Northwest Michigan tree fruit update – Aug. 24, 2021
Apples are ripening quickly with the heat and adequate moisture; we anticipate harvest to be seven to10 days ahead of normal.
The region is experiencing a lot of heat and humidity for August. This heat has moved apple development quickly. Daytime temperatures have been in the 80 degrees Fahrenheit; nighttime temperatures have also remained relatively warm in the high 60s to high 70s. According to Michigan State University Extension state climatologist Jeff Andresen, the hot and humid weather will continue until Saturday. There is also a chance of thunderstorms every day this week, and the highest chance of rain in is the north and western parts of the state. The highs will be in the 80s to 90 F, but with the heat index it will feel like 100 F. The weather is not expected to cool until the middle of next week.
The medium-term forecast for the region is a warmer and wetter September. The MSU Enviroweather station at the Northwest Michigan Horticulture Research Center has recorded 2,967 growing degree days (GDD) base 42 and 1,959 GDD base 50. We have not had any rain at the Northwest Michigan Horticulture Research Center since Aug. 11. With this year’s heat, we have accumulated almost the exact growing degree days as the Hart, Michigan, region. We are still at least a calendar week ahead of our normal growing degree days.
This heat has moved along the apple crop, and we are estimating to harvest apples seven to 10 days earlier than in the past. Growers on the Ridge are already starting to harvest Premier Honeycrisp and some early strains of Gala. They are also picking apples 10 days earlier than normal. Gingergolds are available at farm stands and Zestar are being picked as well. Our apples at the Northwest Michigan Horticulture Research Center are starting to color up nicely. We will begin our apple maturity sampling this week.
We are still seeing various sweet cherry blocks collapse across the region. We hypothesize that excess growth last fall and cold conditions are the culprit. We have also seen much more borer damage in sweet cherry trunks than in years past.
We typically do not see a lot of summer diseases or rots in apples in northwest Michigan. However, with all the heat and high humidity, growers should be on the lookout for these diseases. Growers are starting to see these diseases show up in apples in blocks around the state. Both Merivon and Pristine have zero-day preharvest intervals (PHI).
We caught an average of 9.6 oriental fruit moth this week at the Northwest Michigan Horticulture Research Center. These numbers are down from last week when we caught an average of 21 moths per trap.
Codling moth numbers were up from last week to an average of 9.6 moths per trap. According to MSU entomologist John Wise, the second generation codling moth flight is happening at the Trevor Nichols Research Center. Codling moth numbers around the state have not changed much in the past few weeks.
San Jose scale numbers are down for the past two weeks, and peak male flight was the week of Aug. 9. Crawlers are likely moving now and growers should be proactive in apple as this is the stage of this insect that can injure fruit. These numbers are notable and growers need to be sure to control this pest. We have seen the telltale signs of San Jose scale on our apples here at the station.