Degree-day models for Japanese beetle are used to predict emergence of adults in late spring and early summer. These maps use a sine-wave degree-day calculation with a lower developmental threshold of 50°F and upper threshold of 88°F with a January 1 biofix date based on preliminary adult trap catch data from Dominique Ebbenga and Dr. Bill Hutchison. Traps were deployed at Rosemount Research and Outreach center in Rosemount, MN, and the Horticultural Research Center in Excelsior, MN in both 2019 and 2020. 3 traps at each location in 2019 were checked twice a week, and in 2020, 4 traps were placed at each location and checked weekly. This model continues to be validated in the state and is included on this page as a preliminary forecast of emergence trends.

Current degree-days

Forecast degree-days

Japanese Beetle