Hello everyone
I have a 5 year old concord grapevine in Westchester County NY that has been dealing with a long term infection of what I believe is Phomopsis. Over the first three years I thought nothing was wrong and that the numerous tiny brown spots on the shoots were just the new growth turning to wood, I even got some nice grapes in the third year. However in the fourth year the spots affected the rachises of the grapes and caused the bunches to fall off. This is when I realized something was wrong and learned about Phomopsis.
To try and fix things I got Mancozeb and mixed it according to the instructions for grapes, 3-4 teaspoons per gallon, though I only had a 32oz spray bottle so I just scaled it down and put 1 teaspoon in the bottle. Then I sprayed it directly on the plant at three times, once just before budbreak, once at around 5 inches of shoot growth, and once at about 10, all of these before bloom. In all three of these cases I sprayed about 24-48 hours before it was going to rain and the temperature was between 60 and 68 degrees, since I read these were the conditions when phompsis spreads best. During these sprays I did not use all 32 ounces of mixture, just enough to completely cover the plant.
I did not apply the fungicide any more times, however I realized I misread the bottle and in my area the maximum applications is 6 not 3. So I could have applied it more
Unfortunately I seem to have done something wrong since the Phomopsis came back this year, but I'm not exactly sure what. Please let me know what you think and if you have any other advice for dealing with this problem.
Thank you all for your help
