West central Michigan tree fruit update – June 27, 2017

Dave Jones, Michigan State University Extension - June 27, 2017

Updates on cherry leaf spot, apple scab, spotted wing Drosophila and oriental fruit moth.

Peach shoot damage and fruit ooze from oriental fruit moth damage in New Era, Michigan, on June 25. Photo by Dave Jones, MSU Extension.

Weather update

Sporadic rains over the past several days throughout west central Michigan have presented challenges to growers trying to stay on top of spray management programs. Frequent rains combined with afternoon sunshine has resulted in rapid sizing, particularly in the cherry crop.

More intermittent rain in the forecast for the next several days will likely continue to cause issues with spray coverage and timing, leading to heightened concerns over insects and disease.

Growing degree-days (GGD) since Jan. 1 for west central Michigan
MSU Enviroweather Station	GGD Base 42 current	GGD 45 current	GGD base 50 current
Benona / Shelby	1155	923	600
Elbridge / Hart	1342	1100	756
Fremont	1458	1206	846
Hart	1341	1096	752
Ludington	1297	1059	720

Crop update

Sweet cherry harvest has started for early cultivars like Cavalier. Quite a bit of fruit crack has been observed this year as heavy rains have continued through fruit development. The moisture has also resulted in noticeable brown rot, particularly in the canopies of older, larger sweet cherry trees.

Tart cherry harvest will be starting late next week in early blocks in the region. Growers are applying Ethephon in coming days to help loosen fruits. Cherry leaf spot continues to be a concern, as most blocks in the region have at least a small amount of the disease. Many blocks have been heavily affected at this time, yellowed leaves can easily be seen dropping off of damaged trees at these sites.

No spotted wing Drosophila (SWD) larvae have been detected in cherry fruits yet, but adult trap catches have jumped considerably in recent weeks. All 10 sites in the west central region have had sustained catches for the past three weeks and populations are starting to show signs of rapid increase. Growers are actively managing for spotted wing Drosophila every seven days at this time.

Apple fruit is sizing rapidly. It is a lighter crop but generally looking good in most sites. Apple scab and fire blight have been low this season in most blocks. Primary apple scab ended early last week, but growers with active scab lesions in apple blocks from infections that occurred during primary scab continue to apply cover sprays ahead of rain to prevent damage on fruits.

No brown marmorated stink bugs have been caught in any of the traps in the. Codling moth sprays will continue to be applied until mid-July, but trap catch numbers have been lower overall, particularly in blocks with mating disruption.

Peaches are sizing rapidly throughout the region. Growers in many places were surprised this week by heavy edge damage from the larvae laid by the first generation of oriental fruit moth. Michigan State University Extension entomologist Larry Gut and I wrote an article, “Management considerations for peach orchards with edge damage from oriental fruit moth,” addressing questions about this situation and necessary action related to this edge damage as this issue leads to a lot of confusion about the role of mating disruption in oriental fruit moth management.

Growers who are experiencing heavy edge damage are encouraged to read this article and select an application from the included table that excludes the pyrethroid insecticides due to concerns of resistance.

This article was published by Michigan State University Extension. For more information, visit https://extension.msu.edu. To have a digest of information delivered straight to your email inbox, visit https://extension.msu.edu/newsletters. To contact an expert in your area, visit https://extension.msu.edu/experts, or call 888-MSUE4MI (888-678-3464).