GRAPE IPM UPDATE

last updated August 8, 2008

Growing Degree Day (GDD) Accumulation (Aug. 8, 2008)

Above is the growing degree summary for six vineyards. I know that many of you are interested in the data so you can relate it to phenology and for estimating when harvest may take place this year. However, I emailed to the distribution list a link to sites that summarize growing degree days with the emergence of various insect pests. You can find the link to this information on the UCONN Grape IPM website. The reason I bring this up is one grower was following the GDDs and it accurately predicted the appearance of Japanese Beetles in his vineyard. This illustrates how you can use GDDs in your IPM program.

This is a tough year with high disease potential, but growers are doing a good job. Across Connecticut I see very little powdery mildew infection of the fruit. Black Rot is widespread and evident as leaf and fruit infections; however, in most cases the fruit infections are greatly limited. Verasion is just starting in early cultivars such as St Croix, Gewurztraminer, Foch, Pinot Gris, and others. Regarding the fruit, you should be scouting for Botrytis and other fruit rots. If you scout your vineyards now check the berries that have a pink-purple or unusual off-color for evidence of grape berry moth larvae--you will see a small hole with frass on the surface of the fruit around the hole. The affected fruit will be susceptible to fruit rot including Botrytis and the rot will then spread from the rotting berry. It is a good idea to go down several rows at various locations in your vineyard and use this as your indicator of prevalence of GBM in your vineyard. If the incidence is high you might want to consider a control strategy next year. My scouting this past weekend showed the highest incidence of fruit rots in cultivars that are in various stages of verasion.

Because it has been such a wet and overcast summer consider this report an alert for fruit rot diseases. This will only intensify as fruit ripen unless our weather pattern changes.

Richard Kiyomoto
Department of Plant Science
1376 Storrs Road Unit 4067
Storrs, CT 06269-4067
Telephone: (860) 429-0589 (Home)
Fax: (860) 486-0682
email: richard.kiyomoto@uconn.edu

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