Southwest Michigan fruit update – July 17, 2018

Dry conditions continue. This week will be cooler. Blueberry harvest continues as peach and plum harvest begins.

Desiree peach harvest started last week and other peaches are ripening now.
Desiree peach harvest started last week and other peaches are ripening now. All photos by William Shane, MSU Extension.


Last week was hot with highs near 90. No significant rain fell. Scattered storms crossed the region Saturday and Sunday. These storms dropped locally heavy rain, but most areas received less than a tenth of an inch. We have not had any wide spread significant rain in three or four weeks. Sandy soils are becoming very dry. Row crops are wilting in the mid-day heat. The evaporation rate is very high at 0.2 to 0.24 inches per day. The total water demand for July has been about three inches.

The dry conditions have really reduced plant disease activity. The passage of a cold front on Monday dropped temperatures and humidity, but little rain. Highs this week will be in the upper 70s. There is chance of thunderstorms on Friday and the weekend. Our heat accumulation is about a week to 10 days ahead of normal.

Southwest Michigan GDD Summary from March 1 through July 15, 2018


GDD 42 F

GDD 45 F

GDD 50 F

Benton Harbor (SWMRC)




Lawton (Lawton)




Fennville (TNRC)




Average for the SW region




Accumulation last week




Tree fruit

Spotted wing drosophila (SWD) numbers are up sharply. Previously most traps were catching only a few flies (less than 10). Now most traps are in the double digits. Growers with susceptible crops need to protect them. See the spotted wing Drosophila website for more information on SWD. Brown marmorated stink bug (BMSB) juveniles can be found. We expect them to mature into flying adults in late July.

Apricot harvest is winding down.

Peaches and nectarines are moving into early season variety harvest window. Estimated peach harvest dates are available on MSU’s Enviroweather. Redhaven harvest is projected to begin about August 1. Harvest of Earlystar and PF Early 8 Ball will start soon, with Harrow Diamond ready toward the end of this week in central Berrien County. Dry conditions has slowed brown rot activity. Fungicide treatments for brown rot are needed as fruit background color loses its green color. Leaf drop of older leaves due to bacterial spot infection earlier in the season is common for susceptible varieties. The second generation flight of Oriental fruit moth is underway and we are catching good numbers. Branch end flagging and fruit entries by first generation oriental fruit moth larvae are common at some sites.

In cherries, sweet and tart cherry harvest is ending. Defoliation caused by cherry leaf spot is common. Cherry leaves are always susceptible to cherry leaf spot infection and need to be protected. After harvest, growers should apply a long-lasting protectant fungicide to preserve the remaining leaves. Loss of too many leaves will weaken the tree affecting winter hardiness and reducing next year’s crop.

In plums, the harvest of Japanese plums has begun with Oushi Wase and Early Golden. Shiro harvest is expected later this week. Ripening fruit should be protected against apple maggot. We are catching apple maggot. Codling moth and oriental fruit moth also attack plums. SWD can be a problem in plums as they ripened. Plums become susceptible when they soften to approximately 3 lb. firmness, measured without skin, using a fruit firmness gauge fitted with a pear tip. Brown rot is a threat as fruit ripens.

In apples, both oriental fruit moth and codling moth are flying. This is the second flight of both these pests. Obliquebanded leafroller summer generation larvae have been actively feeding for several weeks and adults of the second generation should begin to emerge this week. Apple maggot adults have been flying for a month. This summer pest usually emerges following rains. The Trevor Nichols trapline in Fennville recorded a large surge in apple maggot numbers Monday. Most of Southwest Michigan has had enough leaf wetness for sooty blotch and fly speck development. Fungicides effective for these diseases should be included in cover sprays. Higher, exposed sites dry more quickly and have fewer wetting hours and less risk of these diseases.

Pears are growing rapidly. Pears become attractive to codling moth attack when they soften close to harvest in August. Pear psylla numbers are relatively low. Hand-pulling water sprouts will discourage psylla buildup.

Small fruit

Grapes are at berry touch and the clusters are closing. The hot, dry weather has slowed disease spread. We are still seeing a little black rot on the fruit but lambursca grapes (Concord & Niagara) will become resistant to fruit infection soon. Vinifera and hybrid grapes fruit should be protected for another month until veraison.

Growers should scout for powdery mildew and downy mildew on the leaves. Wine grape growers should include fungicides with good action against botrytis in fungicide sprays while they can still get sprays into the berry cluster. Otherwise wine grapes seem fairly clean.

The second grape berry moth flight is winding down. We are seeing a few grape berry moth stings. Now is a good time for growers and scouts to check their fruit to assess how well their sprays are holding up. Some growers with high pressure sites may require an additional insecticide application of a product with good contact activity. Larvae in the berries are protected from sprays and will form the third generation. It’s too early to tell if we will have a fourth generation of berry moth this year, but if the hot weather continues that will become more likely.

We have seen a large increase in Japanese beetles in some Berrien County vineyards. Growers with wine grapes or juice grapes with a light canopy, should check for beetle presence and leaf damage. They need to decide whether an insecticide is necessary. Typically juice grape canopies are very dense and can withstand heavy Japanese beetle feeding. Brown Marmorated stink bug nymphs, grape and potato leafhopper are scarce.

Niagara berry touch Black rot

This Niagara grape cluster is at berry touch and as the berries continue to expand the cluster will tighten. The brown berry was infected with black rot and will soon shrivel to a hard black mummy.

Blueberry harvest continues with both early and early mid-season varieties. Fruit ripens quickly in the heat and growers are struggling to keep up. We are seeing early ripening fruit on Jersey and other later ripening varieties. This ripe fruit is attractive to SWD. This fruit should be protected or harvested. Growers are applying fungicides and insecticides to protect ripening fruit against fruit rots and SWD. Many blueberry fields are very dry and need to be irrigated. Blueberries have a shallow roots and need frequent watering. In these hot conditions, blueberry fields need an inch of water every three or four days. See: Irrigating Michigan blueberries.

bluecrop 2ndpick (3)

Bluecrop harvest has begun in Southwest Michigan. Michigan will be harvesting large volumes of blueberries for the next month with an expected crop of about 100 million pounds in 2018.

Strawberry leaves are emerging after renovation. Growers should irrigate to get strong new growth. As new leaves emerge they should be protected from potato leafhopper which stunts strawberry growth.

Brambles harvest is underway. Both red and black summer raspberries are being picked. Most blackberries are still green. Japanese beetles are out. Target Japanese beetle as soon as you see it to prevent this pest from aggregating in your fields. Raspberries and blackberries are a preferred host for SWD and the fruit needs to be protected.

Cranberry bloom is ending. Green berries should be protected from fruit rots immediately after bloom.

Current berries are ripening and should be protected from SWD.

Upcoming meetings

  • There is a free two-day workshop on using drones in bush and tree fruit at the Southwest Michigan Research and Extension Center (SWMREC) on August 9-10. Space is limited, if you are interested in attending please register and answer the questions found here. Interested parties must sign up by July 25th. We will confirm your spot by August 1st. Please contact Erin Bunting ( for more information.
  • The Annual Trevor Nichols Research Center Field Day is Tuesday, September 25, 2018 from 1 to 4 p.m. at the Trevor Nichols Research Complex west of Fennville.

Related Articles:

Did you find this article useful?