2005 Year in Review

From the Fields – European Corn Borer

Source: Jim Morrison, Extension Educator, Crop Systems, Rockford Extension Center, University of Illinois, Phone 815-397-7714; FAX 815-397-8620, E-mail morrison@uiuc.edu

Results of the annual fall survey for second-generation European corn borer revealed higher numbers than what we have observed the past couple of years. 50 Illinois counties (representing all nine crop reporting districts of the Agricultural Statistical Service) and 500 fields were sampled in the survey, which has been conducted since 1943, with the exception of 2 years.

Data from selected counties in the survey from 2005 are shown below.

County - %Plants Infested, 2005
Bureau - 40.8
DeKalb - 3.2
JoDaviess - 37.6
Knox - 7.6
Mercer - 45.6
Ogle - 10.8
Warren - 39.6
Whiteside - 6.4
Winnebago - 34.4

Borers per 100 Plants, 2005
Bureau - 94.6
DeKalb - 2.8
JoDaviess - 86.6
Knox - 0
Mercer - 144.4
Ogle - 16.8
Warren - 66.0
Whiteside - 8.6
Winnebago - 96.6

For 2005, the statewide average of plants infested by European corn borer was 24.2 percent, and the average number of corn borers per 100 plants was 34.4.

Comparable figures for 2003 were 32.5 percent infestation and 52 borers per 100 plants.

A cross-section of 10 random fields in each of the 50 counties was surveyed. Within each field, 25 consecutive plants were checked for any signs of European corn borer damage. After the number of plants infested was determined, two infested plants were split and the borers counted. It was not uncommon to find considerable variation field-to-field.

The objective of the fall survey is to obtain estimates of densities of second-generation European corn borer larvae. These estimates can be used to estimate economic impact of corn borers during any given year. The economic impacts can be compared over time and among counties and districts in the state. In addition, population trends can be determined.

Trying to predict, from the fall survey, the densities of corn borers for the following year is not very substantial. The level of diseases (or natural enemies) in overwintering larvae and weather conditions during the first flight of moths next spring will be key factors in regulating European corn borer populations in 2006.

Details of the European corn borer survey will be available in an upcoming issue of the Pest Management & Crop Development Bulletin and on the University of Illinois IPM web site at IPM.

by  Editor, theCity1.com
November 13, 2005