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Watch for Late-Season Insect Problems

July 14, 2000
At this point in the growing season, things are progressing well. Disease and insect problems have been isolated. There may still be some concerns as the season progresses. The first potential problem is grasshoppers. The moisture we received during the later part of June has kept the grass green and the grasshoppers out of our crops. As the temperatures rise and rainfall dwindles, look for these grasshoppers to move into green crops. Border treatments with carbaryl or malathion can reduce the movement of these insects into corn and beans. As with most insects, grasshoppers are easier to control when they are small, so scout those waterways and field borders soon before these insects move into your crops.

There is one other insect that has the potential of sneaking up on us later in the season. This insect is the southwestern corn borer. First flight activity peaked in the first week of June. Trap catches were quite high in Massac County and moderated as one moved north into Franklin County. Infestations of first-brood southwestern corn borer have been locally heavy but generally not much of a concern. The second flight has begun in southern Illinois, with high catches reported in Massac and Franklin counties. These numbers reflect the potential for significant infestations of second-brood larvae. The peak egg-laying period should occur during the second and third weeks of July. Later plantings of corn could be severely affected by these second-brood larvae. Treatments for second-brood larvae may be warranted when 20% to 25% of the plants are infested with eggs or newly hatched larvae. The feeding activities of the southwestern corn borer can increase lodging and dropped ears during harvest. Early harvest of severely infested fields can reduce these harvest losses.--Mark Hoard

Author: Mark Hoard

The Pest Management and Crop Development Bulletin
Executive Editor: Kevin Steffey, Extension Entomologist

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