Recent weather across Michigan has been mixed, with cooler conditions in the north and warmer-than-normal temperatures in the south. Precipitation has been heaviest in the Upper Peninsula and north/central Lower Peninsula, while areas south of Lansing received less than 0.25 inches of rain last week. Growing degree days (GDD50) show southern Michigan is nearly a week ahead of normal, while the Upper Peninsula lags behind—an unusual pattern.
Looking ahead, light precipitation is expected across upper Michigan by Friday, followed by dry and cooler conditions through the weekend. The 6–10-day forecast predicts warmer and slightly wetter conditions, although early May may see near-normal temperatures and drier weather.
Chestnut orchard management
It's a busy time in Michigan chestnut orchards. Growers should be removing mouse guards, prepping irrigation, collecting soil samples, and applying fertilizers. Spring is also ideal for painting tree trunks to prevent southwest disease and beginning pest scouting.
Pest monitoring
Black stem borer adults become active in late April or early May, coinciding with blooming forsythia and around 100 GDD50. These tiny insects (about 0.08 inches) attack stressed, small-diameter trees. Monitoring can be done using simple ethanol-baited traps placed along orchard perimeters. If caught, young trees near woodlots should be treated with trunk-applied pyrethroid insecticides to prevent colonization. Later in the season, remove and destroy infested trees and pruning debris to limit future infestations.
European red mites overwinter as eggs and become active early in the season. Early scouting for eggs and nymphs is essential. Predatory mites can help control pest populations, so limiting broad-spectrum insecticide use preserves these beneficial species. Dormant oil sprays are effective against overwintering eggs, while other miticides are recommended if populations rise during the season.
Disease management
Chestnut blight symptoms are visible now. While there are no commercial treatments, infected branches or trees should be pruned or culled and burned or buried to limit disease spread.
For more detailed guidance, growers are encouraged to reference the Michigan Chestnut Management Guide.
To view the full report, click here.
For more information:
Michigan State University
Tel: +1 517 355 1855
www.canr.msu.edu