Grand Rapids, Mich., area tree fruit regional report – Aug. 22, 2013

Consider late season apple pests related to your harvest dates.

As we are nearing the beginning of harvest for early apple varieties, Michigan State University Extension advises growers to take some time to double-check the pre-harvest intervals (PHIs) for any late season pesticides that might be needed for various insect pests.


Second generation codling moth adult flight is underway and early egg hatch should be occurring. A second generation regional biofix date of July 25 was set and there have been 400 GDD base 50 accumulated since then. This indicates roughly 25 percent egg hatch for codling moth and the need to keep good cover sprays on in blocks over threshold is crucial right now and for the next several weeks. A third generation of codling moth is not expected for 2013.

Obliquebanded leafroller adult flight for the overwintering generation should be coming to an end and there are a few small larvae present now, but they are very low in numbers overall. Continue to monitor for obliquebanded leafroller larvae for the next few weeks. We typically do not apply control measures for this overwintering generation, but if you are seeing obliquebanded leafroller larvae and need to do follow-up codling moth sprays, choose an insecticide with activity for both if you can.

Variable trap numbers of apple maggot adults continue to be reported. Overall, apple maggot numbers are low this year. Some areas to the north received a half-inch to even an inch and a half last night (Aug. 21) and this could bring out a few more apple maggots from their soil hibernation areas. Having clean traps in apple blocks is still important.

All stages of European red mites are present. Beneficials are present. At this late time in the growing season, it is probably not economically feasible to spray for mites any longer. The exception would be in blocks of late harvested varieties with very high mite per leaf numbers and dry soil conditions.

Oriental fruit moth third generation flight has begun and in about a week, cover sprays will again be key in stone fruits. A regional biofix was set for May 15 (337 GDD45) – GDD since biofix = 2,078. Be sure to check PHIs for late harvested peaches and plums. Third generation oriental fruit moth larvae have been known to feed on apples if blocks are near stone fruits or possibly in apple blocks that have been under mating disruption for many years. The only way to know for sure is to have a trap or two up in these scenarios.

Invasive species

The number of spotted wing Drosophila trapped across Michigan continues to increase and is causing issues in soft fruits such as raspberries and blueberries. A few brown marmorated stink bugs have been trapped from known hotspots in more southern areas of the state. No brown marmorated stink bugs have been trapped from any commercial production systems in Michigan at this time.


Continue to protect for brown rot in stone fruits as they near ripening. The very hot and humid weather this week will get it started and even more hot and humid weather is in the forecast for next week.

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