Diseases, Pests and Beneficial organisms of of
Strawberry, Raspberry, Blueberry
and
Explanations of the fact sheets
T
his guide provides, for each of the three crops (strawberry, raspberry and blueberry), two series of factsheets, one on diseases and one on pests. A third series of factsheets deals with beneficial organisms in all three crops.
Diseases and pests The factsheets generally include the following information: English name (and synonym, if any) French name Latin name (and synonym, if any) Type of organism (fungus, bacteria or other) in the case of diseases Order: Family, in the case of pests Pictogram indicating risk, frequency and distribution (see table on opposite page). The mention “varietal� indicates that certain cultivars are more susceptible to the disease. Illustration of the main location of symptoms on the plants Size and appearance of the pest at various stages of development Description of the symptoms and damage Problems that should not be confused with the disease or pest Life cycle of the pest Conditions favourable to development Host plants (pests) Timing and method of scouting Best practices xxii
Risk, frequency and distribution – Explanation of pictograms Risk associated with the presence of the disease or pest
Frequency of the problem
Indicates that there is a hazard, risk of harm to crops or risk of a negative effect on crop development Indicates that it is important to be vigilant and watch for the appearance and development of the problem
Extent of the problem in the field ( )
•
1 dot: Isolated problem R: Rare O: Occasional F: Frequent ?: Frequency unknown in Quebec
Indicates that there is no risk or impact on the crop or crop yield
2 dots: Localized problem, but present at more than one location 3 or 4 dots: Problem that can spread throughout the field
interpretation Examples : F
Problem needs to be monitored, is frequent and can spread throughout the field
R
Problem can cause considerable damage when present but occurs rarely and is localized and scattered (at more than one site in the field)
O
Problem does not pose a risk to the crop, appears only occasionally and is isolated.
Beneficial organisms Beneficial organisms, or beneficials, are grouped according to the order (Acari, Coleoptera, Diptera, etc.) and family that they belong to. The following information is generally provided within these categories: Genus and species (where applicable) Size and appearance at various stages of development Insects and other organisms on which the beneficial organism feeds xxiii
Life cycle Practices for promoting the development of the beneficial organism
Other symbols Organism not visible to the naked eye (primarily mites) Organism commercially available (beneficials)
xxiv
PESTS
STRAWBERRY
F
Strawberry bud weevil Anthonome du fraisier Anthonomus signatus Coleoptera: CurculionidĂŚ
A
Size Adult: 2.5 mm Larva: 0.3–0.6 mm Egg: 0.5 mm
Appearance Egg: Whitish (C). Larva: Creamy white, C-shaped body; legless; brown head (B). Adult: Globular body with a long snout (rostrum) that measures almost half the body length (A). Red-brown elytra with two large, round, black median spots that are sometimes rimmed with white scales.
Damage Peduncles and flower buds cleanly cut (D).
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STRAWBERRY
PESTS
B
C
Life cycle  One generation per year. Adults overwinter at the base of hedgerows, in mulch and sheltered places, inside or outside the strawberry field. In May, females bore a hole in the flower bud and lay an egg there. They then cut off the peduncle, which dries out, and the bud drops to the ground. Adults can also eat the flower bud and pierce holes in the sepals. Larvae feed on the flower bud for approximately three weeks. Three larval stages. Adults emerge from the bud in midsummer and feed on the pollen of other host flowers in the fall before seeking an overwintering site.
Favourable conditions  Populations increase as the strawberry field ages. Plants growing under covers or at the edges of fields are at risk.
Host plants Wild strawberry, raspberry, blackberry, blueberry, Parthenocissus (Virginia creeper).
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STRAWBERRY
PESTS
D
Scouting  Adults are particularly active at the end of the day (after 6 p.m.), in calm, dry, sunny weather (temperature above 16°C). Starting when buds become visible and continuing to the end of the flowering period, tap flower clusters over a container, and count the number of adults and cut-off buds. Freshly cut buds (still green) indicate a high risk. Since damage appears suddenly, it is recommended that scouting take place at least twice a week during the flowering period.
Timing of controls The appearance of holes in the sepals (E) indicates an imminent risk. Initiate control as soon as cutE off flower buds or weevils appear, particularly when good weather is forecasted. Treatment can also be initiated at the threshold of three weevils or cut-off buds per 50 taps.
Best practices Do not keep strawberry fields in production for more than two years. Rotate crops far away from strawberry fields in production. Remove weeds growing in and around strawberry fields, particularly pollen-generating plants. Look for damage and respond rapidly. Photos A and B: Bernard Drouin, MAPAQ; C: Pierre Lachance, MAPAQ; D and E: Liette Lambert, MAPAQ
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PESTS
Crickets
F
RASPBERRY
Grillons Snowy tree cricket (grillon de Fulton) Œcanthus fultoni Four-spotted tree cricket (grillon à quatre points) Œcanthus quadripunctatus Black-horned tree cricket (grillon à cornes noires) Œcanthus nigricornis
Orthoptera : Gryllidæ
A
Size Adult: 20–25 mm Larva: 6–25 mm
Appearance Egg: Cylindrical; cream-coloured or yellowish (A). Laid in symmetrical rows inside canes. Larva: Upon emergence (B), the young larva is pale yellow and almost transparent. Slender, smooth body. The more mature larva resembles the adult but without wings (C). Adult: Elongate. Yellowish to pale green. Long legs. Welldeveloped hind femurs. At rest, wings lie flat against the body. Antennae almost twice as long as the body. The male is slender (D), while the female is rounded (D).
167
PESTS
RASPBERRY
Damage The female chews the bark and inserts rows of eggs (E, F). These punctures prevent sap from flowing up and weaken the cane. In the spring, the leaves and fruits can continue to develop, but the affected canes dry out (G, H) before the fruits reach maturity. The canes also break easily at the weak point where the oviposition holes have been pierced.
Do not confuse The damage with canes dried out by frost, broken by winds or infected with the fungus Phytophthora (no characteristic oviposition holes). B
The insect with the larvae of plant bugs or leafhoppers (short antennae), adult field crickets (black), or locusts and grasshoppers (larger and stouter).
Life cycle C
Male
Female
One generation per year. Eggs are laid in August and September and overwinter inside canes. Each row can contain up to 80 eggs. Eggs hatch in June. Young larvae feed on leaves throughout the summer and can also feed on aphids and other small insects. Five larval stages before the adult stage in August. Starting in mid-August, during the mating season, males emit a highpitched noise in the evening and at night.
Best practices  Prune affected canes in the spring, before hatching occurs, and immediately burn the prunings.
D 168
RASPBERRY
PESTS
E
F
G
H Photos A, B, D, E, F, G and H: Liette Lambert, MAPAQ; C: Ginette H. Laplante, MAPAQ
169
DISEASES
B LU E B E R RY
R
Viral diseases Maladies virales Viruses
I 
n North America, a number of viruses infect blueberry and can cause a significant reduction in productivity of susceptible cultivars. In Quebec, however, only a few viral diseases have been diagnosed, the most recent being blueberry scorch virus (BIScV). The most frequently encountered virus in blueberry fields in Quebec is tomato ringspot virus (ToRSV). Several cultivars are very susceptible to this virus. It is therefore advisable to destroy these plants and plant a tolerant or resistant cultivar. This virus is transmitted by soil nematodes, Xiphinema spp. These roundworms, which are invisible to the naked eye (2 mm long), move very slowly between soil particles through water films. These ectoparasites transmit the virus by perforating the wall of root cells in order to feed. That is why the infection site increases in size very slowly each year (e.g. 1 m in diameter per year).
Symptoms The symptoms of the various viral diseases are provided in the tables on pages 236 to 239.
Do not confuse Damage: Winter frost (more-generalized damage), spring frost (early in the season), anthracnose fruit rot (symptoms on the berries), mummy berry (mummified berries), gray mold (down-like gray fungus), deficiencies in minerals such as boron, potassium or magnesium (slightly more-generalized damage), excessive water inducing iron deficiency (damage localized to areas where water accumulates), June beetles (larvae near roots), phytotoxicity caused by herbicides (e.g. clopyralid, dichlobenil, glyphosate, simazine) or other 230
DISEASES
B LU E B E R RY
chemicals such as fluorine (more-generalized damage without varietal effect), high salinity (generalized damage), various types of leaf spots (rarely cause dwarfing or dieback).
Best practices There is no remedy against viruses, and some cause more damage than others, depending on varietal susceptibility, the type of damage that the viruses cause, and the presence of vectors that can quickly transmit the viruses from plant to plant. All viruses are transmissible through propagation of infected plants by cuttings, hence the importance of obtaining virus-free plants. As a precaution, it is advisable to disinfect tools after pruning suspicious-looking plants. Contamination can be limited by controlling the vectors (nematodes and aphids). Adequate control of weeds, especially dandelion and plantain, is important since these weeds often harbour Xiphinema, which transmits ToRSV. Remove and burn affected plants, including the root system, which can also remain infected. Avoid planting near an infested blueberry field. If in doubt, send a sample to your Provincial or State diagnostic laboratory, if available, accompanied by a soil sample, preferably collected in late May/early June, in order to detect and count nematodes.
231
DISEASES
B LU E B E R RY
Tomato ringspot virus (ToRSV)
A
B
C
D
E
F
G
H
I 232
DISEASES
J
K
L
M
N
O
P
Q
B LU E B E R RY
Blueberry scorch virus (BlScV)
R 233
B LU E B E R RY
DISEASES
Blueberry shoestring virus (BBSSV)
Blueberry leaf mottle virus (BBLMV)
S1
S2
T
Red ringspot virus (RRSV)
234
U
V
W
X
DISEASES
Tobacco ringspot virus (ToRSV)
B LU E B E R RY
Mosaic virus
Z1
Y
Z2
Photos A, B, C, E, F, G, H and I: Liette Lambert, MAPAQ; D: Ginette H. Laplante, MAPAQ; J, K, L, M, N, O, Q and R: Lisa Wegener; P: David Raworth, AAFC; S1, S2, T, U, V, W, X, Y and Z2: Marvin P. Pritts, Cornell University; Z1: Eric Hanson, University of Michigan
235
BENEFICIAL ORGANISMS
Lady beetles, ladybirds Coccinelles Coleoptera : Coccinellidæ
A
Size
B
Adult: 1–10 mm Egg: Eggs laid in clusters (10 to 50 eggs) on foliage (A, B).
Appearance Larva: Resembles a small black crocodile (C), often with spots whose shape and pattern vary depending on the species (C, D). Pupa: Immobile and attached to plants by the tip of the abdomen (E). Adult: Bright colouring, variable depending on the species. Coloured patterns visible a few hours after emergence. The most common lady beetles include the pink-spotted lady beetle (D, F, K), the seven-spotted lady beetle (G), the fourteen-spotted lady beetle (H) and the Asian lady beetle (I). The colour and number of spots on the Asian lady beetle are highly variable, but the species is distinguished by the M- or W-shaped marking on the top of the thorax.
Diet Most species feed primarily on aphids, whereas others, such as Stethorus punctillum, prefer mites, such as spider mites.
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BENEFICIAL ORGANISMS 7 to 10 mm
C
D
E
F
G 4 to 6 mm
H
Life cycle  Lady beetles overwinter in the adult stage, singly or in groups. Some species, such as the pink-spotted lady beetle, gather in large numbers under leaves or in leaf litter, often in woodland edges or under large trees. Others, such as the fourteen-spotted lady beetle (H), are arboreal and are observed in blueberry and raspberry fields. Of the 77 species surveyed in Quebec, the Asian lady beetle, introduced into Louisiana in 1988 and reported in Quebec in 1994, is the only species that has become a pest by moving indoors in the fall to survive the winter and feeding on certain juicy fruits, such as raspberries. A wasp, Dinocampus coccinellae (J), sometimes parasitizes lady beetles, and its pupae can be seen (K) on the underside of the pink-spotted lady beetle’s body.
314
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7 to 10 mm
K
BENEFICIAL ORGANISMS
I
J
L
M
N Adult and pupa
Adult newly emerged from its pupa
Spider mite predatory beetle
Stethorus punctillum spp.
The oval eggs are whitish in colour and turn black immediately prior to emergence of the larvae (L). The pupa is black and hairy, like the adult (M). Upon emergence, the adult is light-coloured (N), darkening O within several hours (O). It is often confused with other small black beetles such as flea beetles, which hop. Under the magnifying glass, flea beetles are hairless, whereas S. punctillum is pubescent. Photos A, C, G and H: Nathalie Laplante, MAPAQ; B, D, E, F, I, K and M: Liette Lambert, MAPAQ; J: Ginette H. Laplante, MAPAQ; L, N and O: Biobest Canada
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