Corn Rootworm Hatch is Delayed but Underway

Expect 50 percent hatch between 684-767 degree days. Click here for current degree day accumulation for corn rootworm, courtesy of Iowa Environmental Mesonet, ISU Department of Agronomy.

Cool, wet spring weather delayed corn planting and the corn rootworm hatch, which is largely dependent upon soil temperature.  When soil temperatures accumulate between 684-767 degree days, 50 percent of the rootworm hatch occurs.

Although corn is not as far along in its development as it normally is at this time of year, there is still plenty of plant material available to provide a feast for the CRW larvae.  It won’t be long before newly hatched larvae begin feeding on corn roots.  Severe infestation can destroy nodes 4-6, which effect water and nutrient uptake.

Shortly after larvae begin feeding on roots, adult beetles begin to emerge from fields and begin feeding on pollen, green silks and leaves. The males emerge first, and the females follow about 5 to 7 days later.  Mating takes place, and then females will lay eggs toward the end of July through August.

Because of the wide variance in planting dates this year, it will be important to inspect every field – regardless of seed selection.  Rootworm beetles can move between fields in search of the best “buffet.”  A late maturing corn field may attract a large numbers of beetles if neighboring corn stopped producing pollen, for example.  Beetles may also move into corn and/or soybean fields which have an abundance of pollen-producing weeds, including volunteer corn, ragweed or foxtails.

Note areas where corn rootworm damage is the highest and create a plan of action if root injury is high.  To help assess injury, ISU Entomologist Aaron J. Gassmann developed an Interactive Node Injury Scale.  To help develop an action plan, keep best management practices in mind.

Field notes from 2013 will help you select seed products for 2014.  To prevent corn rootworm damage from reaching such devastating levels, plant a portfolio of products.  Remember, that in 2104 Latham® Hi-Tech Hybrids, will offer Agrisure DuracadeTM as another option in the fight against corn rootworm.