August 18, 2017
Through the rest of the growing season, this pest update will be renewed every two weeks.
Rain, rain and more rain! I’m getting sick of spraying! Again of multiple infection periods for apple scab and cherry leafspot. Post-harvest fungicide applications continue to be applied on cherry in the hope of maintaining as many leaves on the trees for as long as we can. With the amount of inoculum present and still a month and a half to the first official day of fall, growers may need to consider a second post-harvest application to maintain healthy leaves for the next month or two.
INSECT & DISEASE CONTROL
Disease Pressure – Fungicide application can now be reduce as we approach harvest. Most orchards can get by with one more application. The exception to this is where growers still have heavy leaf scab present. They should continue to apply protectant fungicides on a 10-14 day schedule right up through PHI.
Insect Pressure – A final application for 2nd generation codling moth and apple maggot should be made between now and early September. Good to excellent rated materials for both of these pests should applied. These include Imidan, Assail, Exirel, Delegate, Voliam Xpress and Voliam flexi.
It may be to late to make control for European red mites. Fortunately very low mite levels have been the case in most scouted orchards.
Disease Pressure – Leaf spot levels continue to drop compared to earlier in the season. Post-harvest fungicide applications (meaning more than the tradition one application) are critical due to 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 temperatures are not has warm to avoid phytotoxicity.
Insect Pressure – Populations of SWD have increased to record trap catch numbers in post-harvest orchards. However, there is no advantage to making control applications at this time. In fact, any controls applied now would likely speed up the development of resistance. The presence of high populations, with the short generation times occurring now, will expose larger numbers of individuals to any materials applied resulting in greater selection pressure and a greater probability of resistant population development.
Click on links below for two very good articles on SWD:
Links to individual Enviro-Weather stations: