The use of soil insecticides on the current year's crop is still the most reliable control method. If this method is used, it should be under the supervision of trained pest management personnel. To have a reasonable chance of success, begin weekly scouting in early July. Note that strict use of calendar dates in timing of treatment is not recommended since there may be as much as 3 weeks variation in optimum treatment timing from year to year. When beetle numbers first reach or exceed the above threshold, apply a residual insecticide.
Residual activity is reduced by overhead irrigation or rainfall after application.
If beetles reinfest the field, make a second application when population levels reach one beetle per two plants. The cost of two treatments will exceed that of a single soil treatment applied at planting or first cultivation the following spring. In continuous corn, if you do not have scouting data from the previous season for the full beetle activity period, consider a soil insecticide application at cultivation or planting as a precautionary measure. Many fields never develop a rootworm problem. Using both adult control the previous year plus soil insecticide the current year is not recommended.