Japanese beetle is an invasive insect capable of feeding on corn and soybean. This pest has been in Iowa since 1994 but its distribution in field crops is considered sporadic around the state. Statewide populations were low in 2014 and it is unclear if pressure will be significant this year. Literature shows Japanese adults need about 1,030 growing degree days (base 50°F) to complete development and will continue emergence until around 2,150 degree days. Based on accumulating degree day temperatures in 2015, Japanese beetle adults should be active in some areas of southern Iowa this week (Figure 1). To more accurately predict adult emergence in your area this summer, use this website to generate up-to-date information. Click on the “View Degree Day Map” button in the left corner of the page, and then set the parameters for degree days to create a new map. Make sure to set the start date to January 1 of the current year and the end date to today; set the base temperature to 50°F and the ceiling temperature to 86°F.
Iowa State University
Hodgson, Erin W., "Japanese Beetles Begin Emergence" (2015). Integrated Crop Management News. 340.
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