WSJM August 3, 2005 Grape Berry Moth – Part II
Last week I talked about grape berry moth. Today, I want to go into more detail with information taken from a Fruit CAT Alert article by Dr. Rufus Isaacs, MSU Extension Small Fruit Entomologist.
As I said last week, now is the time to scout. I was in a vineyard on Monday and found mature larvae. That means the next generation will be laying eggs by this time next week. In scouting, take a close look at grape clusters on the vineyard borders and also in the vineyard interior to determine how much cluster infestation is present. Sampling 25 clusters at two positions along the border and two from the inside is recommended. If one or two clusters in each 25 cluster sample has damage, you need to spray. Border and interior sampling will help you to determine if only a border spray is needed.
Achieving control of grape berry moth with any product requires good cluster coverage. The insecticide must get past the leaves to the clusters, and cover them, to be effective. Using 50 gallons of water per acre, driving more slowly, and spraying every row will all help to improve control. Pesticide longevity is also very important because egglaying by this generation is very spread out. Choose an effective insecticide with enough residual activity that both eggs and young larvae are controlled as they develop on the cluster. Short-acting products will be immediately effective but will leave the fruit at risk during the long period of egglaying if they are not reapplied. Finally, change the class of insecticide from whatever was used earlier in the season to help prevent grape berry moth from becoming insensitive to the currently effective tools that are available.
So, grape growers, get out and scout, use 50 gallons of water per acre, and spray both sides of every row to avoid having lost crop due to grape berry moth.
That is all for today. This has been Al Gaus for Michigan State University Extension in Berrien County.