Southwest Michigan fruit update — Sept. 5, 2017

Bill Shane<shane@msu.edu>, Mark Longstroth and Brad Baughman, Michigan State University Extension - September 05, 2017

Gala apple harvest continues. Grape harvest has begun. Growers need to be mindful of late season pests, which appear just before harvest.

Bins of picked apples are waiting in the shade to keep them cool for their trip to storage of the packing line. All photos by Mark Longstroth, MSU Extension.

Weather

Last week was cooler. Several cold fronts moved across the region dropping highs into the low 70s. Temperatures rose back to around 80 degree Fahrenheit over the next few days and then another cold front would drop the temperatures again. There were scattered showers with the passage of these cold fronts, but no widespread significant rain fell during the week.

Regional rainfall totals for the last two weeks averaged about 0.40 inches. Rainfall has been highly variable this year. Total rainfall in Southwest Michigan so far has averaged about 14 inches. Rainfall for the entire month of August ranged from 0.75 to about 3 inches of rain. The potential evapotranspiration for August was about 1 inch of water a week or 4 inches for the month. The season’s total demand since April 1 has been about 25.5 inches and the rainfall has been about 14 inches. Some areas are very dry and drought symptoms in unirrigated fields are common. Deep-rooted perennials do not seem to be suffering as much, but fall color change can be seen in stressed plants. This week will be cooler with highs dropping below 70 F into the 60s for most of the week. There is a chance of rain on Tuesday and Wednesday.

Southwest Michigan GDD Summary from Jan. 1 through Sept. 3, 2017
Station	GDD 42 F	GDD 45 F	GDD 50 F
Benton Harbor (SWMRC)	3676	3166	2390
Lawton (Lawton)	3511	3027	2288
Fennville (TNRC)	3329	2855	2137
Average for the SW region	3525	3036	2295
Ave from March 1	3425	2970	2262
Accumulation last week	144	123	91

Tree fruit

Brown marmorated stink bug adults can be found in many locations around the region, but trap catch numbers remain low except where catches have been ongoing since mid-July. We expect an upsurge in brown marmorated stinkbug feeding damage. Growers who suspect problems with stinkbugs should protect susceptible fruit such as late harvesting apples. Growers can review insect trap catches at Trevor Nichols Research Center. San Jose scale are causing red spots on fruit. Late September is typically the time that bucks will start rubbing their antlers on young fruit trees, especially trees close to woods. Growers depending on pheromone disruption for control of codling moth and oriental fruit moth, consider adding sprayable pheromones to keep protection strong up to harvest. Apply white latex paint to trunks of young trees to help prevent southwest damage caused by direct sunlight on trunks in winter.

Peach harvest continues primarily for direct market sales. Growers are harvesting with late varieties such as Autumnstar, PF-35, PF Legendary and Victoria. Fruit color and quality is good with dry weather enhancing sweetness. Oriental fruit moth trap catch numbers continue to be significant for some orchards. We should be at the end of the third generation oriental fruit moth flight. Suspected spotted wing Drosophila (SWD) larvae have been found in mature, apparently sound peach fruit. SWD could be a problem for peaches picked late for direct sales. Peaches with their fuzzy skin present a problem for SWD egg laying. Growers may want protection close to harvest, when they are late harvesting ripe peaches for direct sales of ripe fruit. SWD populations may be high due to nearby wild berry hosts. Stink bugs and tarnished plant bug damage increases fruit susceptibility to brown rot. As fruit colors, the need for brown rot protection increases. Growers should rotate fungicide classes used for brown rot control to avoid fungicide resistance problems. Borer sprays can be applied to trunks post-harvest and provide protection for the following several years.

In cherries, fall application of foliar nitrogen can help fruit size for next year. Defoliation from cherry leaf spot is the primary problem in some orchards, but many trees have at least half or more of their leaves remaining. Early defoliation reduces reserves for next season and reduces winter hardiness. Check trees showing water stress symptoms for American plum borer damage to the trunk at or slightly below the soil line.

Plum harvest continues with Damson, Italian, Simka, NY9 and Luisa. Flavor is generally good this year. Thicker-skinned European plums may be less favorable host for SWD than thin-skinned Japanese plums, but growers should still protect their fruit from SWD, especially when fruit is picked soft for direct sales. Ripening plums need to be protected from brown rot. Apple maggots also attackplums. SWD sprays should also control apple maggots.

In apples, fruit size is down in some sites due to the dry conditions. The effects of the May 8 freeze have been apparent for a while with a light crop in the bottom of the trees and larger fruit in the top of the trees. Harvests are quite low in these orchards due to spring freeze losses. McIntosh harvest has ended. Honeycrisp and Gala harvests are underway. Growers are harvesting smaller Empire and Jonathan apples for taffy apples. We are testing apple maturity using Irrigating is necessary in Michigan blueberries

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).