2008 Year in Review

From the Fields

Results of the 2008 annual fall survey for second-generation European corn borer (ECB) showed the lowest density of borers ever determined from this survey. Currently 49 Illinois counties (data from 3 counties have not yet been reported) and 494 cornfields have been sampled in the survey, which has been conducted since 1943, with the exception of 1997 and 1998.

The number of corn borer larvae per 100 plants from selected counties in the survey over the past three years is shown below.

County	Larvae per 100 Plants, 2008	Larvae per  100 Plants, 2007	Larvae per 100 Plants, 2006
Bureau	0	4.6	25.6
DeKalb	0	1.2	0.4
JoDaviess	12.8	7.2	25.2
Knox	0	2.2	23.4
Mercer	3.6	16.8	23.0
Ogle	0	3.6	0.0
Warren	0	14.8	113.4
Whiteside	3.6	7.2	3.6
Winnebago	1.2	41.6	12.8

For 2008, the statewide level of infestation by ECB was 8 percent, and the statewide average number of larvae per 100 plants was 9.6. Comparable figures from 2007 were 10.7 percent infestation and 13.4 larvae per 100 plants (this was the second lowest density ever determined from these surveys). Figures from 2006 were 33 percent infestation and 23.2 larvae per 100 plants.

Ten randomly selected fields in each of the 49 counties were surveyed. Within each field, 25 consecutive plants were checked for any signs of second-generation ECB damage. After the number of plants infested was determined, two infested plants were split and the larvae counted.

Kevin Steffey and Mike Gray, University of Illinois Extension entomologists and coordinators of the survey, indicated that in 2008

- zero ECB larvae were found in 16 of the 49 counties surveyed
- there were zero ECB larvae found in 418 of 494 fields, or 85% of the fields surveyed
- only 28 fields, or 5.7% of the fields surveyed, had more than 50% infestation

The impact of transgenic Bt corn on ECB populations in Illinois has been dramatic. But the 2008 weather pattern also played a role in reducing ECB densities, according to Steffey and Gray. Heavy rainfall in some areas caused mortality in first-generation corn borers that contributed to the overall mortality of borer population.

Details of the ECB survey can be found in issue 24 of the University of Illinois Extension Pest Management & Crop Development Bulletin.

by  Editor, theCity1.com
November 14, 2008