Southwest Michigan fruit regional report – July 21, 2015

Blueberry harvest hits full stride.

Peach fruit showing wart-like symptom of unknown cause. Photo by Bill Shane, MSU Extension
Peach fruit showing wart-like symptom of unknown cause. Photo by Bill Shane, MSU Extension


Last week was warmer. The week began with thunderstorms Monday morning, July 13, and the evening brought high winds and heavy rain to some areas. Mid-week was cool with high temperatures in the low 70s and lows temperatures in the 50s. The weekend was warm with highs near 90 and lows in the 70s. Strong storms crossed the region Saturday, July 18. Rainfall totals for the week ranged from less than an inch near Lake Michigan and over 2 inches further inland. The average was about 1.77 inches. Many soils are wet, but there are also some dry areas, and some growers are irrigating sandy soils. Evapotranspiration last week was relatively low (cool or warm cloudy conditions) with a weekly total of about 0.85 inches.

Weather for the upcoming week will be pleasant. Highs will be in the 80s and lows in the 60s. There will be a chance of thunderstorms over the weekend. With the warmer weather last week, we picked up about 29 growing degree days (GDD) base 42, 26 GDD base 45 and 29 base 50 per day. With a warmer week, we expect increased heat accumulations this week. We are about a week behind normal in heat accumulation and rainfall is about 2 inches above normal.

Southwest Michigan GDD summary from Jan. 1 through July 19, 2015


GDD 42 F

GDD 45 F

GDD 50 F

Benton Harbor (SWMRC)




Lawton (Lawton)




Fennville (TNRC)




Average for the region




Accumulation last week




Tree fruit

Soil moisture continues to be good with good growth. Foliar diseases are common in some orchards. The second generation of oriental fruit moth is flying. Tiny obliquebanded leafroller larvae of the second generation can be found webbing leaves and chewing holes in foliage. The Trevor Nichols Research Center reports catch of San Jose scale male adults after six weeks of zero catches. This is the start of the second generation, with first generation crawlers expected approximately 500 GDD51 from now or in about 20 days, depending on the temperature. Sprays for crawlers are timed about 650 GDD51

Apricot harvest has ended. Bacterial spot problems were relatively minor.

Peaches are growing rapidly. Split pits are common on some early-season peach varieties with light crops. Peach varieties being harvested now or shortly include Brightstar, Harrow Diamond and Risingstar. Bacterial spot continues to cause leaf and fruit spots, especially on susceptible varieties grown on sandy sites with low vigor. Mycoshield (21 day pre-harvest interval or PHI) can be used to help keep bacterial spot on foliage from spreading to fruit.

Oriental fruit moth trap catches are high in some orchards. Other direct fruit pests include tarnished plant bugs and common stink bugs, which cause pinhole punctures on fruit. Peachtree borer moths are still flying in area orchards and have the potential for egglaying in limb and trunk wounds. A few scattered cases of peach and nectarine fruit with wart-like bumps of unknown causes have been detected in Michigan, New York and Illinois. These symptoms have been seen in other years.

Sweet cherry harvest has ended. Cherry leaf spot symptoms are easy to find. Growers need to maintain protectant fungicide coverage before rain events. Late-harvested cherries that are soft-ripe on the tree may be prone to infestations by cherry fruit flies and spotted winged Drosophila (SWD) vinegar flies. Modest pruning can be done post-harvest on mature trees that have filled their space.

Tart cherry harvest has ended in southwest Michigan except for a few hand-harvested blocks and late, dark tart cherry varieties such as ‘Balaton.’ Crop yields and quality were very good. Cherry leaf spot is a significant problem in most orchards, in part due to heavy crops that made spray penetration into the canopy difficult. Growers can apply chlorothalonil after harvest to protect their remaining leaves. See “Controlling cherry leaf spot in orchards with existing symptoms” from Michigan State University Extension for more information. Growers using copper need to avoid copper building up on leaves to phytotoxic levels. Discontinue copper use when there is little or no rain between sprays.

Powdery mildew is becoming common in many orchards. There was a strong flight of greater peachtree borers and lesser peachtree borers. Treat with trunk sprays after harvest to prevent these pests. Like in sweet cherries, modest pruning can be done post-harvest on mature trees that have filled their space.

Berry harvester harvesting cherries
Harvesting high density tart cherries using a blueberry harvester. Photo by Mark Longstroth, MSU Extension

Japanese plum harvest of Methly, Shiro and Vibrant is underway. Apple maggots, oriental fruit moths, codling moths and obliquebanded leafrollers can infest fruit if not protected.

Apple estimated harvest dates are available from MSU Enviro-weather for weather stations across Michigan. Some of these dates include Sept. 8 for McIntosh and Sept. 30 for Red Delicious for central Berrien County. View a more detailed list of apple variety harvest dates for west central and southwest Michigan.

Apple maggot adults were caught this week at the Trevor Nichols Research Center. Mid-July is a typical emergence time for this insect, which is more common on sandy sites. Trapping with yellow sticky boards is a good method to determine if apple maggots are present. Growers need to include fungicides in some of their cover sprays to control sooty blotch and flyspeck. Growers should reapply fungicides for these two diseases whenever the hours of leaf wetness exceed 250 since the last fungicide application. Growers with a light crop or with bitter pit-susceptible varieties should include calcium in their cover sprays to reduce bitter pit. We are still catching codling moth and according to MSU Enviro-weather’s codling moth model, this is the second generation flight. Oriental fruit moth trap catches are high in some orchards. Growers should be scouting for obliquebanded leafroller larvae. Green aphids are increasing on active shoot growth.

Pear crop potential is good. Growers are removing watersprouts from trees to discourage pear psylla populations. Pear psylla numbers are increasing.

Small fruit

Japanese beetles are becoming more common. We are catching spotted wing Drosophila (SWD) in southwest Michigan. Many traps have not caught any flies, but a few more traps are beginning to catch flies. Yeast sugar traps appear to be catching more flies than some of the artificial lures. SWD is a pest of ripening fruit and numbers increase as wild berries ripen.

Grapes are at cluster tightening in Concord, Niagara and many hybrids. Clusters are still open in vinifera and other hybrid wine grapes. Juice grape berries are no longer susceptible to fruit infections of powdery mildew, downy mildew, black rot and Phomopsis. Vinifera grapes remain vulnerable to infection to these fungi. Wine grape growers should apply a Botrytis fungicide before bunch closure to reduce late-season fruit rots. See “Don’t let bunch rots ruin your grapes” for more information. Black rot fruit infections are developing in some vineyards.

Second generation grape berry moth egglaying continues. Growers using broad-spectrum contact insecticides should apply a second insecticide about two weeks after the first to control this generation. In wine grapes, scout for potato leafhoppers, which are in the area. Grape leafhoppers are scarce in juice grapes. Japanese beetles are feeding on leaves in some vineyards. Usually, only severe outbreaks of these insects require treatment.

Blueberry hand-harvest and machine harvest are underway. Bluecrop is the major variety being harvested now. Scouts are catching blueberry maggot flies and SWD. Ripening fruit needs to be protected from these pests. Growers should apply fungicides to protect fruit from anthracnose and alternaria fruit rots and new shoots from stem blights such as Phomopsis. Fields that were pruned hard last show more Phomopsis or winter injury than unpruned fields. Soil conditions are moist and irrigation is not necessary except at dry sites close to Lake Michigan.

Strawberry fields are putting out new leaves after renovation. Protect newly emerging leaves against strawberry foliar diseases and potato leafhoppers.

Raspberry harvest is underway for red and black raspberries. SWD and Japanese beetles are out and can be a problem in raspberries. Growers need to time their controls with harvest and pay close attention to the PHI on the pesticide label. Raspberries are also very attractive to SWD and growers should pay close attention to protecting against this pest.

Upcoming meetings

Be sure to register for the annual Viticulture Field Day July 29 from 9 a.m. to 6 p.m. at the Southwest Michigan Research and Extension Center1791 Hillandale Rd., Benton Harbor, MI 49022. Grape growers, winemakers and others interested in viticulture are invited to attend. This is a full day of viticulture. The event includes an outdoor trade show, equipment demonstrations and tours of the research farm. Follow the link above to learn more about the event and register for this annual open house focused on grape production in southwest Michigan. For more information, contact Diane Miner at

See also

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