Studying Droplet Sizes to Combat Corn Earworm
April 12, 2010
Agricultural Research Service (ARS)
scientists have taken to the skies to combat corn earworm and help make U.S.
sweet corn more visually appealing.
Fritz, an agricultural engineer at the
Plains Agricultural Research Center in College Station, Texas, found in an
aerial study that spray rates and droplet sizes can make a big difference in
whether insecticides that control corn earworms are reaching the target.
The sweet corn grown in the United States is sold as a fresh market product,
so to attract a buyer it needs to be visually appealing. Corn earworms can
devastate both crop yields and the appearance of the ear. Some growers will
conduct aerial spraying operations as often as once every four days to control
Adult corn earworm moths lay their eggs on corn silks, and on leaves, husks
and stems near the silks. After the eggs hatch, the larvae travel along the
silks to feed on kernels where they remain protected by the husks. To be
effective, the insecticides must penetrate the plant canopy and reach the silks
where the larvae begin feeding soon after hatching.
Fritz and his ARS colleagues sprayed test plots three times with
insecticides approved for organic operations and then collected silks from ears
of corn growing on the plots to assess how much spray actually reached the
targeted silks. He sprayed some plots with 400-micron droplets and some with
220-micron droplets. The insecticides were mixed with water at
labelrecommended levels and sprayed at rates of either 5 gallons or 9
gallons per acre.
The results, published in the International Agricultural Engineering
Journal, showed that higher spray rates with larger droplets worked best to
ensure the insecticide reached the targeted corn silks. The results will guide
future corn earworm spraying operations, and the methods may be used in future
studies of spray rates for other crops and pests.
ARS is the principal intramural scientific research agency of the
U.S. Department of Agriculture (USDA). The
research supports the USDA priority of promoting international food security.