10- to 12-inch Shoot Growth
IPM practices to be implemented
- start Postinfection Disease Management Protocol for varieties with low susceptibility to powdery mildew, moderate to low susceptibility to black rot, and no severe disease problems the previous year, see discussion below.
- continue disease management protocols started previously
see discussion below.
- weather parameters of temperature, precipitation, and leaf wetness
- Eutypa Dieback
- Banded Grape Bug
Inoculum available for infection
see discussion below.
- powdery mildew 490k pdf file
- black rot 548k pdf file
- Phomopsis Cane and Leaf Spot 277k pdf file
- downy mildew 300k pdf file
Continue to monitor weather conditions for infection periods. Vineyards with low susceptibility to powdery mildew and black rot should now be using this protocol. For example, Concord vineyards with no history of powdery mildew and/or black rot outbreaks have successfully used the postinfection protocol starting at the 10-inch shoot growth stage. Consult IPM Disease Management Protocols for details on fungicides and timings used with this protocol.
One disadvantage of the postinfection program is that there are no postinfection fungicides that will manage Phomopsis Cane and Leaf Spot or downy mildew, and protectant applications for them are not a part of the protocol. While low levels of Phomopsis and downy mildew are managed using this protocol, the primary-season protectant disease management strategy described in the next paragraph and on page 39 should be used for vineyards with a history of severe Phomopsis or downy mildew infections.
Primary-Season Protectant Disease Management Protocol
This protocol can be used in place of the postinfection disease management protocol for varieties that are highly susceptible to black rot, Phomopsis Cane and Leaf Spot, and/or downy mildew, such as Concord. Both the postinfection and the protectant disease protocols attempt to greatly reduce the amount of primary infections through early-season fungicide applications, but a different schedule is used for each. This protocol uses a protectant schedule and will result in four fungicide applications being made each year. Consult Primary-Season Protectant Disease Management Protocol for specifics on the fungicides and timings to be used.
This protocol does not provide management of powdery mildew prior to the prebloom application. Therefore, it should not be used in vineyards with a history of powdery mildew infections or in vineyards with highly susceptible varieties. See table 2 (69k pdf file) for varietal susceptibility to this disease.
Eutypa Dieback, 311k pdf file
Eutypa dieback is a fungal disease appearing as cankers on trunks and arms of infected grapevines. New shoots above cankers appear stunted, with shortened internodes and small, cupped, greenish yellow leaves. Healthy growth may overgrow affected shoots by midsummer. Infected arms or trunks should be removed in late spring, when foliar symptoms are noticeable and wounds are less susceptible. Pruning should be far enough below the canker that healthy wood is evident and all infected wood is removed. Because Eutypa moves slowly through a vine, reinfection can be reduced by double cutting. After early-season removal of diseased wood, complete removal of the trunk or cordon in midsummer can reduce the number of reinfection sites. Any infected wood or stumps should be removed from vineyards and burned. See table 2 (69k pdf file) for varietal susceptibility to this disease.
Banded Grape Bug
Nymphs (the immature stage) of this bug feed on grape clusters during the prebloom period and may sporadically reach high enough densities to be a concern. They are most common along vineyard edges near wooded areas. Monitor nymph populations on 25 or more grape clusters from both the edge and interior of the vineyard. Nymphs are found on the clusters and can be distinguished from other bugs by their black-and-white-banded antennae. More than five nymphs per cluster may cause economic damage, although these densities are rarely reached.
Mildew 300k pdf file
Rainfall is the most important environmental factor promoting downy mildew epidemics. Infected leaves on vineyard floors harbor overwintering structures (oospores). In spring, if water is present and temperatures are at least 50°F, oospores germinate and release swimming spores (zoospores) into freestanding water. Zoospores are rain splashed onto susceptible leaves and clusters, and cause infection. Secondary sporulation occurs at night, at temperatures above 55°F and relative humidity above 95 percent, on the undersides of infected leaves. These spores are spread by air currents or rain splashed onto susceptible tissue, and additional zoospores are released if a film of water is present, initiating secondary infections. This cycle can repeat throughout the summer whenever weather conditions are favorable. Management of downy mildew with properly timed, protectant fungicides is currently the only reliable method of management. The immediate prebloom through immediate postbloom period is the most important time for managing primary infections of downy mildew and thus minimizing secondary spread throughout the summer.