x value in the equation is degree-days (base of 10°C) from a starting point. The ‘e’ value in the equation is 2.71828. Note that row spacing only changes the numerator in the equation, the maximum Kc value.

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area measurements at Carneros (VSP trellis) were similar to those developed earlier via the soil water budget method (Williams, 2014a).

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be expected as there was more canopy per unit land area for the Lyre system. The Kc values increased as the season progressed for all trellises. Maximum canopy size was obtained between 750 and 1000 degree-days (base of 10°C) after a starting point, except for VSP trellises which took longer to achieve maximum canopy size. Lastly, estimated Kc values derived from shaded

reliable means to estimate vineyard ETc. Best estimates of the seasonal crop coefficients for various wine grape trellises and row spacings are summarized in Table 2. The equations in Table 2 derive the Kc using degree-days (>10°C) from a starting point (budbreak). Note the degree-days used in the equations are from the Celsius scale with a base of 10°C. The use of Fahrenheit temperature (base of 50°F) will not work with these equations (the UC-IPM website will calculate degree-days using the Celsius scale).

Since budbreak generally occurs around the middle of March in the San Joaquin Valley, March 15th is used as the starting point. Budbreak in the coastal valleys of California generally occurs around

could also be used to calculate a Kc for use April 1st. In the Coachella Valley, January in a deficit irrigation strategy using the dual 15th is used as the starting point since that Kc method: is when table grapes initiate growth there.

Apart from the VSP trellis, the shaded areas Kc = KsKcb + Ke (Equation 4) measured beneath the canopy of east/west and north/south rows at solar noon are where Ks is a dimensionless ‘stress’ coeffisimilar to one another. The seasonal crop cient whose value can be set by the grower. coefficients I’ve developed for a VSP trellis The seasonal crop coefficients for wine given in Table 2 (page 12) are valid for most row directions. Using a 3D model that grapes in Allen and Pereira (2009) include an implicit Ks factor of 0.7. calculates light interception by the canopy (Iandolino et al. 2013) it was demonstrated that a VSP trellised vineyard on true north/south rows will intercept greater light on a daily basis than a similar vineyard with true east/west rows. Lastly, the values presented in this table do not account for cover crop water use in the vineyard. A study at the KARE Center demonstrated that water Figure 1. Leaf water potential measured across 8 growing seasons use of vines within (1994 – 2001) taken close to harvest each year (dates varied from 28 rows planted with Aug. to 21 Sept). Irrigation commenced when midday Ψ1 was ~ -1.0 cover crops was MPa (-10 bars) each year. Values are the means across years (vines 40 percent greater grafted onto two rootstocks, 5C and 110R) + standard error (n = 4 than vines in rows for the 0, 0.25, 0.75 and 1.25 treatments and 8 for the 0.5 and 1.0 without a cover treatments). crop (LE Williams, unpublished data).

Crop ET can be derived from the ‘dual crop coefficient’ method (Allen et al., 1998): ETc = (Kcb + Ke) * ETo (Equation3) where Kcb is the basal crop coefficient (the portion of ETc due to plant transpiration) and Ke is the coefficient used for soil evaporation. The use of this method is more complicated than that of Equation 1 (page 10). One must calculate daily Ke values for soil evaporation.

Do grape growers need to apply water at 100 percent of estimated ET? It would depend upon production goals. Once full ETc is calculated via Equation 1 (page 10) or 3 then deficit irrigation practices can be used such that a fraction of full ETc is applied to the vines either throughout the growing season (SDI) or during specific phenological stages (RDI). The following equation

If one uses appropriate Kc values, based upon degree-days and considering trellis and row spacing, then applied water amounts at various fractions of ETc should result in similar vine water status readings from one year to the next. Such was the case in a study conducted on Chardonnay grapevines where estimated, seasonal ETc varied from a high of 500 mm (~ 20 in.) one year to a low of 350 mm (~13.5 in.) (Williams, 2014a). Leaf water potential values of vines irrigated at a specific fraction of estimated ETc were very similar at harvest from one year to the next across the eight-year study (Figure 1, page 13).

This indicates that if your goal is to grow vines with a uniform degree and pattern of water stress every season, then scheduling vineyard irrigation using reliable crop coefficients is beneficial.

Continued on Page 14 November/December 2017

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13

and that growth during this period is due to both cell division and cell elongation.

Water deficits will reduce cell division.

Berry growth after veraison is due only to cell elongation.

Continued from Page 13 I have shown across many years and locations that one can deficit irrigate grapevines such that water use efficiency is increased and yields can be maintained for wine, raisin and table grapes (Williams, 2010; 2012; 2014b; Williams and Heymann, 2016; Williams et al., 2010b). For example, Williams et al. (2010b) demonstrated that yield of Thompson Seedless was maximized at applied water amounts between 60 and 80 percent of full ETc, with the actual amount dependent upon year. There were no significant differences in yield of Chardonnay grown in Carneros, a cool grape growing region, at applied water amounts from 25 to 125 percent of estimated ETc (Williams 2014b). Lastly, berry size and yields of Perlette and Flame Seedless grapevines grown in the Coachella Valley were maximized when deficit irrigation at 50 percent of estimated ETc (RDI technique) was not initiated until after berry set had occurred (unpublished data). In general, applied water amounts at 50 percent or less of ETc throughout the growing season (SDI strategy) will reduce yields of grapevines (Table 1, page 10).

It is thought that berry size may be an important quality factor in red wine grapes. Smaller berry size may be preferred since the skin contains most of the color and flavor producing compounds.

Deficit irrigated vines will have smaller berries than well-watered vines (Table 1, page 10). Vines experiencing water deficits during the period between berry set and veraison will have smaller berries at harvest than vines experiencing the same degree of stress but only between veraison and harvest. On average, 65 to 75 percent of the final berry size is determined between set and veraison

14

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Sugar concentration in grape berries will determine the alcohol content in the wine. In general, sugar accumulation is less affected by water deficits than berry growth (Table 1, page 10).

Excessive stress may delay the accumulation of sugars. A study was conducted on 17 red, wine grape cultivars at the KARE Center for four years. Irrigation treatments included: A.) applied water at 100 percent of estimated ETc between berry set and veraison and then no applied water to harvest, B.) no applied water between berry set and veraison and then applied water at 50 percent of estimated ETc through harvest and the last treatment was C.) applied water at 50 percent of estimated ETc season long. Across all years of the study and cultivars, sugar accumulation occurred more rapidly for treatment A (late deficit) than for treatment B (early deficit). In fact, the early deficit treatment delayed the start of veraison for several of the cultivars.

Final sugar concentration in the berries of treatment A was somewhat greater than that for vines irrigated at 50 percent of ETc season long.

A moderate decrease in organic acids of the fruit is generally found where soil or vine water status indicates water stress. The effect of water deficits on the decrease of acids in grape berries is due more to a reduction in malic acid, than for tartaric acid. In the study on 17, red wine grape cultivars at the KARE Center, vines which received the early deficit treatment (B – no applied water between set and veraison, 50 percent ETc thereafter) or the 50 percent ETc season long treatment had much less titratable acidity when measured at harvest than vines in the late deficit treatment (A – full ETc between set and veraison, no water after that). Matthews and Anderson (1988) found that malic acid in the fruit of their early deficit irrigation treatment was significantly less than that in the fruit of

November/December 2017

their late deficit irrigation treatment.

Deficit irrigated vines usually have greater total phenols and anthocyanins than those receiving more applied water (Williams and Heymann, 2017; Williams and Matthews, 1990). Matthews and Anderson (1988) reported that both early and late season deficits were equally effective in increasing total phenolic content compared to vines receiving more applied water. The changes in the composition of the fruit due to water deficits are reflected in the wine (Matthews et al., 1990; Williams and Heymann, 2017).

The effects of early and late water deficits on total anthocyanins in the wine of vines grown at the KARE Center are less conclusive. Total anthocyanins in wines made from fruit in 2013 for the early deficit irrigation treatment was 14 percent greater than those from the late deficit treatment while the reverse was true in 2014 (the late deficit was 18 percent greater than that of the early deficit treatment). Wine total anthocyanins of the 50 percent season long treatment were intermediate between the other two treatments both years.

The degree of vine stress one imposes, and its timing can be dependent upon location. Soil water deficits have less of an effect on productivity in a cooler growing region (Williams 2014b) than a hot region (Williams, 2010; Williams et al., 2010b). Based upon the red, wine grape cultivar study conducted at the KARE Center, the lack of irrigation between set and veraison delayed/decreased sugar accumulation and acid content in the fruit and return fruitfulness (cluster number the following growing season) and final yield to a greater extent than the lack of applied water from veraison to harvest. In addition, the frequency of irrigation events could possibly mitigate the effects of deficit irrigation on productivity under certain conditions (L.E. Williams, unpublished data). Therefore, such information should be taken into account when devising a deficit irrigation strategy for vineyards.

For a full list of citations, please contact Larry E. Williams at: lewilliams@ucanr.edu Comments about this article? We want to hear from you. Feel free to email us at article@jcsmarketinginc.com

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TRAP CROPS AND NATURAL ENEMIES:

A Winning Combination in Organically Produced Strawberries

By Charlie H. Pickett | California Department of Food & Agriculture Diego J. Nieto | Driscoll’s, Inc. James R. Hagler | USDA Arid-Land Agricultural Research Center

L

ygus bug has long been a pest in a wide range of field early season flower buds. and seed crops in California, including strawberry.

Since then, scientists have Damage is caused by its piercing—sucking mouthparts ascribed this attraction to (Fig. 1) that cause odor cues emitted by harm to flower buds alfalfa flowers and or flowers, leading plant scents released to yield reducwhen lygus bugs feed tions. Lygus bug on the plant. feeding on developing strawberries Similar to cotton, results in distorted strawberries are not a fruit, known as highly preferred plant “cat-facing” (Fig. for lygus bugs, but 2), and ultimately a can nonetheless suffer reduction in fresh considerable feeding market yield. Until damage (Fig. 2) if recently, its control more attractive host has been limited plants are not nearby.

Fig. 1. Mouthparts of a Lygus bug. Photo by Studies on the incorto multiple applications of chemical Collin Brown. poration of alfalfa insecticides and physical removal with tractor-mounted vacuums. This article addresses two, parallel, complementary efforts to provide a biologically-based and organically approved strategy to maintain lygus bugs below economically damaging levels. One involves the interplanting of alfalfa within a strawberry field (trap cropping), while the other utilizes beneficial insects to reduce populations of lygus bug (biological control).

Lygus bug’s attraction to, and preference for, alfalfa has long been understood. In the 1960’s, researchers at the University of California studied alfalfa’s use as a trap crop (i.e., plants that are highly preferred by a pest when compared with associated field crops) to draw lygus bugs away from cotton, thereby reducing feeding damage on 16

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trap crops into strawberry fields in the Monterey Bay region began in the early 2000’s (Fig. 3, page 17).

Results from these studies have shown that alfalfa is compatible with strawberry production. That is, it has similar irrigation, fertilization, and plastic mulching requirements. Also, alfalfa trap crops will flower from spring through fall (with routine and staggered cuttings), which provides the sustained floral attraction needed to draw in multiple pest generations during strawberry harvests that can persist for seven months. Since lygus bug populations are highly concentrated in and immediately around trap crops, scouting (i.e., monitoring) becomes more

Fig. 2. Cat facing caused by lygus bug feeding. Photo by C. H. Pickett

November/December 2017

ries, both with respect to the number of harvestable berries per plant and the percent of lygus bug-damaged fruit.

tained within one row of alfalfa. Recent research findings examining the gut contents of generalist predators collected from strawberry farms found that: 1) a wide array of predators consumed lygus High lygus bug concenbug, including four types of insects and trations in alfalfa trap crops seven types of spiders; and, 2) a higher also provide unique percentage of opportunities to predators had improve the biologieaten lygus bugs cal control rendered in alfalfa, when by lygus bug natural compared with enemies. Common adjacent strawpredators found in berry rows. For California strawberinstance, the Fig. 3. Trap crop of alfalfa intercropped with organiries, such as spiders minute pirate cally produced strawberries. Photo by C. H. Pickett. and predaceous bug (Fig. 4), insects are generalist which was the convenient and physical management feeders, meaning they will most common of the pest via tractor mounted vacuprey upon almost anything.

Fig. 4. The predator, minute pirate predator in this uming becomes targeted and efficient.

As predation choices are often bug on strawberry flower. Photo by study, conIn a study conducted from 2002-2004, influenced by prey availability, Jason Buhler. sumed lygus vacuumed alfalfa trap crops were shown the manner in which prey are bugs more often to decrease lygus bug feeding damage by distributed throughout a field may affect in alfalfa (16 percent of collected speci2.5 percent in adjacent strawberry rows, predation rates. For instance, lygus bugs mens) relative to strawberry (7 percent relative to vacuumed strawberry rows in strawberry that are widely dispersed of collected specimens). without a trap crop. A recent study from at lower densities throughout a larger 2012-2015 indicated fresh market yield area may elicit lower predation rates Continued on Page 18 improvements in trap-cropped strawber- than high densities of lygus bugs con-

November/December 2017

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17

Continued from Page 17

within strawberry fields plays an important role in anchoring wasp populations.

Historically, the beneficial insect Similar to the predator-prey dynamics community in California strawberry has discussed earlier, as parasitism opporbeen largely limited to generalist predatunities are limited in strawberry fields tors. However, a specialist natural enemy that are annually replanted and contain was introduced in relatively low lygus 2002 to provide more bug densities, the efficient biological high lygus bug host control. A Europedensities in strips of an parasitic wasp, alfalfa allow wasp known as Peristenus populations to relictus, which prigrow and stabilize. marily targets lygus Using techniques bugs was released that allowed us to near Monterey Bay. track wasp moveThis wasp reproducment, we docues by laying an egg mented differing inside the body of a wasp responses Fig. 5. The parasitic wasp Peristenus live immature lygus to varying lygus relictus inserting one of its eggs inside a lygus bug nymph. Photo by C. H. Pickett. densities in strawbug (Fig. 5). The wasp egg hatches and berry. Specifically, subsequently kills its when lygus bug host as it matures to an adult by feeding abundance in strawberry was low, this on the pest’s internal organs and fluids. wasp remained in the alfalfa trap crop; After several releases of this parasitic wasp over a two year period into weedy non-crop vegetation (e.g., mustard and radish) and insecticide-free alfalfa trap crops, both of which provided abundant lygus bug populations, it has become permanently established in the Monterey Bay area. Moreover, it has begun to spread throughout the state. For example, in 2011 it was found as far south as Atascadero, over 100 miles away from the original release site. In 2016-2017, releases and recoveries of the wasp have been made in Ventura County.

Efforts have been taken to monitor and document the long term impact of this wasp on lygus populations. Research has revealed that lygus bug populations at three of four release sites has dropped by 76 to 94 percent between 2002 and 2015. In particular, wasp-pest population dynamics at an organic trap-cropped strawberry farm yielded several important findings. First, parasitism and lygus bug densities were closely correlated.

As lygus numbers increased, so did the number, and impact, of wasps. Second, lygus bugs were more evenly distributed in the strawberry field, indicating they might cause less feeding damage. Finally, pest populations decreased significantly and remained below economically damaging levels at several study sites over this 13 year period (Fig. 6).

The presence of alfalfa trap crops 18

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of the Monterey Bay region. Peristenus relictus, the parasitoid that has become widely established was collected from southern Europe. A second population of Peristenus digoneutis from the north coast of France has been collected and released in 2015 and 2016. Release plots of alfalfa will be sampled this summer to see if they survived the winter.

Summary

Until recently, there have been few biological alternatives to pesticides for controlling lygus bugs. We now know that alfalfa trap crops can attract lygus bug populations away from strawberries and concentrate lygus bug natural enemies. Beneficial arthropods found in strawberry and alfalfa include native predators (insects and spiders) and the introduced lygus-specific parasitic wasp, Peristenus relictus. The copious amounts of prey (lygus) and natural enemies provided by alfalfa trap crops can stabilize and anchor predator and parasitoid populations in strawberry systems.

Long term studies have found that fresh market yields are improved in trapcropped strawberry when compared to strawberry alone. Since Fig. 6. Decrease in lygus bugs over time. Monterey Bay, California. the introduction of the alfalfa trap crop method and the however, when pest densities were high exotic wasps in 2002, lygus populations in strawberry, it readily moved from have steadily declined. Moreover, lygus alfalfa and into neighboring strawberry parasitism rates have increased. Our rows. results provide information on how to develop an organically approved lygus Efforts are underway to establish a bug control strategy and a pesticide-free second wasp species that is closely relatworking environment for farm laborers. ed to P. relictus. Peristenus digoneutis is also from Europe and may compliment P. relictus. This wasp species was released along with P. relictus over 14 years ago, Comments about this article? We want but none established permanent popula- to hear from you. Feel free to email us at tions. One possibility is that the populaarticle@jcsmarketinginc.com tion of wasps coming from central Europe may not be adapted to the climate

November/December 2017

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Weedy Rice in California: An Overview

By Whitney Brim-DeForest | UCCE Rice Advisor

Introduction

W

eedy rice, also known as “red rice”, has recently reappeared as an issue of concern for California rice growers. Although an important weed of rice in almost every rice-growing region of the world, California was thought to be free of weedy rice in recent decades.

This was attributed to a strong seed certification program and a predominantly water-seeded and flooded rice culture.

However, in the early days of commercial rice cultivation in California (up until the 1940’s), surveys by the University of California found weedy rice present in most rice seed samples. With the widespread adoption of certified seed in the 1950’s, reports of it largely disappeared from that point on. It reappeared in the early 2000s, but acreage was limited to just a few fields. Follow-up surveys in subsequent years failed to find additional infested fields.

Then in 2015, the California Crop Improvement Association reported increasing numbers of “off-type” rice, found not in seed fields, but in commercial fields near seed fields. During the 2016 growing season, University of California Cooperative Extension Rice Advisors began to receive reports of “grass20

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like” weeds that could not be controlled with rice herbicides. After conducting field visits, it became apparent that the problem was not grass, but weedy rice.

By the end of the 2016 season, it was found to have infested over 10,000 acres across every major rice-growing county in California.

What is it?

Weedy rice is the same species as cultivated rice (both are Oryza sativa L.), which makes it both difficult to manage as well as difficult to identify.

One of the most difficult management aspects for California rice growers, who rely heavily on herbicides for weed control, is the lack of chemical control options for weedy rice. Since weedy rice and cultivated rice are the same species, any herbicide that controls weedy rice, will also “control” or kill cultivated rice plants. For growers, this means resorting to a set of cultural practices which can be both expensive and difficult to implement.

Identification is also Weedy rice can be distin-

November/December 2017

guished from cultivated rice by two defining biological characteristics: seed dormancy and shattering of the mature panicle. If a seed has dormancy, it will not always germinate when planted in the spring, even if all conditions are suitable for its growth. When planted, cultivated rice varieties have germination rates of well-above 90 percent, whereas weedy rice populations will have low germination rates, sometimes close to 0 percent. As for shattering, a cultivated rice variety does not shatter and will retain all its seed on the panicle until it is

Photo 1 Watergrass (left) and rice (right). Notice the ligule and auricle easily identifiable on the rice plant.

Photo credit: University of California

run through a combine or harvester. Weedy rice plants will shatter (i.e. not retain seed on the panicle) and will start to drop seed onto the soil surface well before the cultivated rice is ready to harvest. This ensures that there is seed in the soil seedbank for the following season.

There are many other characteristics that are common to weedy rice populations but since the traits are also shared by some cultivated varieties, they are not always useful in determining if a rice plant is weedy.

They are: 1) colored or red bran (but some varieties are also colored or red); 2) pubescence or “hairiness” of the leaves (some varieties also have this trait); 3) light-colored leaves; and 4) tall leaf height. If a plant has these characteristics, it is possible, but not certain, that it is weedy rice. The only way to positively determine that a plant is weedy rice and not another contaminant (such as a varietal mixture) is either by genetic testing, or by waiting until the plant is mature, and testing for shattering and dormancy.

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Although the level of weedy rice infestation in California is still relatively low (only about 2 percent of the total rice acreage), it has the potential to affect both individual growers as well as the rice industry as a whole. For growers with heavily infested fields, yield reductions can be high, as a large proportion of the rice seed that would normally have gone into the harvester is instead lost onto the soil surface through shattering. Research to quantify those losses is ongoing. After harvest, during the milling process, weedy rice with a red pericarp (bran) must be milled further to remove the reddish color. This can result in a higher percentage of broken rice, reducing the quality of the milled rice.

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Identification Weedy rice is difficult to identify, because it is the same exact species as cultivated rice. It also looks similar to some of our most important grass species in rice: those in the watergrass complex (Echinochloa

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Continued from Page 21 spp.). The best time to identify it is to wait until after all grass herbicide applications have been made. At that point, it is important to personally inspect any remaining plants: 1) Check to see if there is a ligule and auricle (Photo 1, page 20) 2) If a ligule and auricle are absent, the plant is a watergrass species 3) If a ligule and auricle are present, the plant might be weedy rice, and it is best to call a UCCE (University of California Cooperative Extension) Rice Advisor for further identification and testing There are currently five populations of weedy rice identified in California, which are grouped both by their physical characteristics as well as by their genetics (Table 1):

Best Management Practices The UCCE has put together a list of Best Management Practices for weedy rice, focused on removing as much seed from the field as possible, as well limiting the amount of seed being put back into the soil for the next season. As always, prevention is of utmost importance. The full document can be found at: www. caweedyrice.com under “Best Management Practices for Weedy Rice”. Some of the most important practices: Prevention: 1) Plant certified seed, or seed that is part of the new Quality Assurance program, which will prevent the introduction of contaminated seed into the field 2) Clean all equipment moving into a previously un-infested field, especially

if equipment is coming from the Southern USA Management: 1) Limit tillage both in the spring and fall: tillage pushes seed deep into the soil seedbank, prolonging the time-period that the field will be infested 2) Remove as much seed and potential seed production from the field as possible: a. Utilize flushing and a stale seedbed, either on a fallow field, or before planting in the spring. This will encourage weedy rice germination, and then a burn-down herbicide can be used to kill any germinated seedlings. b. Hand-pull larger weedy rice plants from the field (before they have headed) c. Once plants have headed, cut off

TYPE 1

TYPE 2

TYPE 3

TYPE 4

TYPE 5

Awnless

Awnless

Awned

Awned

Awnless

Red pericarp (bran)

Red pericarp (bran) Red pericarp (bran) Red pericarp (bran) Red pericarp (bran)

High shattering

High shattering

High shattering

High shattering

Variable shattering (depends on population)

High dormancy (low Low dormancy germination) (high germination)

High dormancy (low germination)

High dormancy (low germination)

Variable dormancy (depends on population)

Straw-hulled

Straw-hulled

Black-hulled

Straw-hulled

Gold-hulled

Table 1. Physical and biological characteristics of weedy rice populations in California by type (data by Dr. Teresa De Leon, 2017).

Reporting and Sample Collection If a grower or Pest Control Adviser suspects a weedy rice infestation, the UCCE is asking that they contact a UCCE Rice Advisor to inspect the plant in the field. Plants should not be removed from the field or transported, to minimize the spread of seed and contaminated soil.

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November/December 2017

Weedy rice Type 1 (Photo credit: Dana Dickey, California Rice Research Board)

seed heads into bucket, to prevent shattering seeds onto the soil surface d. In the interest of removing as much seed as possible from the field, do not use a stripper header for harvest, as it tends to drop seed onto the soil surface e. Note: No spot-treatment herbicides are currently approved for use in California

Weedy rice Type 2 (Photo credit: Dana Dickey, California Rice Research Board)

Weedy rice Type 3 (Photo credit: Dana Dickey, California Rice Research Board)

3) Flood the field during the winter, to maximize the decomposition of the seed. This is most effective when there has been little to no fall tillage and most of the seed is at or near the soil surface.

Status in 2017 From early in the season, growers and PCA’s were on the lookout for and reporting suspected plants. UCCE Rice Advisors received many calls over the course of the season, but only about 25 percent of the suspected plants were confirmed to be weedy rice. The other 75 percent of suspected plants were varietal contaminants (seed that was mixed with another variety) or volunteers from the previous season. Growers with known infestations have been working directly with UCCE Advisors and their PCA’s to reduce the infestations in their fields.

The latest information and resources on weedy rice can be found at: www. caweedyrice.com, which is a joint effort between the California Rice Commis-

sion and the UCCE. Research funded by the Rice Research Board is ongoing, and results will be forthcoming on the weedy rice website.

Comments about this article?

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

Weedy rice Type 4 (Photo credit: Dana Dickey, California Rice Research Board)

Weedy rice Type 5 (photo credit: Dana Dickey, California Rice Research Board).

November/December 2017

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23

REMEMBERING Steve Orloff Photo courtesy of UC ANR.

T

waves, literally, and became an expert surfer—a passion he continued to cultivate throughout his life.

his memoriam is reprinted courtesy of Rob Wilson, center director and farm advisor at the Intermountain Research and Extension Center in Tulelake, California.

Steve spent several years in Central America serving in the Peace Corps, primarily El Salvador, where he worked with marginal farmers struggling to survive in this tropical, crowded region. He met his wife-to-be in Honduras during this period.

After graduation with an MS in Crop Sciences from San Luis Obispo, Steve took the University of California Farm Advisor position at Lancaster, CA.

Family and friends mourned the loss of Steve Orloff, University of California Cooperative Extension Farm Advisor, who passed away October 3, 2017 from cancer.

Steve Orloff advised many farmers, industry members and conducted research on many crops, including alfalfa.

Steve is remembered for his great sense of humor, his dedication to his family, his friendship to many, and his immense service to agricultural science.

He served as a University of California Cooperative Extension Farm Advisor for more than 33 years.

The alfalfa industry, in particular rues his loss, since he contributed greatly to this important California crop.

A True Agronomist. Steve Orloff was a true agronomist with broad knowledge and in-depth expertise related to most fields of agriculture science. He published hundreds of articles reporting on his original research related to pest management, irrigation, harvest management fertilization and variety

24

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selection. Steve worked with many crops including alfalfa, grass hays, small grains, onions, and several specialty crops. His accomplishments played a vital role in progressing California agriculture and helping solve many regional problems related to pests, water conservation, and economic stability. The publications “Intermountain Alfalfa Management’ which he led in the 1990s, and “Irrigated Alfalfa Management for Desert and Mediterranean Zones” (2008) which he made significant contributions on are considered the leading nationwide references to management of alfalfa.

From Southern California. Steve grew up in Lancaster, California, where he learned to appreciate agriculture in the high-desert communities of Los Angeles County. It was also in Southern California that Steve learned to surf the

November/December 2017

Although he had said that the job required a steep learning curve, he was aided by the many experts in crop production in the region, farmers and ranchers, PCAs, and crop specialists at UC Davis and UC Riverside who appreciated his dedication to his scientific solutions to important problems.

To the Northern Mountains. After making significant contributions in the high desert region, Steve made a momentous change in his life-to move his young family, now with three children, from the high desert of Los Angeles County to the high mountains of California, to take a position in agronomic crops at the UC Cooperative Extension office in Yreka, Siskiyou County, where he has lived for more than 24 years. In many respects, this was a good fit—given the dominance of alfalfa as a major

crop, the confluence of crop rotations with small grains, pasture, and specialty crops, and the importance of irrigation in a dry environment.

There Steve quickly established himself as a regional expert on many crops including alfalfa, conducting significant research on-farm as well as at the University of California Intermountain Research and Extension Center at Tulelake, CA. Steve had as special interest in weed management. His work on the control of dodder, a major weed in alfalfa production in California, during the 1980s became the gold standard for management strategies for this important and difficult parasitic weed.

knowledge was appreciated not only by many farmers and industry members in California, but throughout the nation, as well as internationally. He has received many awards including the Jim Kuhn Service Award from the California Alfalfa & Forage Association in 2011.

intelligence, but his ability to light up a room and to engage on nearly every subject. He deeply loved his family and community and will be sorely missed by all. Steve is survived by his wife Islia, sons Rob, Michael and Danny, mother Carol and sisters Lisa and Diane.

The most important attribute of Steve, though were his personal characteristics. He was personal friends to many farmers, industry members and university colleagues. He was valued not only for his accomplishments and

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

More recently he conducted much of the university evaluations with Roundup-Ready alfalfa, including techniques to prevent weed shifts and resistance in this system. His sharp observations and excellent field research also identified a novel crop injury phenomenon in intermountain Roundup-Ready alfalfa in 2015-2017. He continued his field research right up until the time of his recent diagnosis in August, 2017.

Widely Appreciated by Farmers.

Steve was beloved by growers and industry representatives in California, the West, and nationwide due to his robust research program, excellent crop management knowledge, and his great ability to extend information in a fun and easy to understand style. He was a widely sought after speaker at state-wide and regional events, including the Western and California Alfalfa Symposium, Western and California Weed Science Society Conferences, and annual grower meetings in New Mexico, Utah, Nebraska, Washington, Arizona, Idaho, Oregon, and Nevada. He was a regular contributor to research presentations at the UC Intermountain Research and Extension Center, and at UC Davis. His thoughtful analysis and presentation of his own research data was always a highlight of any meeting, including his incorporation of humor that always enlivened the crowd.

Steve gave many talks and conducted programs internationally in alfalfa and agricultural development, including Spain, Romania, Chile, Argentina, China and Mexico. His talent and his in-depth

November/December 2017

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Preparing for the Next Phase of the New Worker Protection Standard

By Amy Wolfe, MPPA, CFRE | President and CEO, AgSafe

O

n January 1, 2016, the United States Environmental Protection Agency (EPA) finalized the revisions to the agriculture worker protection standard (WPS). The WPS is a federal regulation that applies to pesticide handlers and workers in areas where pesticides are used in production agriculture. The Department of Pesticide Regulation, which has pesticide regulation enforcement authority in California, has updated the California Code of Regulations (3CCR) to be consistent with WPS with a few exceptions.

Currently the Department of Pesticide Regulation (DPR) has published text of proposed regulations. The comment period closed last September and an effective date should be announced shortly. In the meantime growers should be preparing for compliance in the following areas: • • • • •

26

Notice of Completed Applications Handler Training Fieldworker Training Fieldworker Decontamination Facilities Field Posting

Progressive Crop Consultant

Notice of Completed Applications: Any person applying pesticides as a pest control business must give the grower notice within 24 hours of application completion. The notice of completion must include the site ID, which can be found on the grower’s pesticide permit, the pesticide name and EPA registration number, any adjuvants used, the start and end dates and times along with the pre-harvest interval (PHI) and the restricted entry interval (REI).

Once given this information, the grower must retain a record of this information and communicate it to his employees.

While the letter of the law may seem like more paperwork, the spirit of the law is to ensure that employees do not enter a treated field and commodities are not harvested prior to the PHI.

Handler Training: Pesticide training for handlers was already a requirement under the existing WPS. With the revisions, there is an increase in the number of training elements and the requirements for trainer

November/December 2017

certification. Under this section growers are required to maintain a written pesticide program that outlines the materials used to train, like DPR’s pesticide safety series which can be found at http://www. cdpr.ca.gov/docs/whs/psisenglish.htm.

The pesticide program must also address the credentials of the trainer. Under the updated WPS, trainers are considered qualified if they are a California certified commercial applicator, California certified private applicator, licensed pest control advisor, or have completed an approved trainer the trainer course. If you are a California DPR license holder, you are qualified to train. However, it is the expectation of DPR that you are aware of the additional training elements and as such, have sought the information needed to provide compliant training.

While the number of training elements have increased, the topics covered are similar just more detailed than before. For example, previous trainings addressed that it is not safe to bring agricultural pesticides home. Now the training must further discuss that

Continued on Page 28

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27

Continued from Page 26 agricultural pesticides are especially dangerous to children and pregnant women.

Annual pesticide trainings should cover topics like hazards, PPE, safe handling and storage, how exposure occurs, decontamination procedures, SDS, emergency medical care, first aid procedures, and heat illness prevention. For a comprehensive list of topics visit, http:// www.cdpr.ca.gov/docs/legbills/ rulepkgs/17-001/17-001.htm. Be sure you are training your handlers (who now have to be at least 18 years old) prior to them handling pesticides, any time you introduce a new pesticide to your schedule, and annually thereafter.

The decontamination supplies cannot be more than quarter mile from fieldworkers, growers must communicate to workers as to where the supplies are

no small or faded signs. This section goes on to note specific language to be included on the sign: skull and cross bones, “DANGER” and “PESTICIDES” in both English and Spanish, and “KEEP OUT” and “NO ENTRY.” If the sign is being used to post a field that has a REI longer than 7 days additional site information is required on the sign.

Even through DPR has not finalized regulations in response to the revised WPS growers can begin tackling items needed for compliance in prepaFieldworker Training: Included in pesticide handler training topics is how to select proper personal protective equipment (PPE) for every pesticide used. Photo ration. These regulations will take some time to Like the handler training, the courtesy of AgSafe. implement, be sure you number of topics covered in fieldare giving yourself and your farming located, and supplies cannot be stored in worker training has also increased. Some operation time to update and adjust. an area that creates another hazard, like of the topics covered are very similar to in a field where the REI has not expired. handler training, with more of an emFor more information about While the requirement is not more than phasis on the locations that workers can pesticide safety or any worker safety, quarter mile, best practice is to have come into contact with pesticide residue. health, human these supplies located as In addition to the topics, the frequency resources, labor close as practical. In a has also increased. Prior to the WPS uprelations, or possible pesticide expodates, fieldworkers needed to be trained food safety issure, quick decontaminaevery five years. The current regulation sues, please vistion can prevent serious now requires this training annually. Init www.agsafe. injuries and illness. cluded in this section now is any worker org, call us at performing early-entry activities must be (209) 526-4400 at least 18 years old. Early entry means Field Postings: or via email entry into a treated field or other area afat safeinfo@ ter the pesticide application is complete, Field posting is not agsafe.org. but before the restricted entry interval a new idea to pesticide or other restrictions on entry for that safety. While we were AgSafe is a pesticide have expired. And again, like used to posting when 501c3 nonprofhandler training, fieldworker training required by label, now it providing needs to be given by a certified trainer. added to this section training, educaFieldworker Decontamination Supplies: is the requirement that tion, outreach there is a field posting and tools in the While decontamination supplies are whenever an application areas of safety, already a requirement for fieldworks, is made with a pesticide Any pesticide with a restricted entry labor relations, one noticeable change is the increase to that has an REI greater interval (REI) greater than 48 hours food safety and the amount of water required. Under than 48 hours. Prior to requires field posting under the updated human rethe revised WPS the following items are 2018 implementation, sources for the required for fieldworker decontaminado a quick check in your Worker Protection Standards. Photo courtesy of AgSafe. food and farmtion supplies: pesticide storage shed ing industries. to determine if you have Since 1991, AgSafe has educated nearany products that would fall into the • 1 gallon of water per employee (3 ly 75,000 employers, supervisors, and greater than 48 hours threshold. If so, gallons per handlers) workers about these critical issues. chat with your PCA about possible alter• Soap (hand sanitizing gels do not meet native products. this requirement) Comments about this article? We want • Single use towels (wet towelettes do not Another element to be aware of in to hear from you. Feel free to email us meet this requirement) this section is the actual posting sign. at article@jcsmarketinginc.com The sign must be readable at 25 feet, so 28

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Management Options for White Rot, A Persistent Challenge for Onion and Garlic Growers

by Tom Turini - University of California Agriculture and Natural Resources | Fresno County Vegetable Crops Advisor desecation desiccation

All photos courtesy of Tom Turini

T

he collapse of onion or garlic plants along with the with a soft rot and the diagnostic poppy seed-like resting structures remains something that producers hope to avoid. The soilborne fungus, Slerotium cepivorum, causes white rot.

The name of this disease is descriptive of the fluffy white mycelium that appears at early stages of disease development and the wet rot that can cause complete loss of the crop. In addition to the white growth of mycelium on the head and neck of the plant, the fungus produces hard, dark resting structures about the size, color and shape of poppy seeds.

These structures, called sclerotia, can survive in the soil for decades in the absence of a suitable host.

San Joaquin Valley within areas with a history of these crops is substantial. The disease has been present for decades and for some production regions within the Valley, the presence of this pathogen has limited the quantity of these crops that are planted. In the past, the primary method of management was identification and avoidance of infested fields.

Now, there are over 20,000 acres infested in the Central San Joaquin Valley. For some growers for which garlic and/or onions are an important component of their program, there are few fields that are not known to be infested; therefore, the avoidance tactic is problematic.

Resting structures or sclerotia will germinate in response to exposure to compounds produced in the root zone of onions, garlic and their close relatives. The host range of this pathogen is limited to these plants. Very few sclerotia per handful of soil can be enough to cause notable losses in these crops. Soil temperature is another factor that drives disease development, with approximately 50o to 75oF favoring sclerotia germination and disease development.

Temperatures favoring disease development occur frequently in a variety of very important garlic and onion production areas.

Researchers have labored on this issue for many years and currently, research efforts are in progress in Central. and Northern California and Oregon with the ultimate goal being development of a reliable program to make production of susceptible crops in a white rot-infested field reliably profitable. A few of the approaches to ultimately be combined that are being investigated includes the use of materials to bring down the inoculum levels in fields, reduce risk by at-planting applications of fungicides and use of site-specific technologies.

Distribution of this pathogen in the

30

Progressive Crop Consultant

had potential utility in management of white rot. As reported by Mike Davis and others, DADS can reduce the quantity of viable sclerotia in the soil by more than 90 percent when applied in the absence of a garlic or onion crop. Because of similarities between DADS and

Research Efforts

DADS is an acronym used to refer to the chemical diallyl disulfide. In 1994,.

Fred Crow reported that this compound

November/December 2017

compounds produced in the root zone of onions and garlic, it stimulates the sclerotia to germinate. After dormancy is

Other materials that may reduce soil inoculum levels are being evaluated. Because the potential of this approach in tricking the resting structure to break dormancy and starve has been demonstrated with DADS, the potential use of other materials containing these compounds are being evaluated. There are several challenges in the application of these materials, one is that the soil temperatures must be correct while the compounds are present in order to trigger germination. Another is that there cannot be volunteer hosts in the field or this may actually lead to an increase in soil inoculum. A big challenge is that these materials must have sufficient levels of active compounds in order to elicit the desired response in the resting structure.

broken, the fungus requires a host but if it germinated in response to a synthetic chemical and there is no host present, it does not have a source of nutrition and it would starve. This is what leads to the reduction of viable inoculum in the soil.

However, DADS is no longer available.

Onion and garlic products may be options for this approach, but as these materials decompose, the compound composition changes and there are inconsistencies in the levels of the biologically active compounds. In studies conducted by Rob Wilson, Jeremiah Dung and Tom Turini, garlic juice has been evaluated in infested soils in Fresno County and in Tulelake, but there has not been a consistent impact in the number of sclerotia nor in yield or quality of the garlic or onions. Michael Qian analyzed this garlic juice and other garlic juice products and found that the active volatile compounds present in garlic juice are as low at 1/10,000 of the level in the DADS product, but these concentrations vary from batch to batch.

Currently, Dr. Qian is working on identification of additional compounds active compounds and methods of increasing these levels in garlic juice.

Fig 1. Early decline symptoms tend to cluster and have general symptoms of desiccation and have a light green to yellow coloring

Fungicides are a component of a management program. Studies conducted by Wilson,

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Continued from Page 31 Crow, Davis, Ferry-Abee, Mueller, Turini and others have provided information regarding details on chemical control. The only consistently efficacious application has been in a 6 inch band over the furrow into which cloves or seed is dropped. Materials with several modes of action have provided control consistently over many studies.

These materials include tebuconazole (Tebuzol or Orius), fludioxonil (Cannonball), and penthiopyrad (Fontelis) or boscalid (Endura).

In a recent Fresno County study conducted under moderate disease pressure, use of these fungicides resulted in yields 32 to 52 percent higher than in the untreated. The challenge with fungicides is that under very high inoculum levels, the materials will fail to provide commercially acceptable levels of control.

Continued on Page 34

Fig 2. Mid to late disease development is characterized by light colored foliage and presence of the dark resting structures on the roots and head.

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November/December 2017

A DV E R T O R I A L

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ROOT HEALTH & TREE LONGEVITY THREAT GROWERS CAN’T SEE

Nematodes, microscopic roundworms barely visible to the naked eye, pose a serious problem for walnut and almond growers. Even with proper sanitation and fumigation practices, nematodes can still become an issue after setting new trees. Nematode populations can build up in the soil, attack tree roots and impact overall tree health.

UNSEEN BUT FIERCE ON

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NEMATODES CAUSED

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MOVENTO® SUPPRESSES RING NEMATODES BY 85% NUMBER OF NEMATODES

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3. Applications of Movento® in established orchards resulted in a reduction of nematode populations.

Movento does offer a nematode management tool that can easily be incorporated into a tree nut grower’s cultural practices.

Trial conducted by Gary Braness, Bayer CropScience, Kerman, CA, 2009–2011.

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Applications of Movento® in established orchards helped result in:

2. If possible, fumigate the soil prior to planting new trees. This will reduce the number of nematodes initially, but will offer only a temporary solution.

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Average yield loss in lbs. per acre is based on California Agricultural Statistics Review, 2014–2015. California Department of Food and Agriculture.

“Nematodes: A Threat to Sustainability of Agriculture,” Satyandra Singh, Bijendra Singh and A.P. Singh.

3 University of California – Cooperative Extension. Department of Agriculture and Resource Economics. UC Davis, 2012.

4 “The Dangers of Nematodes,” Growing Produce – 2012.

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© 2017 Bayer CropScience LP, 2 TW Alexander Drive, Research Triangle Park, NC 27709. Bayer, the Bayer Cross, and Movento are registered trademarks of Bayer. Always read and follow label instructions. Not all products are registered for use in every state. For additional product information, call toll-free 1-866-99-BAYER (1-866-992-2937) or visit our website at www.CropScience.Bayer.us.

November/December 2017

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33

than the entire field.

Importance of Sanitation Regardless of the research efforts that are in progress, there is not going to be a means of managing this pathogen that does not involve substantial expense, so the preferred management strategy, where possible is avoidance of this issue. In addition, avoiding moving soil and plant material from field to field will also reduce the likelihood of introducing other soil-borne issues into your field.

Start with clean planting material: This pathogen can be introduced into an area on infected garlic planting material, so avoid questionable sources of garlic cloves.

Fig 3. Sclerotia, dark colored poppy seed sized resting structures (sclerotia) of the white rot pathogen Sclerotium cepivorum.

Continued from Page 32 Global Positioning Systems have been used to document areas in which above ground symptoms were observed.

Based on those coordinates, soil was sampled and sclerotia densities were recorded in several fields in Fresno County. Sclerotia were detected hundreds of feet from the site at which aboveground symptoms were observed. However, this is attributable to the aggressive tillage program practiced at those sites and in areas where cultural practices differ, this should be reevaluated. In this production area, because fields are commonly 150 acres, the information regarding symptom expression can help to limit the area that will need to be treated, which may be reduced to 20 acres rather

Contaminated equipment may also move inoculum, so ensure that planters, tillage equipment or harvesters are not brought into your field with soil or with plant material on them. Removing dirt an plant material will substantially reduce risk. Even when you are working with rotational crops, the inoculum is still there. Even if it is not equipment associated with susceptible crops: white rot inoculum does not go away, so sclerotia can be moved on lettuce or tomato harvest equipment and risk is higher if a large quantity of mud is being moved with this equipment.

Fig 4. Infection can occur at several stages of plant development.

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Reduction of risk of introduction of this and other soilborne pathogens is critical. Sclerotia are relatively large as compared to most fungal structures and are not likely to be airborne due to their shape and size, but on onion or garlic scales, they can be moved smaller distances. Therefore, there may be movement between fields once it is in a geographic area regardless of sanitation practices. It is not possible to eliminate risk, but by careful attention to equipment moving between fields or from other areas and planting clean garlic, you are greatly reducing the potential of movement of this pathogen into a field that is not infested.

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

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