West Michigan tree fruit update – June 27, 2017
Growers in west Michigan are settling into summer.
It is becoming easier to assess apple fruit crop load now that June drop has occurred. Apples are mostly in the 24 to 28 millimeter stage. Fruit set is extremely variable across the general Grand Rapids, Michigan, region. Sweet cherry harvest is beginning with really great fruit size reported.
Codling moth adult trap numbers are on the decline as first generation flight nears an end. We should be around 75 percent egg hatch and cover sprays continue to be very important and need to be maintained for at least another two weeks. A regional biofix was set for May 15 (250 growing degree-days base 50) and 634 growing-degree days base 50 (GDD50) have been accumulated.
Obliquebanded leafroller adults in traps are much declined as expected. A regional biofix was set for June 8 (1,017 GDD42) with 485 GDD accumulated since then. First egg hatch occurred in the last five to seven days and cover sprays are needed in difficult-to-manage blocks. Peak egg hatch is estimated for the end of the week. First visible larvae have not been found and are expected early next week.
San Jose scale is forming new waxy coatings and management will not be as effective. A regional biofix was set for May 21 (318 GDD50) with 555 GDD50 accumulated since then. There might be time to get management sprays targeting crawlers, but the window is closing quickly.
Second generation oriental fruit moth adult flight is increasing. A regional biofix was set for April 28 (307 GDD45) and 938 GDD have accumulated since then. We are in between generations of susceptible larvae. Cover sprays will again be needed the first week of July in all stone fruits and any apples with high pressure.
All stages of European red mites continue being found. Predator mites are also present. The threshold for June is 2.5 mites per leaf.
Dogwood borer adult flight continues but numbers are very low. Michigan State University Extension recommends monitoring burr knots for activity and traps for population potential and peak flight. Trunk sprays go on with peak adult flight, typically the first week of July.
No Japanese beetle adults were reported in the Grand Rapids area, but are expected to show up soon.