West central Michigan tree fruit update – July 20, 2021
Tart cherry harvest is wrapping up in the region, and growers harvested 12.1 million pounds last week.
The weather continues to be seasonal, which has been helpful for the harvest season. Daytime temperatures have been in the low 80s with overnight temperatures in the mid-60s degrees Fahrenheit. According to the Hart Enviroweather station, we have accumulated 1,980 growing degree days (GDD) base 42 and 1,247 GDD base 50. We also had some significant rainfall on July 13-15, and we accumulated just over 2 inches of rainfall on Tuesday, July 13.
Sweet cherry harvest is through in the region, and tart cherry harvest is wrapping up. Growers are finding that there were perhaps a few more cherries out there than they initially expected. According to the CIAB report, the west central area harvested 12.1 million pounds last week, and the crop estimate is just over 20 million pounds total. Growers are looking forward to peach harvest, and apples are sizing nicely with the recent rains.
Pest and disease report
Primary apple scab season is over for west central Michigan. If growers were successful in controlling primary scab, there should be little concern for fruit scab. However, if scab was able to get a toe hold on foliage, fruit must continue to be protected.
On July 13 and 14, we had a cherry leaf spot infection period with a wetting span of 9 hours followed by another 18 hours of wetting; the first wetting period resulted in a low infection for cherry leaf spot and the second one was a moderate infection period. We have had some dry conditions that have kept cherry leaf spot infections on the low side, but we have also had rain events that have resulted in eight leaf spot infection periods since the first of June. Growers should keep up their leaf spot programs as we recommend that trees keep their leaves into September to minimize chance of damage if we have a hard winter.
We have observed higher than normal levels of powdery mildew in both apple and cherry. This disease is favored by hot and dry conditions, both of which we have had this season. This disease often takes a back seat to leaf spot and apple scab, but this year, this disease is much more of a concern. There is a lot of mildew on new shoot growth in tart cherries, and as a result, powdery mildew makes the leaves brittle and are easily removed during the shaking process. Unfortunately, there is little growers can do to eradicate this disease once we can see mycelial growth on the leaves.
If growers do have American brown rot in their orchards, we want to collect samples to test for resistance to the SDHI fungicides. Michigan State University’s George Sundin will be in the region tomorrow to evaluate a disease project at the Northwest Michigan Horticulture Research Center, but we are looking to collect brown rot samples while he is here. Please reach out to Nikki Rothwell at 231-342-4094 if you would like American brown rot in your orchard sampled.
We are fortunate to have Kenna Schwass on board in the west central region to help scout for insect pests. Schwass has previously worked as a scout with Wilbur Ellis, and last week she came up to the Northwest Michigan Horticultural Research Center for further training. Schwass set her traps last Thursday, so all numbers of insects in this report are from collections of five days in the field. All further data will be from one week, and traps will be checked on Mondays to have information to report on Tuesdays. Schwass will be scouting in peaches and apples for the remainder of the season.
We caught 16 peach tree borers in the past five days at one peach orchard in Elbridge, Michigan, and we caught another two borers in a New Era, Michigan, orchard. The trap was set at the west central station last week. We have caught an average of 5.7 greater peach tree borer moths this week in three traps in peaches.
We observed variability in oriental fruit moth in our three traps: zero in New Era, 31 in Elbridge and five at the west central station. We did not catch any oriental fruit moth this week in apple.
Codling moth numbers were zero at our trap in Elbridge and two moths were found in the codling moth trap in New Era. We found no San Jose scale or apple maggot in our traps. We did detect two obliquebanded leaf roller in our trap in New Era apples. We also found four black stem borers in one trap in New Era and five in the trap in Elbridge.