August 31, 2015
The biggest influence on orchards and vineyards over the last 2-3 weeks has been the warmer temperatures and, at least north of Sturgeon Bay, the lack of disease causing rain events. Highs for the next week are forecast to be about 10 degrees above normal for this time of year. This will help apple and grape ripening.
Disease Pressure – Scab infections occurred on the 30th from Sturgeon Bay south, but not to the north where the last infection occurred between August 17- 19. As we approach harvest a final application of captan may be needed on fruit that is going into storage for any length of time.
Insect Pressure – Codling moth and apple maggot catches have been down in most orchards for the last 2 weeks. However, there are enough apple maggot still flying and laying eggs to warrant one more control application before harvest. Watch the label on whatever product that you choose to use for the pre-harvest interval. European red mite populations have been high in some orchards. The next week or two may be the last time that control applications will be worthwhile as cooler weather near harvest will naturally begin to reduce populations as they begin to get ready for the dormant season and lay overwintering eggs. Numerous miticides are available and should be applied at higher label rates as populations have a tendency to build quickly and can be much harder to knock down at this time of the season.
Disease Pressure – Infection events for cherry leaf spot have been fewer and farther between lately giving growers a break from the sprayer. Still post harvest fungicide applications have been extremely critical this season because of the numerous infection events and the high level of infected leaves seen throughout the season. Chlorothalonil containing products (Bravo, Echo Equus, etc.) are the best choice for post harvest control applications. Copper fungicides may also be considered where infected leaves were high and a second post harvest application is needed. It would be best to use the copper compounds in a second application 3-4 weeks after chlorolthalonil when temperature are not has warm to avoid phytotoxicity.
Insect Pressure – Cherry fruit fly and spotted wing drosophila (SWD) numbers have dropped off since harvest in many orchards. However, the level of SWD catches continue to increasing in some orchards, especially where there was an abundance of immature fruit left on the trees. Areas surrounding orchards with an abundance of honeysuckle also appear to be hosting higher populations as well.
Disease Pressure – The fewer rain events of late have resulted in a reduction of disease infection periods on grapes with the exception of powdery mildew. This disease can thrive without rain, developing on leaves during hot and humid weather. Many vineyards have seen an increase in leaf infections as well as some developing on the fruit.
Insect Pressure – Grape growers with a history of grape berry moth should scout carefully for the presence of eggs on berries and cluster stems as second generation grape berry moth are hatching.