Growers should be able to see the symptomatic leaf damage and infestation in corn fields if they were infested. First-generation moths prefer taller and earlier planted fields for laying eggs. Those who have non-Bt corn fields should scout for larval infestations.
To determine infestation levels and make management decisions, 50 plants in four or five locations in a cornfield should be checked for leaf infestations.
Larval damage is noticed as feeding scars and shot holes in plant leaves.
Chemical control of first-generation corn borer is justified when 25 percent of the plants in a sample show feeding damage and show presence of larvae. Chemical control of the pest must be applied before the feeding larvae bore into the stalks.
More detailed management information, including effective products, rates of application and others, can be checked in the High Plains IPM Guide at highplainsIPM.org. Trap counts from different locations are found at the Northeaster Colorado Pest Management Web site at nocopestalert.org.
Another pest that needs to be monitored in corn at the moment is the Banks grass mite (BGM). Rapid increases in infestations and population buildup of these tiny arthropods is influenced by hot and dry conditions.
Webbing and discoloration of leaves are often the first signs of BGM infestation.
Treatment for BGM management is justified when there is a visible damage in the lower third of the plant and small colonies present in the middle third of the plant before the hard dough stage.
For effective products, check the High Plains IPM Guide at highplainsIPM.org.
Extension has been checking grasshoppers in different sites but the nymph populations are still very low and do not warrant any management so far. Continue monitoring for these insects in yards, rangeland and crops.