Southwest Michigan fruit update — Aug. 22, 2017

Growers are harvesting peaches, plums, pears and early apples.

Zestar is a new early apple being harvested now. All photos by Mark Longstroth, MSU Extension.
Zestar is a new early apple being harvested now. All photos by Mark Longstroth, MSU Extension.

Weather

Last week was warm. High temperatures were in the 80s and lows near 60. Scattered showers brought rain last Tuesday morning, Aug. 15, and this Tuesday, Aug. 22. Rainfall totals have been very variable this year, with intense rain in some areas and much less in others. Total rainfall for the week was about a half-inch, but amounts varied from 0.3 to 1.3 inches of rain. Last week’s showers temporarily reduced the drought stress in some areas.

Last week’s potential evapotranspiration was about 1 inch of water, where it was available. The season’s total demand since April 1 has been almost 23.5 inches and the season’s rain across Southwest Michigan averages of almost 13.5 inches. Some areas are very dry and drought symptoms in unirrigated woods and fields are common. Leaves coloring and falling is common.

This week began hot with highs near 90. It will be cooler with highs in the low 70s. There is little chance of showers after Tuesday until next week. We continue to be about a week ahead of normal, but with the actual crop harvests, about two weeks ahead of normal.

Southwest Michigan GDD summary from Jan. 1 – Aug. 20, 2017

Station

GDD 42 F

GDD 45 F

GDD 50 F

Benton Harbor (SWMRC)

3,362

2,893

2,185

Lawton (Lawton)

3,207

2,763

2,097

Fennville (TNRC)

3,029

2,598

1,946

Average for the SW region

3,223

2,775

2,100

Ave from March 1

3,127

2,709

2,067

Accumulation last week

206

185

150

Tree fruit

Japanese beetle numbers are low. Brown marmorated stink bug trap catch numbers have been low except in a few sites where catches have been ongoing since mid-July. We expect an upsurge in brown marmorated stink bug feeding damage soon in mid- to late August. Growers can review insect trap catches at Trevor Nichols Research Center. San Jose scale red marks on fruit are showing up from the third generation of crawlers.

Peach harvest continues to move rapidly. Growers are harvesting the Cresthaven group, including PF24C, Messina, Glowingstar and Gloria. Fruit color and quality are good. Fruit size is good where thinning was done early.

Brown rot is the primary problem in some orchards. Fruit speckles due to bacterial spot can be seen where infected leaves are nearby. Peaches continue to shed older leaves. Some of these are the basal leaves with no discernable disease symptoms. To increase fruit color, lightly summer prune one to two weeks before harvest on varieties needing more color.

Oriental fruit moth trap catch numbers are generally up and are significant in some orchards. We are in the third generation oriental fruit moth flight. Stink bug and tarnished plant bug damage increases fruit susceptibility to brown rot. As fruit colors, the need for brown rot protection increases. Rotate fungicide classes used for brown rot control to avoid fungicide resistance problems.

In cherries, defoliation from cherry leaf spot is a serious problem in some orchards. Other stresses such as drought can cause leaf drop as the stressed trees shut down. This reduces reserves from next season and reduces winter hardiness.

Plum harvest continues with NY6, Early Italian and some early picking of Stanley. Thicker-skinned European plums may be a less favorable host for SWD than thin-skinned Japanese plums, but protect all fruit from spotted wing Drosophila (SWD), especially where fruit is picked relatively soft for direct sales.

Ripening plums should be protected from brown rot. Apple maggot also attacks plums. SWD sprays should also control apple maggot.

In apple, Zestar, Ginger Gold and Paula Red harvest continues. We are testing apple maturity using Irrigating is necessary in Michigan blueberries


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