Flooding and high soil moisture have negative impacts on soil-dwelling insects and without a doubt the most important pest affected by heavy rains in our area is corn rootworm, explained Ada Szczepaniec, SDSU Extension Entomology Specialist.
"Corn rootworms have begun to hatch in eastern South Dakota, which is the area most heavily hit by recent high precipitation. Highly water-saturated soils or areas with standing water that persist after corn rootworm hatch contribute to higher than normal mortality of the larvae," said Szczepaniec, of the corn rootworm larvae which damage corn roots and cause severe yield losses to corn producers.
She explained that when corn rootworms hatch in flooded or wet soils they are likely to suffer significant mortality through drowning or attack by beneficial microbes and fungi that thrive in wet conditions. Heavy rains and flooding that occurred in eastern South Dakota early last summer contributed also to a major decrease in corn rootworm populations in corn and lessened their pressure.
Corn rootworms usually hatch around V5 stage of corn. Because of delayed planting in the northern parts of the state we will likely see larger than usual differences in corn maturity along I-29. In addition, timing of hatch for rootworms will be much earlier in the south than the north. "Regardless of timing, heavy rains are saturating the soils across eastern South Dakota and contributing to corn rootworm larvae death," Szczepaniec said.
She added that there are no steps that producers need to take with respect to this pest at this point. "Good news for corn growers is that corn rootworm pressure may again be relatively low this year."
She reminds all corn producers that not all cornfields are at risk for corn rootworm damage regardless of weather conditions. "Fields that should be inspected for corn rootworm activity include fields that were planted to corn last year, fields that had high numbers of adult corn rootworms last summer, and fields where the same Bt hybrid has been used for three years or more," Szczepaniec said.
Source : SDSU