The corn earworm is one of the most
destructive insect pests of corn in the world. But here in Hawaii it is not
quite as destructive thanks to CTAHR (University of Hawaii College of Tropical Agriculture and Human Resources) plant breeders. Hawaii-bred corn
varieties are more resistant to the earworm due to their thicker and tighter
husks, thus limiting the number of larvae that can gain entry to the ear.
This allows growers to simply cut off the tips of the ears to remove any
damage that may have occurred.
Most of the eggs of the corn
earworm are laid on the young silks soon after the silks have emerged. Young
larvae crawl down the silk to feed on the kernels, soft cobs and the silk
itself. Luckily they also eat each
other, keeping populations low.
Corn planted early in the year is
not as seriously affected as is late corn because population densities
increase as the season progresses. Early plantings will have minimal damage;
later in the year one or two worms may appear in the tops of each ear of
corn.
Control
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To help
control the pest, between plantings destroy the crop residue or haul it off to
the compost bin. This eliminates places that would harbor the pest. Several natural enemies are present in Hawaii
and, in general, they keep the corn earworm at tolerable levels. In most cases,
control is simply a matter of cutting off damaged ends of corn at harvest.
For those gardeners who are plagued
with the corn earworm, here are some organic pesticide recommendations from the
University of California IPM program:
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- Bacillus thuringiensis (Bt) - may be dusted on silks every 3 days after 5 to 10% silk formation for partial control.
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