Insect & Disease Identification Guide For Grapes

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Insect & Disease Identification Guide For Grapes


Agdex#:	231/600
Publication Date:	May 2003
Order#:	03-039
Last Reviewed:	May 2003
History:	(Replaces OMAFRA Factsheet Insect & Disease Identification Guide for Grapes, Order No. 90-200)
Written by:	Neil Carter - OMAFRA; Kevin Ker - KCMS Inc; Dr. Wendy McFadden-Smith - McSmith Agricultural Research Services

Introduction

Early recognition of disease, insect and mite problems in vineyards is important for the prevention of heavy infestations and serious crop losses. The mere presence of a pest does not necessarily mean that control measures are needed. While some diseases, insects or mites may be present every year, seasonal fluctuations in disease severity and insect or mite populations may cause a pest to be a major problem one year and not the next. As a result, the pest complex and the control measures may vary each year. To aid in the management decisions for pest problems, the Disease and Insect Monitoring Guideline contained within this factsheet has been produced to give an overview of activity of the grape pest complex. This factsheet describes the major and minor pests most frequently found on grapes and should be used in conjunction with pictorial factsheets and field guides to help identify pests in grapes. The information may aid growers and industry personnel in identifying disease, insect and mite problems early so that control measures can be implemented before serious problems arise.

How To Use The Disease And Insect Monitoring Guideline For Grapes

Locate the time of year or the growth stage at the top of Table 1, Insect Monitoring Guideline for Grapes and Table 2, Disease Monitoring Guidelines for Grapes. Look down vertically from the time of year or growth stage reference. Any intersection of an imaginary vertical line with a horizontal line indicates that the disease or insect may be present at that time. Once the possible diseases and insects have been identified, refer to Table 3, Disease Information Table and Table 4, Insect Information Table to obtain the symptoms of disease infection and insect damage for those pests specified in the guideline. The information tables are aids in matching the symptoms found in the vineyard to those of a specific disease, insect or mite. Many other kinds of insects may be present in vineyards including many kinds of beneficial insects. This factsheet does not cover all possible insects or insect pests that may be encountered.

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Control

Good management of disease and insect problems involves both cultural and chemical applications. Spring cultivation that buries any debris that may carry overwintering disease and/or insects and may help to reduce the initial population for that season. For both disease and insect control, proper pruning is necessary to allow good spray coverage and, in the case of disease control, good air movement for rapid drying of foliage. In addition to various cultural practices, monitor changes in pest activity with regular scouting throughout the vineyard during the growing season. For the chemical control of pests, consult OMAFRA Publication 360, Fruit Production Recommendations (click here to order). A variety of chemicals are registered for use on major pests, however, fewer and often none are registered for minor pests.

Other OMAFRA Factsheets On Grape Pests

Grape Phylloxera, Order No. 88-125, Click here to order.
Phomopsis Cane and Leaf Spot of Grapes, Order No.90-123, Click here to order.
Downy Mildew of Grape, Order No. 90-125, Click here to order.
Grape Diseases: Corky Bark Disease and Stem Pitting, Order No. 93-027, Click here to order.

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Table 1. Insect Monitoring Guidelines for Grapes

Text equivalent of Table 1

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Table 2. Disease Monitoring Guidelines for Grapes

Text equivalent of Table 2

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**Table 3.** Disease Information Table
Disease	Disease Symptons	Favourable Conditions	Control Measures
Downy Mildew	on young green tissues (i.e. shoots, tendrils, leaves and clusters) small, pale yellow spots on the upper leaf surface with white, fuzzy spore masses directly below spots on the underside; later yellow spots turn brown and white, sporulation becomes dark grey severely infected clusters turn dark and curl to resemble a pig tail	infection requires wet periods and cool to moderate temperatures 18 – 24 ⁰C is the optimum temperature range for disease development	prune and manage canopy to allow good air movement and spray penetration protect new growth with effective fungicides
Powdery Mildew	white to greyish, powdery spore growth is seen on upper and lower leaf surface or on fruit clusters (especially on interior of cluster) inside the upper canopy is the initial site of infection black, pinhead-sized specks (fungus fruiting bodies) appear in late summer	high relative humidity allows sporulation and spore germination warm, non-rainy weather is ideal; prolonged humid conditions also favour growth	prune and manage canopy to allow good air circulation and to reduce shading and humidity in the vineyard spray with fungicide to prevent infection follow fungicide resistance management strategy
Botrytis	greyish or light brown spore growth occurs on dead floral parts or on other dead tissue red-brown lesions appear around veins or in a triangular V-shaped pattern at leaf edges white grapes turn brown and rot while purple grapes turn reddish; berries may split and become covered with tan spores	cool (18–23⁰C) humid weather is necessary for disease initiation grape varieties with tight clusters are very susceptible (berry squeeze or split makes wounds for infection)	allow proper air movement for drying of vines and manage canopy prevent berry damage by pests (e.g. grape berry moth) use preventative fungicide in the suggested resistance management strategy
Black Rot	upper leaf surface will have reddish-brown circular spots with dark brown borders and black dots (pycnidia) in spot centres raised black lesions develop on cluster and leaf stems and on new shoots berries develop a small white dot (1 mm wide) which becomes encircled by a reddish- brown ring later berries dry and shrivel into a blue-black mummy with numerous pycnidia on skin surface	extended wet periods are necessary for spore germination often disease is most serious under prolonged cool, wet conditions around bloom and again in late August through harvest	use protectant fungicides remove infected debris cultivate early in season to bury infected mummies and debris
Phomopsis	yellow spots develop with dark centres which may fall out and give a "shot-hole" appearance dark brown or black spots appear on lower portion of shoots and stems and may coalesce and lengthen to form a patch of diseased tissue (sometimes resembles razor blade nicks) lesions with light brown centers result if lesions crack and heal phomopsis-infected fruit looks similar to black rot infected fruit except symptoms not apparent until veraison	wet grape vines for several days after bud break allow infection cool weather favours fungus growth in early season while shoots are first elongating	remove and destroy or bury diseased and dead wood from vines apply protectant fungicides especially at 2–5 cm growth and 10–15 cm growth
Eutypa Dieback	cupping of leaves along with stunting and chlorosis of shoots occurs during the first 2 months of the growing season leaves show small necrotic spots and tattered edges cankers are seen around old pruning wounds 3–4 yr after the initial infection berries do not size uniformly	pruning wounds in canes are entry points for the fungus weakened canes and heavy rainfall will release spores several years between infection and development of symptoms	prune canes below area of visible symptoms; renew vine with younger shoots that do not show symptoms rogue out vine if infection has reached crown area of plant

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**Table 4.** Insect Information Table
Insect	Damage Caused by Insect	Insect Appearance	Control Measures and References
Grape Berry Moth (GBM)	damage is caused by the larval (caterpillar) stage 1st generation larvae web together buds, flowers and newly-set berries; affected plant parts often drop from vine 2nd generation larvae burrow into green berries near the berry stem or side where berries touch. A purple spot may form around the pin-head size hole. Berries may split, shrivel, become infected by disease, or fall off when damaged 3rd generation larvae can cause direct fruit injury (tunnel directly into one berry and then move from berry to berry within the cluster) and lead to significant disease infection prior to harvest	overwinters as pupae with adults emerging in early May adult moth is 6 mm when fully grown and has a brown body with wings that are grey-blue near the body and cream with brown spots near the tips young larvae have a cream body and dark brown head. As they mature, the larvae become green and then purple with a light brown head when mature larvae are 10 mm long at maturity	remove nearby wild grape and abandoned grapes bury leaf debris on vineyard floor listen to local crop reports for activity patterns and preferred control options refer to OMAFRA factsheets on GBM and Publication 360 for control options mating disruption products for control of GBM affect only this pest
Grape Leafhopper (GLH)	adults and nymphs feed on underside of leaves by sucking leaf cell contents tissue around feeding puncture turns pale and dies feeding injury appears first along leaf veins but later affects whole leaf no thresholds established through research in Ontario	adult GLH are pale yellow with darker yellow lines on forewings and 3 black spots on wings small wedge-shaped insect (3 mm adult) fast moving and active nymphs resemble adults without fully developed wings	overwinters as adult fall cultivation and clean-up of adjacent weedy areas eliminates favourable overwintering sites monitor for activity in early spring starting at first warm days after leaf tissue is present listen to control suggestions on local crop reports
Potato Leafhopper (PLH)	adults and nymphs suck leaf cell contents potato leafhoppers (PLH) also inject a toxin that blocks vascular system of the plant leaves curl upwards and yellow at edges extensive PLH feeding causes leaf edges to turn brown ("hopper burn") damage to grapes often observed after 1st cut in nearby hay fields. Mowing of weeds along roads in June also sends PLH into vineyards no thresholds established through research in Ontario	similar shape to grape leafhopper but all stages of PLH are pale green nymphs move sideways or backwards when disturbed	PLH does not overwinter in Ontario PLH travel from the midwest and southern U.S. under suitable weather conditions monitor for activity in early June listen to control suggestions on local crop reports
Three banded Leafhopper	adults and nymphs feed on underside of leaves by sucking leaf cell contents tissue around feeding puncture turns pale and dies feeding injury appears first along veins but later affects whole leaf heavy infestations can lead to leaf drop no thresholds established through research in Ontario	adult three banded leafhoppers appear similar to grape leafhopper but possess 3 distinct bands across the wings at rest	overwinters as adults monitor for activity in early spring with first warm days after leaf tissue is present listen to control suggestions on local crop reports
Spring Feeding Caterpillar Complex	entire leaves or the interveinal areas of leaves are chewed and webbing may be present on leaves terminal leaves of shoots are webbed together and chewing damage is evident damage is most severe along the peripheries of vineyards and in rows near bushes, woods or weedy areas	3 main species cause damage: 1. eight spotted forester: 3.3 cm larva with orange, yellow, black and white stripes and black spots 2. grape plume moth: 2 cm green larva with white hairs 3. pyramidal fruitworm 3–4 cm green larva with white specks, a whitish or yellow stripe down the back and a pyramid-like hump on its rear	insecticides used for grape berry moth are usually effective against these caterpillars if using GBM mating disruption, specific sprays may be required for spring feeding caterpillars listen to control suggestions on local crop reports
Blossom Midge	flower buds are enlarged with a slightly reddish colour at the base of the flower bud many small larvae (maggots) live in a watery fluid inside the bud and eat the internal flower parts injury is more common in rows next to wooded or weedy areas	larvae are yellowish to reddish larvae complete development, drop to the ground to pupate, and remain inactive until the following spring	generally does not cause economic injury
Phylloxera	green or red fleshy galls, 6–20 mm in diameter, appear on undersurface of leaves and tendrils	young adults are 1 mm long, yellow and non mobile nymphs are inside galls and migrate to young leaf tissue and growing points to establish new colonies	can cause significant injury to young vines such as Baco Noir and other hybrids
Grape Flea Beetle	a few to many buds on a cane may be injured by the adult when it chews through the ends and sides of swelling buds a circular hole is evident in the chewed buds and no shoots are produced damage occurs in rows adjacent to bushes or wooded areas	adult beetle is 5 mm long and has a dark metallic, greenish-blue or steel-blue colour	greatest injury from this pest is during prolonged cool springs with slow bud growth apply insecticide if adult beetles present in damaging numbers early in the season
European Red Mite	leaves become bronze-coloured due to adults and nymphs feeding on leaf underside; photosynthesis is reduced and berry ripening can be affected	adult female is < 0.5 mm with a red to reddish-brown oval body and 8 legs adult male is dull green to brown with a pointed abdomen and is smaller than female	high populations may require treatment with an effective miticide – good coverage with sufficient water volume is important
Erineum Mite	white, indented galls appear on the lower leaf surface and pink or reddish blisters develop directly above these galls; the galls later turn yellow and then reddish-brown abnormal growth of new shoots, downward curling of leaves and premature leaf drop occur in severe cases, terminal buds are destroyed and secondary shoots develop	adults are whitish, wormlike and about 0.2 mm long eggs are oval and white large numbers of adults exist in colonies	sulphur, when used for early season disease suppresion, also helps control erineum mite often found on Riesling and Vidal in areas near bush lots and areas with tall weeds

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For more information:
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E-mail: ag.info.omafra@ontario.ca

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