Southwest Michigan fruit regional report – August 25, 2015

Peach harvest has passed the peak. Apple season is cranking up as more varieties are being harvested.

Shallow feeding damage to peach fruit by obliquebanded leafroller larvae. Photo by Bill Shane, MSU Extension
Shallow feeding damage to peach fruit by obliquebanded leafroller larvae. Photo by Bill Shane, MSU Extension


Last week was warm to hot with high temperatures in the mid-80s to mid-90s and lows temperatures in the 50s and 60s. Several rains during the week delivered 0.75 to 2.5 inches of rain, which helped relieve dry soils.

Southwest Michigan GDD summary from March 1 through Aug. 23, 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

Oriental fruit moth larvae from current generation are various sizes, up to 0.667 inches in length, with increased trap catch signaling the start of the third generation flight. Obliquebanded leafroller adult flight of the second generation has increased with the recent warm weather. Larvae from the second generation can be a threat until they reach the third instar in late August to early September. San Jose scale crawlers are expected approximately 500 GDD51 from the July 20 biofix based on the Trevor Nichols Research Center (TNRC) traps. Sprays to control crawlers are timed approximately 150 GDD51 later, or Thursday, Aug. 20 for the southwest region.

Detection of brown marmorated sting bug (BMSB) juveniles has increased in the Stevensville, Michigan area in Berrien County near the area where the pest was first detected in the region. Adult BMSB developing from these juveniles increase their feeding in late August and September, preparing for overwintering.

Peach harvest has moved to later season varieties such as Glowingstar, PF24C, PF19-007 and Beaumont. We are past the peak, with some growers finishing up this week. There are still many more peach varieties to be harvested into mid-September, mainly for direct sales markets. Fruit quality and size has generally been excellent this year.

Current problems are oriental fruit moth entries in fruit in tops of trees with reduced spray programs and brown rot in fruit damaged by insects. Obliquebanded leafroller damage to fruit is less common and tends to be a shallow groove. Growers should rotate fungicide types and modes of action to avoid fungicide resistance problems with brown rot. Relative level of bacterial spot symptoms has decreased as infected leaves drop from trees. Fruit symptoms due to bacterial spot are relatively light this year. Oriental fruit moth trap catches continue to be high in some orchards, but is generally declining.

Spotted wing drosophila (SWD) is a potential problem in peaches picked on the mature side of ripe trees. Infested harvested fruit may be stored at 35 degrees Fahrenheit or lower for at least 96 hours to kill developing eggs, larvae, pupae and adults. Peachtree borer moths are still flying in area orchards and have the potential for egglaying in limb and trunk wounds.

Sweet cherry growers need to maintain protectant fungicide coverage to reduce cherry leaf spot. Modest pruning can be done after harvest on trees that have filled their space.

Tart cherry trees exhibiting wilting or poor vigor foliage should be examined for gumming, sawdust-like frass and chewed areas due to American plum borer and peachtree borer larvae feeding on the trunk at or slightly below the soil line.

Plum harvest of Rubyqueen, Fortune, Castleton, NY6 and Toka is underway in the area. Stanley harvest is about 10 days off, depending on the site and crop load. Apple maggot, oriental fruit moth, codling moth and obliquebanded leafroller can infest fruit if it is not protected. SWD is also a potential problem for plums picked on ripe trees. Young plum trees should be examined for potato leafhoppers, an insect that can build quickly and stunt growth. Brown rot is the primary disease problem for plum fruit requiring control now.

Apple harvest of Zestar, Paula Red, Gingergold and SweeTango are underway with Gala harvest expected to begin about Sept. 7 in central Berrien County. See a more detailed list of apple variety harvest dates for west central and southwest regions. In general, apple finish and size looks very good. Stop drop sprays are a necessary tool for managing harvest.

Apple maggot adults continue being caught in good numbers for the fourth week at the TNRC. 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. In orchards where apple scab is present on fruit and leaves, growers should consider beefing up fungicide coverage shortly before harvest to help prevent pinpoint scab showing up in storage. Black rot symptoms are showing up on leaves and fruit in orchards with fruit mummies and in older orchards with dead wood that wasn’t pruned out.

We are still catching good numbers codling moth adults of 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 common in some orchards that still have active shoot growth. Sprays for San Jose scale crawlers, where present, were needed last week – crawler activity has been detected.

Pear harvest for processing of Bartlett is ongoing, with flesh testing 14-18 pounds with a penetrometer and a 5/16-inch diameter tip, skin removed. Harvest of Bartlett for fresh market (below 14-pound firmness) can generally be delayed to wait for better size and sugar. Gem harvest is expected about five to 10 days after Bartlett. Pears need to be protected against codling moth and oriental fruit moth. See a good fact sheet on harvest and storage of pears from Ontario.

Barlet pears

Bartlett pear harvest began this week on some farms in southwest Michigan. Photo by Mark Longstroth, MSU Extension

Small fruit

Japanese beetle trap catch numbers peaked in early August and have been declining for the past two weeks. Spotted wing Drosophila (SWD) is common in southwest Michigan with southwest region traps last week averaging 50 flies. Soft fruit or quickly ripen fruit is an excellent indicator you have SWD. Our traps are catching flies and trap numbers rise and fall depending on the availability of fruit, especially wild berries near commercial fruit plantings. SWD is a pest of ripening fruit and numbers increase as wild berries ripen and the fly moves from one ripening host to another. It has multiple generations every year so the population increases through the growing season.

Grape veraison is underway in some Concord vineyards, and is advanced where there is more light exposure. Early-coloring varieties such as Marquette and Geneva Red have already undergone veraison. The third generation egglaying of grape berry moth should be winding down in the coming week. See “Grape berry moth pressure lower in 2015 – control window approaching for southern Michigan” from Michigan State University Extension for more information.

Both juice and wine grape berries are resistant to fungal disease infections at this time. We are getting dew almost every morning, so this is the time when downy mildew can really move quickly in a vineyard. Growers need to protect leaves of susceptible varieties. Wine grape growers should apply a botrytis fungicide at veraison to reduce late-season fruit rots. In wine grapes, scout for potato leafhoppers. Grape leafhoppers is scarce in juice grapes. Japanese beetles are feeding on leaves in some vineyards. Usually only severe outbreaks of these insects require treatment, and pressure has been very light this year in most areas

Blueberry harvest has passed its peak in southwest Michigan. ‘Elliott’ harvest continues with good quality berries. Some U-pick businesses plan to be ending for the season in the next week. SWD numbers are generally low in sprayed fields, but SWD numbers in fencerows vary widely, depending on which wild fruits are ripe and their abundance. Growers will need to reapply protectant materials for SWD after rains where harvest will continue in the field. Frequent picking reduces the amount of time the fruit is available to SWD. Growers should be testing fruit for larvae.

Growers should apply fungicides to protect the fruit from anthracnose and Alternaria fruit rots and new shoots from stem blights such as phomopsis. Growers who have finished for the season are applying long last materials such as chlorothalonil. New shoot growth can be seen in fields where soil moisture is good. Fruit buds are starting to form in some early varieties.

Strawberry fields generally look good in irrigated and unirrigated fields. Be sure to protect newly emerging leaves against potato leafhoppers and foliar diseases.

Raspberry harvest has ended for summer red raspberries. SWD and Japanese beetles are out and can be a problem in raspberries. Harvest of fruit on fall bearing red raspberries and primocane bearing blackberries is expected to increase over the next few weeks. Growers with ripening fruit need to time their SWD controls with harvest and pay close attention to the pre-harvest intervals (PHI) on the pesticide label. Raspberries and blackberries are very attractive to SWD and growers need to pay close attention to this pest. See the SWD recommendations for caneberries at the MSU Spotted Wing Drosopohila website.

See also

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