West Michigan tree fruit update – July 25, 2017

After a short break, summer insects in apples will return.

Crop update

Sweet cherry harvest is complete and peach harvest is just beginning. Apples are between 1.5 and 2 inches in size. Rainfall has been minimal in the last week or so and irrigation systems are running as needed.

Insect update

Codling moth adults in traps are low with some catching a few in known high pressure blocks. A regional biofix was set for May 15, 2017 (250 GDD50) and 1,420 GDD base 50 have been accumulated. The Enviroweather codling moth model indicates we could be close to early egg hatch, but most traps in low pressure blocks have not increased to indicate the start of second generation flight.

Apple maggot adults started flying in sandy sites three weeks ago in very light numbers. We typically see a marked increase in apple maggot traps the last week of July. If we get significant rainfall (0.5 inch or more), we could see a flush of flight from the overwintering sites in the soil.

There has been a marked increase in apple maggot in the general Grand Rapids, Michigan, area over the last two or three years and all blocks should be trapping for it. Traps should be in place in known hot spots and along orchard edges near wooded areas with alternate hosts present. You only know what’s happening with apple maggot if you are trapping for it correctly. Red spheres with essence lures are the best for apple maggot.

Obliquebanded leafroller adult flight for the next generation could begin at any time. Michigan State University Extension advises changing lures in traps now to be sure you are capturing the start of flight. Larvae are in various sizes from third to fifth instar. A regional biofix was set for June 8, 2017, (1,017 GDD42) with 1,250 GDD accumulated since then.

We should be just past peak egg hatch for second generation oriental fruit moth and cover sprays are very important in tree fruits over threshold. This second generation of oriental fruit moth larvae could need to be managed in high pressure blocks for at least another 10 days. A regional biofix was set for April 28, 2017, (307 GDD45) with 1,625 GDD accumulated since then. Continue to monitor traps for adult activity and relative oriental fruit moth pressure. Scout for terminal collapse and fruit feeding.

Be on the lookout for tarnished plant bug activity in peaches. Pay attention to orchard edges, especially near mowed hay fields.

Japanese beetle adults continue to feed on various fruit crops and they show no signs of lessening. Continue to monitor and manage as needed.

Traps for spotted wing Drosophila have increased as expected and larvae can be found in tart and sweet cherry where management has ended.

All stages of European red mite continue to be found and overall red mites are very low in pressure this season. Predator mites are also present. The threshold for July is five mites per leaf.

Green apple aphids seemed to have collapsed or been killed in many apple blocks. Reports of woolly apple aphids continue.

Disease update

Hopefully, all apple blocks have had at least one fungicide already around the end of June for summer disease management in apples. Second applications should be considered again in the next week or two, particularly after the rains that might come this week, which will push us close to over 2 inches of rainfall since mid-June.

The pressure from summer disease is lower than last year so far, but don’t get behind early in managing this complex of diseases. 

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