Southeast Michigan fruit regional report – Aug. 20, 2013

Crumbly raspberry disorder, necrotic leaf blotch and bitter pit in apples are starting to be seen at southeast Michigan fruit farms, and spotted wing Drosophila trap catches rise sharply.


Last week’s cool weather was welcomed by most growers and the lack of precipitation was good for some and bad for others. Cooler temperatures have persisted over the region for two weeks. Our season is running three to six days behind normal in terms of growing degree day (GDD) totals, however close to normal to a few days behind normal when I look at growth stages and the start of harvest of our fruit crops. Many areas have accumulated just over 100 GDD base 50 in the last week, for this time of the season that number is less than half of normal.

Soil moisture conditions are all over the board this season, and it seems as if for the last month growers fall into one of two groups, too little soil moisture or too much, with just few in the “just right” group. Rainfall totals for the past two and a half months vary widely across the region. Fruit crops at some farms are suffering from the waterlogged soils with tree and small fruits wilting, and at other farms, growers have been irrigating routinely over the last month.

East Michigan GDD totals for March 1 to Aug. 19





Commerce (Oakland)




Emmett (St Clair)




Flint (Genesee)




Lapeer (Lapeer)




Petersburg (Monroe)




Pigeon (Huron)




Romeo (Macomb)




Tree fruits

Apples continue to size well where soil moisture supplies have been adequate, however sizing has stalled where soil moistures have been short. Many apples are 2.625 inches in diameter. Harvest of Paula Red started at a few farms late last week. With this cooler weather, fruit color is excellent. Gingergold and Zestar are maturing quickly. Terminal bud set has taken place in most apple blocks and summer pruning continues. Retain applications continue to be made in several varieties.

As of yesterday (Aug. 19), bitter pit is just starting on Honeycrisp at a few farms. With the large fruit size in apples at most orchards this season, I am concerned about the possible development of bitter pit in large fruit. Growers need to consider additional applications of calcium in cover sprays.

Codling moth trap catch numbers were high in most blocks this past week, confirming that we are now in the second generation adult flight. It is too early to control this latest flight, especially with these cooler temperatures. Most growers quickly biofixed for the second generation flight two weeks ago, meaning that it will be late next week for the best time to control the flight. Trap catch numbers are generally in the range 12 to 20 moths per trap.

I continue to catch apple maggots, but their numbers are down this past week, most likely due to the lack of rainfall. I continue to catch apple maggots only on yellow sticky cards. I am continuing to see low numbers of many other insect pests, including oriental fruit moth adults, fall webworms, obliquebanded leafroller larvae, Japanese beetles, wooly apple aphids, potato leafhoppers and green apple aphids. Apple rust mites continue to be found with dropping numbers, mainly from predators feeding on them. There are a few European red mite and two-spotted spider mite hotspots in a few apple blocks, but generally their numbers are well below thresholds levels. No brown marmorated stink bugs have been trapped or reported in the region this season. There continues to be high numbers of predators being seen this season.

Necrotic leaf blotch symptoms started to be seen late last week. This physiological disorder mainly effects Golden Delicious and its related bud sports. Leaves first begin to show irregular-shaped spots and then yellow and drop to the orchard floor. We continue to see Sooty blotch and fly speck symptoms in apples.

Pears have continued to size this past week, with most 2.25 to 2.5 inches in diameter. Damage from spring frosts is becoming very apparent in the last few weeks.

Peach harvest continues with Red Haven harvest winding down at most farms. The first picking of most varieties of peaches have good size and finish, however some growers are reporting the size goes down dramatically with the rest of harvest for that variety. No brown marmorated stink bugs have been trapped or reported in peaches in the region. Brown rot has been seen at a few farms in the past two weeks, but only in blocks that received hail in the past month or so. Peach scab has been seen in the last two weeks in a few blocks. Fruit, twigs and branches continue to ooze from bacterial spot infection. X-disease continues to be seen.

Plums continue to color for European varieties, and Japanese plum varieties are being harvested.

Small fruits

Strawberries continue to rebound from renovation. Newly planted berries are continuing to runner well. Potato leafhopper feeding and leaf curling is being seen in most new and renovated plantings.

Raspberry harvest of fall red raspberries and blackberries continues. Spotted wing Drosophila (SWD) have continued to be caught in traps at most farms in the last week. Trap catch numbers are continuing to rise dramatically. Trap catches in both raspberries and blueberries have been very high in southwest Michigan in the last three weeks and my Michigan State University Extension colleagues are seeing the same trend now. Growers need to be on the lookout for first trap catch at their farm.

Two-spotted spider mite populations are high in a few bramble patches in the past week. Most of the farms that are affected need to be treated with a miticide. Japanese beetle populations have continued to drop in the past two weeks. Potato leafhoppers are being seen in both new and established raspberry plantings.

A disorder known as crumbly berry has been seen at several raspberry farms across the state. While this disorder can be caused by a variety of factors, this year it appears that the lack of pollination and cooler temperatures at bloom time are the main causes. Berries at harvest are small, misshapen and fall apart when harvested. While most farms only have a few varieties impacted by this disorder, the combined list of varieties impacted at all farms across the region is long. Tarnished plant bugs, two-spotted spider mites and viruses can also cause crumbly berries. Phytophthora root rot disease continues to be seen at farms that had excessive rainfall over the past two months.

Blueberry harvest continues on many varieties, many growers said this week they are now a bit more than half-way with completing harvest with an excellent crop being harvested. Spotted wing Drosophila have been trapped in blueberries at several farms in the last week. Trap catch numbers are continuing to rise. Growers need to be on the lookout for first trap catch at their farm. Trap catches in both blueberries and raspberries have been very high in southwest Michigan in the last three weeks and my colleagues are seeing the same trend now.

Blueberry maggot trap catch on yellow sticky traps continues with declining numbers in most plantings. Birds, mostly robins, starlings and redwing black birds, continue to feed heavily in most blueberry plantings.

Grape cane growth has started to slow down. Concord grapes are starting veraison. Japanese beetle populations continue to decline in grapes. Grape berry moth adults continued to be caught in traps in steady numbers. Downy mildew continues to be seen in many grape plantings, most from infection earlier this season when conditions were warm and moist. Powdery mildew, favored by cooler temperatures and moist conditions, is present in many vineyards in lesser amounts later this season.

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