Southwest Michigan fruit regional report – September 4, 2012

Hot, dry conditions have dried the soil. Peach harvest is ending and apple harvest is underway.


Hot, dry conditions returned last week. High temperatures rose from the 80s into the 90s, with lows rising from the 60s into the upper 70s. By the end of the week, soils were dry in many areas. Storms crossed the region on Tuesday morning (September 4). Rainfall totals ranging from 1/10 to 2/10 of an inch. Our growing degree day (GDD) accumulations are over three weeks ahead of normal. Plants are not as far advanced due to the high temperatures and lack of moisture. These two factors in mid-summer caused development to slow or stop for several weeks. Insects and diseases seem to be lagging as well.

Southwest Michigan Growing Degree Day Totals from January 1 through September 2


GDD 42

GDD 45

GDD 50





Trevor Nichols




GDD since 8/26/2012




Check the MSUE Fruit page at the new MSU Extension site for more information.


A few brown marmorated stink bug adults have been detected in black light traps in southern Berrien County. This is the third year this pest has been detected in Michigan and it could become a major pest in Michigan. Brown marmorated stink bugs can be confused with other common brown stink bugs. See the MSU Extension News article on identifying brown marmorated stink bugs.

Spotted winged Drosophila (SWD) trap catches continue to increase. We expect numbers to increase through the rest of the fall. So far, this pest has been found in thin-skinned small fruit. Infested fruit becomes very soft and rots quickly. Larvae can be found in these fruits after crushing or placing the fruit in salt water and looking for the larvae migrating out of the berries after 15 minutes. See the MSU Extension News article on sampling berries for SWD.

Small fruit

Strawberry growth is good. In the high-tunnel strawberry plantings at the Southwest Michigan Research and Extension Center (SWMREC), day-neutral strawberry fruit production is picking up. SWD fly adults continue to be captured in traps, but the number of larvae recovered from fruit has declined. Powdery mildew is present on several varieties. Whiteflies have also been found on foliage, but do not appear to be causing economic damage.

In brambles, fall raspberry harvest is underway, blackberry harvest is ending. Spotted wing drosophila is a major concern. Growers also report spider mites, Japanese beetles and potato leafhoppers. In high-tunnel raspberries and blackberries, spider mites and spotted wing Drosophila are the primary problems. Female and male SWD have been trapped in increasing numbers in the high tunnel plantings at SWMREC, and larvae have been found in the fruit.

Blueberry harvest is finished in Van Buren County and growers are beginning the spot treatment of perennial weeds. Spotted winged Drosophila (SWD) numbers continue to climb, and some growers ended their season early because of this pest. See the MSU Extension News article on the pros and cons of post-harvest SWD sprays for more information.

In grapes, harvest of Niagara grapes began today. Sugar levels in grapes are increasing, but there is still considerable variation depending on the crop load on the vine and whether the clusters developed from primary or secondary buds. The fourth generation of grape berry moth reached the egglaying stage last week. Consult the grape berry moth model at the Enviro-weather website to check the progress of the model for your vineyard. Grape berry moth biofix was May 21 for Northern Berrien and Van Buren counties and May 19 in southern Berrien County. Grape berry moth trap catches have been low, and most infested clusters are found along vineyard borders. Fruit fly larvae can be found in some fruit, but they are not necessarily SWD.

Grape disease pressure has increased. Powdery mildew has been found on leaves and rachises of Concord grapes in Berrien Springs, Mich. Downy mildew has been detected at low levels in untreated sentinel plots at SWMREC and at research plots at the Trevor Nichols Research Center. Bunch rots are becoming more noticeable with recent increases in rainfall and humidity. Botrytis bunch rot has been found on Riesling and other wine grapes. Black rot is also quite noticeable on some cultivars. If the fruit are rotting and there are no lesions on the cluster rachis, then the rot is probably caused by black rot and not phomopsis. Virus symptoms are becoming noticeable and MSU’s Annemiek Schilder is planning to conduct testing on grapes suspected of being infected with viruses. If you wish to participate in this free service, contact her lab for further information.

Tree fruit

San Jose scale adult male trap catch increased somewhat last week. We may have a third generation in seasons that are unusually warm. We will watch the trap counts to see if a third generation appears to be starting. We are seeing rabbit feeding on young trees close to the ground.

Peach harvests are winding down with end of season varieties Autumn Star, PF35-007, Laurel and PF Big George. Recent rains increased brown rot symptoms on fruit. New York has reported finding spotted wing Drosophila in mature peach fruit.

Cherry leaf spot infections are increasing with leaf drop due to this disease and earlier bacterial canker has caused defoliation in the tops of sweet and tart cherries. Most recent rains have been cherry leaf spot infections. Pruning of mature cherry trees should finish up soon so that trees are not stressed going into winter.

Apples are harvesting about two weeks ahead of normal in southwest Michigan. Cortland is being picked and spot-picking of Honeycrisp continues with great flavor, but more than usual skin disorders. Golden Delicious are still green-skinned and testing immature (mainly 1 on the Cornell scale) according to starch tests, but shows signs of starch conversion starting. Be sure to check the MSUE Fruit page for the latest apple maturity updates.

Orchards with harvestable, economic crops should be protected against fruit rots, skin cracks and damaged lenticels. Leaf mottling of Honeycrisp is also present on the early ripening Pink Lady look-a-like Pink Rose. Hail marks on fruit on west side of trees have been the starting point for rots and insect entries.

Trap catches of codling moth and oriental fruit moth continue to be low, but fruit entries by the larvae can be found. Apple maggot fly catch has increased with recent rainfall.

Pear fruit are about 3 inches in diameter on Harrow Sweet with some blush developing. Harvest of Harrow Sweet at SWMREC will start this week. Fruit are testing an average of 16 to 18 lbs.

Upcoming meetings

A high tunnel twilight meeting will be held at SWMREC tomorrow evening (Wednesday, September 5) from 6 to 8:30 p.m. There is no charge for this meeting. Contact Jamie Styburski at the Berrien County MSU Extension office at 1-269-944-4126 for more information.

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