Adult corn rootworm beetles emerge in July and early August and after feeding on foliage and pollinating silks proceed to lay their eggs at the base of corn plants. Eggs overwinter in the soil until they hatch into larvae the following spring. If corn is planted again the following season, the larvae feed on the corn root system causing corn to lodge and reducing grain yield. Thus, rootworm is only a problem on continuous planted corn. An exception is the NCR strain in the north central states, where eggs remain dormant for more than a year. This strain has become a problem in the Dakotas, Minnesota and other states.
* Southern corn rootworm does not overwinter in Ohio.
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If one or more adults are found per plant in continuous corn, then a soil insecticide is needed the following spring.
In the case of 1st year corn, the number of adults allowed per plant is reduced to 0.7 due to a higher proportion of ovipositing females that migrate more readily than male rootworm beetles.
Peak adult activity appears later in 1st year corn and late planted due to migration and/or late silking.
Five or more adults per plant may cause heavy silk clipping and a rescue treatment may be warranted if pollination is disrupted.
Ambush*
Asana*
Capture*
dimethoate
Imidan
Lannate*
Lorsban*
Malathion ULV
Mustang*
Penncap-M*
Pounce*
Sevin
Warrior*
* Use is restricted to certified applicators.
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