A look at the Southwest Michigan fruit update

Michael Reinke, Mark Longstroth and William Shane

EAST LANSING, MI. – Sweet cherry harvest is underway. Other small fruits are harvesting in southern parts of the region.

Tree 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 last week and the previous week.

Apricots are 1.5 inches in diameter with hard pits. The crop is very good at some sites and poor at others. Dry conditions have not been very favorable for bacterial spot. Copper is about the only bactericide labeled for apricot, and most labels do not support post bloom use.

Peach and nectarine pits are hardening and fruit are starting to grow again. Early season varieties such as Rich May, PF1 and Harbinger are starting to develop red blush. Hand thinning is underway. Fruit susceptibility to bacterial spot decreases after pit hardening. Bacterial spot symptoms are still relatively rare. Fruit entries by oriental fruit moth are easier to find. Tarnished plant bug feeding on fruit is still ongoing.

In cherries, early season sweet cherries are being harvested. Tart cherries are red in Berrien County. Harvest should begin this week. Apply ethephon when fruit is in stage III of growth, when the least developed fruit turn straw colored. If ethephon is applied too early, the green fruit may stop growing and the stems stay attached resulting in the harvest of green cherries with attached stems. Since the early spring was so dry, cherry leaf spot symptoms are scarce for this time of year.

In plums, Japanese plums are at 30 millimeters. European plums are at 25 millimeters. June drop of green fruit continues. Crop prospects for plums look okay to only fair, depending on the site. Black knot control is still ongoing until terminal growth slows, generally at the end of June. Current warm wet conditions are conducive to bacterial spot infections.

Apple primary scab season is estimated to be over. 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. Codling moth, obliquebanded leafroller and oriental fruit moth flights and mating are continuing.

Small fruit

Grape bloom is ending. Labrusca and most hybrid grapes not impacted by the radiation freezes the first week of May are at buckshot to pea-size berries. There is still some scattered bloom on secondary shoots. Most vinifera cultivars are finishing or have finished bloom. May 25 through 27 can be used as general dates for wild grape bloom in southwest Michigan. There were several disease infection events with the weekend storms. Protectant fungicide sprays to control Phomopsis, black rot, downy mildew and powdery mildew are the management focus after bloom. Anthracnose was also recorded last week. Wine grape growers will also want to include botrytis in their disease management plans.

Blueberries have green fruit and beginning to show some blush. Some early varieties in southern Berrien County are beginning to show first blue color. Now that fruit is sizing, the crop is looking better. Disease control should focus on anthracnose infections to young green fruit, especially in irrigated fields. Shoot growth looks good. In fields without irrigation, the soils are extremely dry. Maintain irrigation to maintain shoot and fruit growth.

Cherry fruitworm and cranberry fruitworm egglaying is ending.

MSU 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 at

Strawberry harvest continues. The heavy rains over last weekend may cause an early end to harvest in some areas.

Bramble bloom is in various stages: Raspberry bloom has ended and blackberry bloom is ending. Fruit is sizing and coloring. Raspberry harvest has begun in Berrien County.

Miscellaneous crops

Hops growth is continuing. Side shoots are growing. Some flower buds can now be seen on the side arms.

Chestnuts are blooming.

Currant harvest is beginning.

Cranberries are blooming.