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Grape IPM in the Northeast

Immediate Prebloom

IPM practices to be implemented

Monitoring required

see discussion below.

Inoculum available for infection

see discussion below.


 

Postinfection Disease Management Protocol

Continue to monitor weather conditions for infection periods of black rot and powdery mildew. Vineyards containing varieties susceptible to downy mildew should have a protectant fungicide applied (mancozeb, captan, or Ridomil) at the immediate prebloom period. Consult Postinfection Spray Protocol for Niagara and Certain Hybrid Varieties for details on postinfection disease management strategies for susceptible varieties. Some weather equipment is sold with downy mildew models that are generally based on sporulation and infection requirements for secondary inoculum. The weather parameter of relative humidity is needed to use these models. There are no postinfection models currently available to predict primary infection of downy mildew that have been proven effective in New York State IPM implementation projects.

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Monitoring required

Grape Leafhopper (also available as a 230k pdf file)
Monitoring is only required in vineyards rated as being at low risk for grape berry moth using the Grape Berry Moth Risk Assessment protocol. Vineyards rated as being at high or intermediate risk using the protocol should automatically receive an insecticide application at 10 days postbloom. Feeding in the spring by overwintering grape leafhopper adults will be found primarily on the leaves of suckers before it can be seen in the vine canopy. Leaf damage is visible as yellow or white dots that sometimes run together into streaks. Adults and nymphs feed by piercing leaves with their needle-like mouth parts and removing the contents of leaf cells. While minor leaf damage can be found in most years, heavy infestations requiring treatment at this time are uncommon, and moderate damage from this pest will not affect yield or quality significantly. Heavy leafhopper feeding damage at this time indicates that leafhopper populations may potentially build up to damaging levels later in the season. Monitoring vineyards for visible signs of leafhopper feeding in the canopy just prior to bloom will give an indication of whether a 10-day postbloom application of insecticide is necessary. For complete information on leafhopper scouting, consult New York's Food and Life Sciences Bulletin 138, Risk Assessment of Grape Berry Moth and Guidelines for Management of the Eastern Grape Leafhopper (appendix 2) (717k pdf file).

Rose Chafer
The rose chafer is a sporadic pest. It should be of concern only if a vineyard has a history of problems or in years with a mild winter followed by a warm, dry spring. Damage from this pest generally occurs to the leaves and flower clusters during the bloom period. Damaging populations are usually associated with light, sandy soil.

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Inoculum available for infection

Black Rot 548k pdf file and Powdery Mildew 490k pdf file
The immediate prebloom period through postbloom is typically the time when the majority of primary inoculum is available for both black rot and powdery mildew. Eliminating a fungicide application at this time can result in economically damaging disease levels.

Phomopsis Cane and Leaf Spot 277k pdf file
Rachises are susceptible to this disease from the time they first become visible until after pea-size fruit have formed. Infected rachises and shoots develop black, elongated lesions that often split the green tissue. Numerous lesions give the surface a blackened, scabby appearance. Fruit infections occur primarily from bloom through shatter, then remain dormant until harvest. Severe fruit rot can develop at harvest if the bloom period was excessively wet and fungicidal protection was absent, particularly in high-risk vineyards. Infected berries have a brown coloration and become covered with black, pimple-like fruiting bodies.

Downy Mildew 300k pdf file
Rainfall is the most important environmental factor promoting downy mildew epidemics. Infected leaves on vineyard floors harbor overwintering structures (oospores). If water is present and temperatures are at least 50°F, oospores germinate and release swimming spores (zoospores). Zoospores are rain splashed onto susceptible tissue and swim to stomata, where infection occurs. Sporulation occurs at night, at temperatures above 55°F and relative humidity above 95 percent, on the undersides of leaves. Infection occurs through stomates to initiate secondary infections. Management of downy mildew with properly timed, protectant fungicides, as with the primary-season protectant disease management protocol, is currently the only reliable method of control. The immediate prebloom period is the most important for managing primary inoculum of downy mildew. See table 2 (69k pdf file) for varietal susceptibility to this disease.

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