Southwest Michigan grape scouting report for July 25, 2017
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EmailDisease pressure is light. Grape berry moth egglaying is ending and SWD catch is up, which may be a problem after veraison.
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Growing degree-day (GDD) accumulations | |||
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Enviroweather station |
Wild grape bloom date |
GDD47 since wild grape bloom |
Estimated start of egglaying (1,620 GDD47) |
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May 26 |
1,359 |
mid-August |
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May 27 |
1,334 |
mid-August |
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May 27 |
1,349 |
mid-August |
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Disease
Disease development is light in the vineyards we scout. For example, in Niagara vineyards in Van Buren County, 2 percent of leaves were showing downy mildew lesions, and 1 percent of clusters showed black rot infection. Many of the hybrid grape sites we visited showed no visible disease symptoms. Continue to monitor for downy mildew and powdery mildew development on leaves. Treat with effective materials if sporulating lesions are seen and significant infection conditions occur.
Insects
Second generation grape berry moth egglaying is coming to an end, with zero to 12 moths per trap. Damage remains relatively low with only 2-10 percent of clusters showing stings and fewer clusters showing webbing or feeding along vineyard borders. No treatment is necessary until the beginning of third generation egglaying, which is still several weeks away.
No brown marmorated stink bugs have been trapped in vineyards. Damage from Japanese beetles, potato leafhoppers and grape leafhoppers is also low in the vineyards we scout. Scouting should continue for all of these pests as summer continues. Monitor for Japanese beetles especially in any plantings with meadows or grassy areas nearby. If treatment becomes necessary for Japanese beetles, Imidan, Sevin, Altacor, Avaunt, BeetleGONE and the pyrethroids are effective controls; of these, Avaunt, Altacor and BeetleGONE are considered reduced-risk materials.
We are catching more spotted wing Drosophila (SWD) in vineyards than in previous years. The catch has increased in the last two to three weeks. It is very likely SWD will be an issue in some vineyards this year after veraison. Michigan State University Extension advises hanging SWD traps in wine grapes.
As always, thanks for reading! Don’t be afraid to contact us at baughm30@msu.edu or masonk@msu.edu for questions, comments or suggestions. See you at the Viticulture Field Day on Wednesday.
