MSU Extension

Weather

Warmer temperatures returned last week. High temperatures rose from the 70s into the high 80s. By the end of last week, soils were beginning to dry. Storms crossed the region on Sunday night (August 26-27). Rainfall totals range from 0.25 to 2 inches. Our growing degree day (GDD) accumulations are over three weeks ahead of normal. Plants and insect pest 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.

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

Insects

A few brown marmorated stink bug adults have been detected in black light traps in southern Berrien County. Brown marmorated stink bugs have caused extensive damage to fruit, vegetable and field crops in many eastern states. This is the third year this pest has been detected in Michigan and it is expected to eventually become a major pest in Michigan. Brown marmorated stink bugs can be confused with other common brown stink bugs found in Michigan. See an 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. 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 by refrigerating fruit or placing it in salt water and looking for the larvae migrating out of the berries. See an MSU Extension News article on sampling berries for SWD.

Small fruit

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

In brambles, fall raspberry harvest is underway. Growers report spider mites, Japanese beetles and potato leafhoppers. Spider mites and spotted wing Drosophila (SWD) are the primary problems in high-tunnel raspberries and blackberries. 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.

We continue to see redberry mite damage on blackberries. This is characterized by uneven ripening of drupelets with some turning black and others remaining red. Sunscald has also been found on blackberries with some drupelets drying up.

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

In grapes, veraison continues. There is a wide variation in sugars in grapes depending on the crop load on the vine and whether the clusters developed from primary or secondary buds. Although secondary clusters are catching up to primaries, they still lag behind, particularly in Concord grapes. Individual vineyards may vary considerably due to spring freeze losses.

The fourth generation of grape berry moth has reached the egglaying stage (2,430 GDD base 47). Consult the grape berry moth model at the MSU 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. Infested clusters ranged from 4 to 10 percent last week in vineyards we scout.

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 in research plots of Niagara grapes at the Trevor Nichols Research Complex in Fennville, Mich.

Bunch rots are becoming more noticeable with recent increases in rainfall and humidity. Botrytis bunch rot was found on Riesling grapes. Phomopsis can be found on rachises and clusters of some wine grape cultivars. Black rot is also quite noticeable on some cultivars.

Virus symptoms are becoming more obvious as the heat has abated. During September, 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 the Schilder lab for further information.

Tree fruit

San Jose scale adult male trap catch has increased somewhat. Normally, this insect has only two generations in Michigan, but may have a third generation in seasons that are unusually warm. We will continue to watch the trap counts to see if a third generation appears to be starting.

Peach harvest is winding down with end of season varieties such as Autumn Star, Encore and PF 35-007. Leaf yellowing and drop due to earlier bacterial spot infection and drought stress is occurring. Recent rains have increased brown rot symptoms on fruit. Peach flavor is generally very good.

Peaches are considered less vulnerable to spotted wing Drosophila, but can be infested if fruit stay on the tree until relatively soft – growers harvesting more mature fruit for direct marketing may need to watch out for this pest.

Cherry leaf spot infections are increasing with leaf drop due to this disease and drought stress is evident in the tops of some sweet and tart cherries. Recent rains have caused cherry leaf spot infections. Pruning of mature cherry trees should finish up soon so that trees are not stressed going into winter.

In apples, Gala harvest has begun as well as some spot-picking of Honeycrisp. Macs should start soon. Orchards with harvestable, economic crops should be protected against fruit rots, which are common where frosts or hot weather causes skin cracks and damaged lenticels. Gala varieties should be checked for pressure and starch levels. Leaf mottling of Honeycrisp is also present on the early ripening, Pink Lady look-alike Pink Rose.

Pink Rose leaf mottling.

For apple pests, this unusually warm season means that there will be a third generation flight of codling moth, resulting in larvae that will infest fruit if they can find them, but not develop sufficiently to survive the winter. Obliquebanded leafroller feeding on foliage is uncommon. Oriental fruit moth second generation moth flight is continuing at a low level – fruit entries by the larvae can be found. Leaf bronzing from European red mites, two-spotted spider mites and rust mites is common. Apple maggot fly catch has increased with recent rainfall.

Pear fruit are about 3 inches in diameter on Harrow Sweet with some blush developing.

Upcoming meetings

A high-tunnel production twilight meeting is planned from 6:30-8:30 p.m. Wednesday, September 5.