West Michigan tree fruit regional report – June 21, 2016

Don’t let your guard down during the dog days of summer.

Weather and growth stages

All tree fruits have been sizing quickly with the warmer than normal weather that has settled in recently.

Apples have set up nicely with what is seeming to be an average-sized crop. Fruit size should be very good this year due to many sites having a king bloom crop on the tree. Predicted harvest dates for apples are now available on the Michigan State University Enviro-weather website in the fruit tools section. At this time, harvest dates appear to be very similar to the 2015 season.

Peaches continue to grow fast with hand-thinning continuing. The crop in the general Grand Rapids, Michigan, area appears to be set very well.

Sweet cherries are showing red color with some early varieties ready for harvest soon. The majority of harvest on the Ridge will be in a couple of weeks. There seems to be a higher bird pressure this season in cherries.

Growing degree-day (GDD) totals for the Sparta Enviro-weather station are 1,365 GDD base 42, 1,070 GDD base 45 and 802 GDD base 50. On average, degree-day totals put this area eight days ahead of normal average accumulations.


Growers and scouts should continue to be on the lookout for primary apple scab infections as fruits and leaves are still susceptible to secondary infections. Once leaves and fruit toughen up in the summer months (July and August), further scab infections should be reduced in blocks with active infections.

Fire blight continues to be reported in low pressure here and there on the Ridge – some is from blossom blight infections and some is shoot blight or perhaps trauma blight. In the Hart, Michiga, area and areas to the north, more blight is being reported due to blossom blight. As long as trees are still actively growing, fire blight can progress. If you have active blight in blocks, keep on it with cover sprays as needed until terminal bud set. I suspect this year’s blight infections might get a little worse before it settles down in July and August. Be ready to cover up for stormy conditions that tear up foliage, which can further spread fire blight.


Codling moth adult flight continues and seems to be declining with well over 50 percent of moths emerged. Egg hatch should be around the 50 percent mark in most blocks. A Grand Rapids, Michigan, regional biofix was set for May 23 (302 GDD50) and 500 GDD50 have accumulated since that date. You can track degree-days for your own biofix date in the Enviro-weather codling moth model. Cover sprays are crucial now and need to be reapplied as rain warrants.

All stages of European red mite are found in commercial apple blocks. Continue to monitor more closely as petal fall timed miticides might begin to break soon.

Adult flight of obliquebanded leafroller should be nearing a peak level, but eggs are not yet hatching. A Grand Rapids, Michigan, regional biofix was set for June 12 (1,132 GDD42) and 225 GDD42 have been accumulated since that date. Early egg hatch is predicted for June 26 – the target for high pressure blocks. Peak egg hatch is estimated for around July 3. Low pressure blocks can scout for larvae and spray accordingly.

Crawlers of San Jose scale found last week are now settling down to form their waxy coatings. Cover sprays might not be as effective if done now and might be better saved to target the second generation.

Second generation of oriental fruit moth flight is underway with adult number increasing each week. A regional biofix was set for May 6. Approximately 308 GDD45 and 840 GDD45 have been added since then. The Enviro-weather oriental fruit moth model indicates second generation larvae will be at 10 percent hatch around July 3 or 4 and that’s the time to target them again in stone fruits and perhaps apples with very high trap numbers (greater than 60 per trap per week).

Various species of aphids can be found in all tree fruits, and numbers seem to be building now each week. There are syrphid fly larvae and lady bug larvae present in some populations. MSU Extension advises growers to continue monitoring for all aphid species in all tree fruits as well as the beneficials that attack them.

Dogwood borer adult flight is beginning. Target trunks at peak adult flight – typically the first week of July in the Grand Rapids, Michigan, area.

Adult flight of spotted wing Drosophila continues in low numbers and mainly in strawberry sites. None have been reported in sweet cherries yet.

No reports of brown marmorated stink bug egg hatch or nymphs in the Grand Rapids, Michigan, area. Reports from urban homeowners of an increase in overwintering adults in homes are becoming more and more common each year.

Japanese beetles should begin emerging from overwintering soil sites soon, particularly around the Grand Rapids, Michigan, area where higher amount of rainfall have been recorded in the last few weeks. 

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