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Grape IPM in the Northeast

3- to 6-inch Shoot Growth

IPM practices to be implemented:

Monitoring Required:

See discussion below.

Inoculum Available for Infection:

See discussion below.

Current IPM disease management strategies are aimed at reducing primary infections through the use of the sterol-inhibitor class of fungicides (Bayleton, Nova, and Rubigan). By reducing primary infections, the amount of inoculum available to create repeating cycles of secondary infections is drastically reduced. Limiting the use of sterol inhibitors (SIs) to early in the season helps with resistance management by eliminating their application to existing infections. For complete information on IPM disease management strategies for Concord, Niagara, Vinifera, and French hybrids please refer to appendix 1.


 

Disease Management Protocol for Vinifera and Highly susceptible Hybrid Cultivars

Management of powdery mildew and Phomopsis Cane and Leaf Spot should begin at one inch of shoot growth for varieties that are very susceptible to these diseases. See table 2 (69k pdf file) on page 32 for information on varietal susceptibility. This is necessary only when disease problems during the previous growing season indicate an abundance of overwintering inoculum.

Researchers in the Department of Plant Pathology, New York State Agricultural Experiment Station, Geneva, have developed a postinfection disease management protocol that has been successfully implemented for management of black rot and powdery mildew in Concord vineyards. A similar trial in a Riesling block has also shown management of black rot and powdery mildew to be comparable to conventional programs. The postinfection program is discussed in IPM Disease Management Protocols.

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Postinfection Disease Management

Management of powdery mildew, black rot, and Phomopsis Cane and Leaf Spot should begin at three inches of shoot growth for varieties that are moderately susceptible to powdery mildew if disease problems during the previous growing season indicate an abundance of overwintering inoculum. Concord vineyards with little powdery mildew or black rot the previous year should start the postinfection protocol at the 10-inch shoot growth stage. Please refer to IPM Disease Management Protocols. for details on this protocol.

One disadvantage of the postinfection program is that there are no postinfection fungicides that will manage Phomopsis Cane and Leaf Spot, and protectant applications for Phomopsis are not a part of the protocol. While low levels of Phomopsis are managed using this protocol, the Primary-season Protectant Disease Management Strategy should be used for vineyards with a history of severe Phomopsis infections.

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Monitoring Required

Grape Cane Gallmaker (also available as a 177k pdf file)
The grape cane gallmaker is considered a secondary pest except in a few localized areas that experience heavy damage from it in some years. Galls produced by this pest have not been shown to affect the vigor and growth of the vine, but shoots may break at gall sites. Yield typically is not affected, as galls form on the ends of shoots, past nodes containing grape clusters. In vineyards with extremely heavy infestations, galls may form between the shoot base and fruit clusters, affecting yield. Vineyards with a history of heavy infestations may benefit from an insecticide application to prevent egg laying and gall formation. Galls can be removed by summer pruning before early August to reduce the overwintering population, usually without affecting yield.

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Inoculum Available

Powdery Mildew 490k pdf file
In the northeastern United States, the powdery mildew fungus overwinters as tiny, black, fruiting bodies (cleistothecia). Spring rains of approximately 0.1 inch or more cause cleistothecia to split and forcibly eject ascospores. These ascospores germinate and infect green tissue if the temperature is 46·F or greater. The resulting fungal colonies produce secondary spores (conidia), which are wind-dispersed to susceptible plant parts. Once they are present, conidia cause secondary infections under a wide variety of environmental conditions, and do not require rain to do so. This cycle of secondary infection, spore production, and dispersal is repeated many times throughout a season. Commercial management of powdery mildew is based on the use of fungicides. See table 2 (69k pdf file) for varietal susceptibility to this disease.

Black Rot 548k pdf file
Black rot is considered one of the most serious diseases of grapes in the eastern United States. The black rot fungus overwinters in mummified fruit on the vine and the vineyard floor. Spores within overwintering structures on the mummies are mature and ready for discharge beginning about one to three weeks after bud break. Spring rains trigger release of spores from mummies, and air currents carry these spores to susceptible tissue. Infection occurs if the temperature and duration of leaf wetness are conducive. This disease can cause substantial crop loss under the appropriate environmental conditions. (Refer to the "Spotts Chart," table 3 in IPM Disease Management Protocols, for infection requirements of black rot.) All green tissues of the vine are susceptible to infection. Leaves are susceptible for about one week after unfolding. See table 2 (69k pdf file) for varietal susceptibility to this disease.

Phomopsis Cane and Leaf Spot 277k pdf file
Black fruiting bodies (pycnidia) overwinter in infected canes and rachises. During early spring rains, spores ooze from fruiting bodies and are rain-splashed onto susceptible tissue. Shoot and leaf lesions appear within three to four weeks after infection. Diseased canes should be removed during pruning to reduce inoculum. Because inoculum remains viable in canes for several years, hedged vineyards are particularly at risk of incurring economic losses from Phomopsis, especially if rachis infections develop. Rachises are susceptible from the time they first become visible until after pea-size berries have formed. If a vineyard has a history of severe Phomopsis infections, a primary-season protectant disease management strategy (described at Immediate Prebloom and Primary-season Protectant Disease Management Strategy) should be used starting at three to six inches of shoot growth if wet weather is anticipated. See table 2 (69k pdf file) for varietal susceptibility to this disease.

Angular Leaf Scorch 224k pdf file
This disease is most likely to become evident when high rainfall occurs during the period of early shoot growth. Disease symptoms occur mainly on the leaves, appearing first as faint, chlorotic spots. Lesions enlarge and change from yellow to reddish brown, eventually killing the tissue. Lesions are confined by major veins and can have a yellow or red margin or no margin, depending on the cultivar. Infected leaves often fall prematurely. The fungus survives winter in infected leaves on vineyard floors. Cultural practices that increase air circulation can reduce the length of the leaf wetness period that favors disease development. See table 2 (69k pdf file) for varietal susceptibility to this disease.

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