MSU Extension

Weather report

After last week’s storm, the weather has returned to a typical August for northwest Michigan. Daytime temperatures over the weekend were up in the high 70s and low 80s. We had some cloudy days, but those seem to have cleared off, and there is a touch of fall in the air with recent cooler temperatures predicted to be in the 70s through tomorrow, Aug. 12. On Thursday, Aug. 13, the forecast is predicting hot temperatures to move back into the region for the remainder of the week and into the weekend.

Conditions remain dry across the region despite the 1.5 inches of rain from last week’s storm. Cloudy days over the weekend brought just a sprinkle of rain, which did not result in any substantial amount of rainfall. We have accumulated 2,481 growing degree days (GDD) base 42 and 1,606 GDD base 50. We remain spot on with our 25-year GDD accumulations.

Crop report 

We are still trying to assess the severity and extent of storm damage to grape vineyards in the Grand Traverse region. We would greatly appreciate individual reports on your observations, including dollar loss estimates for damaged fruit and trellis structures. Individual information will not be released, we are just trying to get a handle on the scope of the losses. Please email your individual reports to elsner@msu.edu.

Botrytis mold may infect storm-injured berries. See Michigan State University Extension plant pathologist Annemiek Schilder’s recommendations in “Protect hail-damaged grape clusters from Botrytis infection.” MSU entomologist Rufus Isaacs is concerned that either our native small fruit flies, Drosophila melanogaster, or spotted wing Drosophila may establish large populations in the injured fruit. Treatment options for these can be found in MSU Extension Bulletin E0154, “2015 Fruit Management Guide.”

We are still gathering information on damage to other fruit crops from last week’s severe storm. The storm seemed to travel in a band from west to east over the middle area of northwest Michigan; areas to the north and south of this band were not impacted as severely as orchards in the center of the storm. Orchards were affected here at the Northwest Michigan Horticulture Research Center (NWMHRC), and we have severe hail damage to our apples. We also lost about 15 trees at the NWMHRC. The storm’s path impacted orchards and vineyards from the Bingham area to south of Suttons Bay in Leelanau County. Growers in this area estimate they lost 30 percent of their leaves on the western half of their trees.

This storm system impacted the mid- to northern region of Old Mission Peninsula. Orchards and wine grapes on Old Mission also suffered hail damage. The hardest hit area is just south of Elk Rapids, Michigan, in Antrim/Grand Traverse counties. In this area, we have severe hail damage to all apples and some high-density trellis came down. We are still assessing the overall damage to the region, but we do know that the orchards and vineyards that were in the storm’s direct path were devastated while fruit outside this belt fared much better.

Tart cherry harvest is wrapping up, and growers in the north have a few more days to finish. The high winds of the storm beat up some tart cherries, but in most orchards where high winds occurred, growers were able to get the fruit off the trees before quality declined. Apples are sizing, and growers are assessing the hail damage to their orchards. We have some blocks where the hail caused some bruising, and these fruit have the potential to go to the juice market. Other orchards sustained pretty deep puncture wounds in the fruit as a result of the hail; there will be some growers that will not harvest the crop because the damage to fruit is so severe.

Pest report

Many growers are putting on post-harvest applications for cherry leaf spot, especially in orchards that had high levels of cherry leaf spot infection this season. Most of the northwest experienced very long wetting periods in May and June that were challenging for keeping tissue protected, and as a result, leaf spot took a foothold early in the season. Virus also impacted many trees this season. The combined effect of disease and virus infection throughout the region contributed to substantial early defoliation, and we encourage growers to try to keep the leaves that are remaining on trees into October. Growers should consider a fall foliar fertilizer to trees later in the season as leaves are beginning to senesce. An article on fall foliar applications is forthcoming – check the MSU Extension Fruit and Nuts News page.

Spotted wing Drosophila (SWD) numbers are continuing to rise throughout the northwest and although many growers have completed harvest, there are some orchards that have yet to be harvested in the far north. Because SWD numbers are high throughout the region, growers who are still planning to harvest cherries will need to keep fruit protected with tight intervals (seven days) and full covers. Some growers have used the three-day pre-harvest pyrethroid insecticides, Pounce or Danitol, when a material has been needed within three days of harvest. In SWD efficacy trials, we have found that Imidan is the most effective chemistry available for use against SWD. The data from our trials at the NWMHRC indicate this pest is extremely difficult to control and materials that are “excellent” for SWD are limited.

Cherry fruit fly activity increased at the research station this week. Many growers have made or are planning a post-harvest insecticide targeting cherry fruit flies and SWD to knock back their populations for next season. Apple maggot adults have been active for three weeks at the NWMHRC, and we found a total of 19 apple maggots in our traps this week. Codling moth also increased this week with an average of four per trap. Obliquebanded leafroller flight has slowed down and larvae should be larger and more visible at this time. Borer activity has also declined this week, with three American plum borers per trap, six lesser peachtree borers per trap and 0.3 greater peachtree borers per trap.

We have been monitoring for brown marmorated stink bug (BMSB) along orchard edges and in residential areas this season, but have not detected this insect. BMSB was detected in southern Michigan in Berrien and Kent counties last week. We encourage growers and consultants to bring any suspected BMSB specimens to the NWMHRC for identification.