05-24-16 CSU Ext Pest Alert: First generation European corn borer monitoring and management…

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First generation European corn borer monitoring and management

Written by: Assefa Gebre-Amlak and Frank Peairs, Colorado State University

Some of the adult European corn borer monitoring sites in northeastern Colorado are showing emergence of the moth. First generation moths prefer taller and early planted fields for laying eggs; cornfields should be scouted the next 2-3 weeks. For European corn borer moth emergence and duration of infestation, check our pest alert web site (www.nopestalert.org) where trap counts from different locations and years are found.     

Some hybrids have useful resistance to the first brood of European corn borer, which feeds in the whorls and later enters the stalk. Control can be expected with these Bt corn hybrids, except those containing only events that target corn rootworms. All non-Bt corn fields need to be monitored to manage the pest before economic damage is done.

European corn borer usually goes through two generations each year. The young larvae feed first on the leaf near where they hatched. As the larvae grow, they move to the whorl or leaf sheath area, and feed. When leaves emerge, the “shot hole” feeding signs in the leaves can be seen. Most of the mature larvae will bore into the stalks, feed, and finish development there. Second generation larvae cause ear damage, tunneling in the shank and feeding on silks, kernels and cobs. Signs of infestation include: dropped ears, broken shanks, stalk breakage, sawdust-like castings on leaves, and holes in the stalks.

To determine infestation levels of first generation and make management decisions, 25 plants in 4 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% of the plants in your 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: www.highplainsIPM.org.

Submitted to the BARN by:

Jeannie S. Lambertson, Administrative Assistant, Colorado State University, GOLDEN PLAINS AREA EXTENSION; 181 Birch Avenue, Akron, CO  80720; 970-345-2287; email: jeannie.lambertson@colostate.edu