MSU Extension

Weather

Last week was cooler. High temperatures fell from the 90s into the 70s. Storms crossed the region on September 4 and 8. Rainfall totals ranged from 0.5 to 1 inch. Our growing degree day accumulations continue over three weeks ahead of normal. Plants are not as far advanced as these degree day totals because high temperatures and lack of moisture in mid-summer caused sluggish development until rains returned in mid-August. Insects and diseases are lagging as well.

Insects

Spotted winged Drosophila (SWD) trap catches are increasing dramatically. Numbers will increase through the rest of the fall. This pest has been found in many small fruit plantings. Infested fruit becomes very soft and rots quickly. See the MSU Extension News article on sampling berries for SWD.

Small fruit

Strawberry growth is good in June-bearing fields. In the high-tunnel day-neutral strawberry plantings at the Southwest Michigan Research and Extension Center (SWMREC), flower production has increased with cooler temperatures and fruit production is picking up.

SWD fly adults continue to be captured in traps. These strawberries received little insecticide treatment for SWD and larvae can be recovered from about 50 percent of the fruit. Powdery mildew is present on several varieties. Whiteflies are not a usually a pest of strawberries, but we believe they came into the tunnel on strawberries produced in a greenhouse. While the whiteflies themselves appear to be doing little damage, the honeydew they produce has caused sooty mold on the leaves.

In brambles, fall raspberry harvest continues. Spotted wing Drosophila is a major concern. In high-tunnel raspberries, spider mites and SWD are the primary problems. Female and male flies continue to be trapped in the SWMREC high tunnels and larvae are becoming common in the fruit. Losses due to larvae are running about 50 to 60 percent. Growers with field plantings of raspberries and blackberries have also commented on the challenges of controlling SWD.

Blueberry flower buds are forming at the shoot tips of healthy plants. There is a fair amount of new growth visible in many fields. Shoots that are growing rapidly now will not set fruit buds this year. Growers should examine drought-stressed plantings to assess the extent of damage to this year’s shoots. Live shoots that have lost their leaves will not set fruit buds and may die during the winter. Many plants that suffered damage during this year’s drought will need increased pruning and in severe cases, cutting down to the crown may be the best alternative.

In grapes, harvest of Niagara grapes continues and should end Thursday (September 13). Sugar levels in the grapes are good (15 to 16 brix), quality has been good, and yields are higher than expected after the freezes. Concord harvest is expected to begin on Friday of this week (September 14) and is also expected to move quickly. Wine grape harvest is underway as well with generally good yields and high sugars.

The fourth generation of grape berry moth are flying and laying eggs. 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 along vineyard borders. Fruit fly larvae are present in some fruit, particularly where there has been hail damage, but they are not necessarily SWD. 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. Sour rots are showing up in some vineyards. Virus symptoms are becoming more noticeable with cooler weather. MSU’s Annemiek Schilder is testing grapes suspected of being infected with viruses again this fall. If you wish to participate in this free service, contact her lab for further information.

Tree fruit

Due to the hot season, the third generation of San Jose scale could be significant in orchards where earlier generations were not controlled. The San Jose scale biofix for the third generation was set at August 27, based on male moth trap catch at the Trevor Nichols Research Station. Crawlers are expected at 400 to 450 DD base 51 F after this biofix, which is 2,903 to 2,953 DD base 51 F from January 1 at the Bainbridge/Watervliet Enviro-weather station. Based on the Enviro-weather forecast for this station, we estimate that crawlers of this insect should begin emerging approximately September 21. Hot or cold weather could push this prediction earlier or later.

Bucks are rubbing their antlers on trunks and scaffolds of young peach and cherry trees.

Peach harvest has ended with the varieties Victoria and PF Big George. Rhizopus rot, causing a dark black fungal mat on mature fruit, has become more common with recent rains. Some peach orchards have ended the season with relatively low nitrogen levels because growers did not apply fertilizer due to poor crop. Nitrogen applications to such orchards, especially if on sandy sites with little residual fertility, may need to be timely in 2013 in order to avoid retarded green-up and growth.

The beard on this peach is Rhizopus rot. Photo credit: Bill Shane

Cherry leaf spot infections are increasing with defoliation in the tops of sweet and tart cherries. Recent rains have been cherry leaf spot infections.

Apple harvest is about two weeks ahead of normal in southwest Michigan. Red Delicious fruit (Red Chief types) at SWMREC are testing mature (3 on the Cornell starch scale and firmness 17 lbs) according to guidelines for apples destined for long-term controlled atmosphere storage. Apple maturity updates are posted on the MSUE Fruit Page on Thursdays.

Orchards with harvestable, economic crops should be protected against fruit rots, which are more common this year due to weather-related skin cracks and damaged lenticels. Trap catches of codling moth and oriental fruit moth continue to be low, but fruit entries by larvae can be found. The low catch of codling moth is attributed to the general lack of apple fruit. Apple maggot fly catch at Trevor Nichols Research Station continues, but at a relatively low level.

Pear harvest of Harrow Sweet was generally completed last week. Harvest of Bosc, Shenandoah, and Concorde will end up the season.