Southwest Michigan fruit update – Sept. 4, 2018

William Shane<shane@msu.edu>, Mark Longstroth<$author.email> - September 04, 2018

Tree fruit harvest continues. Grape harvest will begin soon.

Brown marmorated stink bug on peach leaves. Photo by Bill Shane, MSU Extension.

Weather

Last week was warm and wet. The last weekend in August was muggy with humid conditions and highs near 90. The passage of a cold front brought heavy rains and strong winds. Mid-week was cooler with highs just below 80. Thunderstorms moved through the area during the Labor Day weekend, bringing more wind and rain and high temperatures near 90. These temperatures are much warmer than the normal range for August and September.

Storms across the region dropped 2.5 to 5 inches of rain for the week. The season-long total for the region is about 25 inches; a lot of rain and some fields have been wet all season. The warm and humid conditions will last for a few more days this week. A cold front will move south on Tuesday and Wednesday, Sept. 4 and 5, bringing cooler temperatures and some more rain.

Weather for the upcoming week should be cooler by mid-week with highs in the 70s. The remnants of tropical storm Gordon may cross the region next weekend. The long-term outlook for the fall is for warmer than normal conditions, but there is no prediction as to whether we will have more or less rain than normal. Normally September is one of our most active weather months.

Southwest Michigan GDD summary from March 1 – Sept. 3, 2018
Station	GDD 42 F	GDD 45 F	GDD 50 F
Benton Harbor (SWMRC)	3,597	3,181	2,514
Lawton (Lawton)	3,613	3,181	2,515
Fennville (TNRC)	3,450	3,041	2,390
Average for the SW region	3,601	3,184	2,514
Accumulation last week	246	222	182

Tree fruit

San Jose scale trap catches continue to decline. We are seeing red spots on apples and peaches due to scale in sites with high scale populations. Apple maggot trap numbers continue to decline. Brown marmorated stink bug (BMSB) adults are showing up in more sites. A few hot spots with BMSB damage are being reported for peach and apple orchards close to woods and soybeans. Some adult BMSB are being seen on buildings, but appreciable aggregating for fall has not started yet. Spotted wing Drosophila (SWD) numbers continue to be high.

Peach and nectarine varieties being harvested now include PF23, Flameprince, PF27A and Autumnstar. Peach scab and brown rot are easy to find on fruit of susceptible varieties with weak fungicide programs. Problems due to oriental fruit moth in fruit are relatively rare this year, perhaps due to increased use of pheromone disruption in the region. Brown marmorated stink bug damage is being found in peaches. Symptoms include white to brown regions of slightly firmer, disorganized peach flesh close to the skin.

Peach inking symptoms (brown to bronze patches) are showing up on fruit after sorting and refrigerated storage. Peach varieties with highly red colored blush tend to be more prone to inking. Other factors favoring inking include abrasions during harvesting and sorting, low and high pH water in dump tanks, fungicides such as captan close to harvest, dusty hot weather, rain and spray applications.

Inking on Peach

Peach inking causes dark spots on the fruit. Almost any injury can cause this superficial injury. Photo by Bill Shane, MSU Extension.

Cherry defoliation by cherry leaf spot is very common. Maintain fungicide protection to preserve the remaining leaves.

Plum harvest of Castleton, Long John and Fortune are finishing up, with Stanley and Luisa underway. Brown rot has been the primary concern. Protect ripening plums against apple maggot. Apple maggot numbers are declining in Trevor Nichols Research Center trap line. Codling moth and oriental fruit moth can also attack plums. SWD can attack plums as they ripen. Plums become susceptible when they soften.

Apple predicted harvest dates for Gala and Honeycrisp for central Berrien County are Sept. 10 and 18, respectively. Apple maturity test reports from Michigan State University Extension are available Wednesdays from now until mid-October for the major apple growing regions in Michigan.

Growers with a light crop or with bitter pit-susceptible varieties should include calcium in their cover sprays to reduce bitter pit. Yellow leaves and leaf drop are common in Golden Delicious due to necrotic leaf blotch. This is a non-pathogenic, physiological problem that shows up during hot spells with rain.

necrotic leaf blotch

Necrotic leaf blotch occurs in Golden Delicious and other varieties, often after periods of hot and dry weather followed by rain. Photo by Mark Longstroth, MSU Extension.

In orchards where apple scab is present on fruit and leaves, consider beefing up fungicide coverage shortly before harvest to help prevent pinpoint scab showing up in storage. Reapply fungicides for sooty blotch and fly speck whenever the hours of leaf wetness exceed 250 hours, or 2 inches of rain have occurred since the last fungicide application. Most of the region received over 2 inches several times this last week.

Black rot, frogeye leafspot and rust leaf spot symptoms are common in apple plantings where fungicide protection is inadequate. Salmon-colored spores of bitter rot can be found on apple fruit rot spots. Light-colored fruit such as Honeycrisp and Empire are more susceptible than darker varieties.

Scout for populations of European red mite that may lay eggs in the calyx of the fruit and treat hot spots with a miticide. Catches of oriental fruit moth and codling moth have risen in many orchards. Obliquebanded leafroller are laying eggs. Apple maggot trap catch numbers are generally low after a strong flight earlier in August.

Pear harvest of the Bartlett variety for local sales is still underway. Blake’s Pride and Gem in also being harvested. Harrow Sweet harvest will start soon. The primary insect threats now are codling moth and brown marmorated stink bug.

Small fruit

Grapes have finished veraison. Berries are soft, well-colored and are now accumulating sugar. Some table grapes are being harvest for the local markets. Niagara harvest for juice will start in another week or two. Rains reduce sugar accumulation by increasing berry size and diluting the juice.

We are seeing more downy mildew on the leaves. At this time the fruit are resistant, but downy mildew becomes a serious problem in fall when we have heavy morning dews and lots of free water. Protect susceptible varieties to preserve the leaves and ripen the grapes. Botrytis and sour rot symptoms are apparent in damaged wine grape clusters. With the warm, wet conditions, protect your wine grape crop from botrytis.

Fourth generation grape berry moth are now flying. The third and fourth generation are overlapping and you can expect the berry moth numbers to increase. We are seeing active feeding, especially along the wooded vineyard edges. Check vineyards and consider controls of the fourth generation. Insecticides with good contact activity and a short pre-harvest interval are the best option.

The number of spotted wing Drosophila (SWD) flies keeps increasing. We are seeing SWD and other vinegar flies in clusters with split or damaged berries. Be mindful of SWD and vinegar fly infestation as harvest nears and more split berries occur.

We seeing brown marmorated stink bug (BMSB) in vineyards, but no signs of feeding. Look out for this insect until harvest. See “Brown marmorated stink bug increasing in grapes” from MSU Extension for more information.

Blueberry harvest is over. Many growers had a light crop. Two factors probably contributed to the short crop. One was the bitter cold around New Year’s, which caused some winter injury. Bloom in general looked good and began about May 15. The second factor was weather during bloom was very wet and rainy with few good days for pollination. This wet weather was followed by alternating cool and wet and very hot and dry weather—not the best conditions for early fruit development. No doubt these poor conditions during and after bloom contributed to the light crop in later season varieties.

With the heavy rains last week, relax your irrigation. Maintain bush health to set a good crop of flower buds for next year. Some growers are pruning while labor is available.

Strawberries are putting out good growth and new runners. Fields should be protected from leaf diseases and potato leafhopper, which stunt plant growth. Maintain irrigation to assure good yields next year. As the day length shortens, the plants will set flower buds for next year. Day neutral berries are blooming again and fruit is being harvested. Protect ripening strawberry fruit from SWD and harvest as frequently possible to minimize the amount of time the fruit is available to the fly.

Bramble harvest continues with fall raspberries. Raspberry are a preferred host for SWD and the fruit always needs to be protected.

Upcoming meetings

The Annual Trevor Nichols Research Center Field Day is Tuesday, Sept. 25, 2018, from 1 to 4 p.m. at the Trevor Nichols Research Center west of Fennville, Michigan.

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).