Syngenta seed agronomists found corn earworm moths in western corn belt

Date:07-28-2011

As we go through the corn crop growing season, we see a multitude of insects. We generally start with black cutworm and end the season with corn earworm.

This insect is tough to scout for and to control because the actual damage is done inside the husk to the corn ear kernels during and after tassel stage.

Unless you get out in your fields, you may never see the damage until the corn is harvested and in the truck. Even if you get into your field to do some probing, there is not a lot you can do to control the pest because the corn is generally too tall.

You could be spraying every three days due to moth flight patterns (coming and going). The corn earworm penetrates through the silk area and creates a hole at the end of the ear.

The larvae will work their way down the rows, destroying kernels. In addition to feeding on the corn kernels, the insect is also introducing mycotoxins and alfatoxins to the ear, destroying grain quality.

Corn earworm is active throughout the year in tropical and subtropical climates, but becomes progressively more restricted to the summer months with increasing latitude.

Corn earworm is known to overwinter as far north as about 40 degrees north latitude, or about Kansas, Ohio, Virginia and southern New Jersey, depending on the severity of winter weather.

In northeastern states, dispersing adult moths arrive as early as May or as late as August due to the erratic nature of the weather.

The number of corn earworm generations is usually reported to be one in northernmost areas including most of Canada, Minnesota and western New York; two in northeastern states; two to three in Maryland; three in the central Great Plains and northern California; four to five in Louisiana and southern California; and upwards of seven in southern Florida and southern Texas.

The corn earworm life cycle can be completed in about 30 days.

In eastern Kansas, Syngenta agronomists have positioned 11 corn earworm pheromone traps from the Kansas/Nebraska border to the Kansas/Oklahoma border.

We selectively placed these traps in cropland that represents Kansas agronomic geographies. We have seen a significant increase in moths this year compared to last year, up as much as 4 to 5 times.

Last year, throughout the season we had a moth trap in St. Mary's, Kansas, and at the highest infestation period, we captured 151 moths.

So far this year, only three weeks into the trap placement, we have captured 101 moths in the same area at the highest infestation levels in a seven day period.

As shown here, our moth trapping locations have been exploding with moths in the last three weeks, well above threshold levels.

While trapping moths provides an estimate of when moths invade or emerge, and relative densities, pheromone traps are easier to use because they are selective.

The pheromone is usually used in conjunction with an inverted cone-type trap. Generally, the presence of five to ten moths per night is sufficient to stimulate pest control practices.