With the continuing hoopla concerning transgenic crops and the question whether or not to plant a BT hybrid in 2001, it may be worthwhile to refresh your memory of the status of the European corn borer population in Illinois. Last fall (November 3), we published (Bulletin, No. 24) the county averages for the percentage of plants infested and the number of borers found per plant. Densities of overwintering borers have been very low for 2 consecutive years. The statewide average percentage of plants infested in 2000 was 41.8%. In 1999, the percentage of plants infested was even lower (24.3%). The statewide average number of borers found per plant was only slightly greater in 2000 (0.38 borers per plant) compared with 1999 (0.29 borers per plant). Entomologists at Purdue University also have reported finding very low overwintering densities of borers. The magnitude of these low populations can be placed in better context by examining densities of this pest over the past 20 years. |
Illinois statewide averages (1982-2000) for European corn borer, pre-harvest.
European corn borer populations have been low in the past (well before the introduction of BT hybrids) and rebounded rather suddenly in some instances (1988 to 1989). No one knows for certain from year to year what the magnitude of corn borer infestations will be. This is especially true for the second generation of this pest. Because of the very low overwintering population of borers, I believe the spring flight of moths will be unimpressive this year. If environmental conditions are conducive to mating and egg laying this spring and midsummer, the second generation could provide some surprises. Of course, producers will always have the option of applying rescue treatments as needed.
With evidence that European corn borer densities are very low, is the use of a BT hybrid a sound pest-management approach for this spring? Is the use of a BT hybrid a good economic choice this spring? These are among many of the questions that producers undoubtedly were thinking about when they made seed selection choices this past winter. Given the following concerns: (1) continuing concerns (due in part to the extensive media coverage) about grain contamination and identity preservation issues, (2) uncertainty regarding the European and other overseas markets, and (3) the very low European corn borer population, anticipated demand for BT hybrids should continue to taper off. Until some of these issues are resolved, the anticipated commercialization of corn rootworm transgenic hybrids will continue to be slowed.--Mike Gray