Overall, corn rootworm populations have been dampened in Iowa this season. A few factors likely contributed to this decrease:

1. An exceptionally harsh winter may have increased mortality of overwintering eggs.
2. Saturated soils in June may have increased mortality of corn rootworm larvae.
3. Some fields with extremely high corn rootworm populations were likely rotated out of corn, which disrupts the pests' life cycle. Since 2011, corn production has decreased in Iowa by one-half million acres according to the USDA..
4. Cooler summer temperatures translate to a slower growth for corn rootworm larvae in the soil, and this may increase natural mortality from insect-killing fungi and other factors.