Southwest Michigan fruit update – June 29, 2021

Michael Reinke<reinkem3@msu.edu>, Mark Longstroth and William Shane<shane@msu.edu>, Michigan State University Extension - June 29, 2021

The region saw 3-6 inches of rain in the past week. Soils are saturated.

Apricots on a tree. — Several fruits are beginning to color up, meaning harvest is beginning or will begin soon. Cherries, blueberries, raspberries and currants are being harvested. Peach and apricot harvests will begin soon. Photo by Mike Reinke, MSU Extension.

Weather

Last week began cool with high temperatures near 70 following weekend rains. Temperatures increased to the high 70s or low 80s by Thursday, June 24. Storms moved across the area Thursday and continued through Saturday. Rainfall totals of 3-6 inches of rain were recorded across southwest Michigan. The heaviest amounts were along the Indiana border and counties on the northern edge of the region.

There are good chances of more rain the first half of this week. High temperatures for the week should be in the upper 70s. Lows will start in the mid-60s, dropping into the 50s with the drier air later in the week.

Soils are fairly saturated from all the rain in the last 10 days. This soil moisture has come at the right time. Plants are fully leafed out and July and August are when plants use the most water.

With the seasonal week, we picked up an average number of growing degree days (GDD) last week: 175 GDD base 42 and 120 GDD base 50.

Southwest Michigan GDD summary from March 1 - June 27, 2021
Station	GDD 42 F	GDD 45 F	GDD 50 F
Benton Harbor (SWMREC)	1686	1438	1078
Lawton (Lawton)	1707	1456	1085
Fennville (TNRC)	1505	1270	934
Average for the SW region	1661	1415	1055
Average last week	1486	1260	934

Tree fruit

Rain over the past two weeks initiated several recent disease infection events. The forecast for more showers this week could set up brown rot infections in stone fruit. San Jose scale males began showing up in the Trevor Nichols Research Center trapline on May 24. Crawler emergence is approximately 400 GDD base 51 F after biofix, which should be occurring in much of the region now. Japanese beetle has begun to emerge. We expect many insect pests to increase following the recent rains.

Apricot early varieties are starting to ripen, bringing increased susceptibility to brown rot. Apricot varieties have a range of bacterial spot resistance ranging from susceptible varieties such as Goldrich and Harogem to more resistant varieties such as Harojoy, Harlayne and Early Blush.

Peach and nectarine pits are hard with some fruit reaching 2.25 inches in diameter. Some fruits are showing a prominent tip this year. This is more typical of southern peaches and is due to hot weather in early fruit development. The early season variety Rich May is firm ripe at the Southwest Michigan Research and Extension Center. Flecking of fruit due to bacterial spot infections is showing on more susceptible varieties. Fruit entries by oriental fruit moth are easier to find. Tarnished plant bug feeding on fruit is still ongoing. Fruit turning from green to yellow/red have increased susceptibility to brown rot.

Spots on peach. — Bacterial spot is starting to show up on stone fruit. The flecking on this Rich May fruit and the spots on the leaf are common symptoms. Photo by Bill Shane, MSU Extension.

In cherries, sweet cherries are being harvested. Tart cherries are red in Berrien County. Harvest should begin within a week. Spotted wing Drosophila catches have been low but should increase soon. The low numbers are probably due to the hot dry spring. With the wet conditions of the last 10 days, we expect numbers to increase in the next week or two. Late harvested tart cherry blocks may need protection. Since the early spring was so dry, cherry leaf spot symptoms are scarce for this time of year, but recent rains have been very favorable for infection.

In plums, Japanese plums are at 30 millimeters. European plums are at 25 millimeters. June drop of green fruit is ending. Crop prospects for plums look OK to only fair, depending on the site. Black knot control continues until terminal growth slows, generally at the end of June. Bacterial spot infections are showing up on Japanese plum fruit.

Apple fruit size has been increasing rapidly. Summer NAA treatments to encourage return fruiting generally start about five weeks after full bloom, approximately in early June in central Berrien County. Fire blight symptoms are easier to find, but still relatively rare. Sufficient wetting has occurred to increase the risk of sooty blotch and flyspeck infection on fruit. The Fennville and Berrien Springs Enviroweather stations registered the most increase in wetting hours. Most sites in the area have enough hours of leaf wetness for this disease and growers should consider including fungicides in their cover sprays.

Codling moth, obliquebanded leafroller and oriental fruit moth flights and mating are continuing. Codling moth entries are becoming easier to see as the larvae get larger and push more frass out.

Holes in apple from codling moth feeding. — Codling moth damage is beginning to show up on apples. The frass near the calyx marks an entry hole. When this fruit was cut open, a third instar larva was feeding inside. Photo by Mike Reinke, MSU Extension.

Small fruit

Grape bloom has ended. For most grapes, bloom was compacted during the hot week around June 8. Labrusca and most hybrid grapes not impacted by the radiation freezes in May are at berry touch. Secondary shoots are near pea size berry. Most vinifera cultivars are near buckshot berry.

May 25-27 can be used as general dates for wild grape bloom in southwest Michigan. This is used for determining grape berry moth biofix. According to the grape berry moth model on Enviroweather, biofix for the second generation should begin between June 30 and July 3, depending on location. There were several disease infection events with the recent storms. Protectant fungicide sprays to control Phomopsis, black rot, downy mildew and powdery mildew are the management focus for the month after bloom. Anthracnose has also recently been found. Wine grape growers will also want to include botrytis in their disease management plans.

Blueberry harvest has begun. Some early varieties are around 10-25% blue fruit. With all this rain, disease control should focus on protecting green fruit from anthracnose. Water is standing in many fields making spraying difficult, and many growers are using aircraft to get their sprays on. Cherry fruitworm and cranberry fruitworm egglaying has ended. Spotted wing Drosophila numbers have been very low across the region. This is probably due to the hot dry conditions in May and early June. With cool wet weather and the ripening of wild berries such as bush honeysuckle and black raspberry, growers can expect to see increased numbers in a week or two.

Michigan State University is participating in a USDA-funded survey asking blueberry growers about their pollination practices. If you can, please take a few minutes to fill out the survey.

Blueberry bush. — Some blueberry varieties are beginning to show significant blue color. Some growers are starting selective hand picking of the earliest varieties. Photo by Mike Reinke, MSU Extension.

Strawberry harvest has ended for most growers. Renovation should begin as soon as you can work in the field.

Raspberry harvest has begun in Berrien County, with the harvest of both red and black raspberries. Blackberry bloom is ending. Fruit is sizing and coloring. Raspberries are very attractive to spotted wing Drosophila, and we expect number to increase in the next week.

Miscellaneous crops

Chestnut bloom is continuing.

Hazelnut bloom has begun.

Currant harvest is beginning.

Cranberry bloom continues.

Hand holding pawpaw fruit. — Pawpaws are continuing to increase in size. They are starting to plump up to reveal their final shape. These fruit will double in size before they are ready for harvest in September. Photo by Mike Reinke, MSU Extension.

Upcoming meetings

Viticulture Field Day will be returning to an in-person event this year. The event location is 12 Corners Winery on July 28, 2021. This will be an all-day event, beginning at 9 a.m. The traditional steak dinner and wine tasting will return. There will be limited attendance. Pre-registration is highly recommended.

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).