Canadian growers now have the option of purchasing hybrids genetically engineered to provide internal protection from European Corn Borer (ECB) throughout the growing season. Studies were done in 1996 and 1997 involving a collaboration of researchers from Ciba Seeds and Northrup King (now merged as Novartis), University of Guelph, Agriculture and AgriFood Canada, OMAFRA and OCPA. Fifty strip plots were planted across Ontario, covering up to seven heat unit zones, to assess Bt hybrids on their ability to reduce damage done by European Corn Borer (ECB), and their yield potential (or yield protection capability). At each location, forty plants per ECB generation were monitored in each of three hybrid types: a Bt hybrid, a non-Bt isoline (the genetic replica of the Bt hybrid, but without the Bt gene), and a high performance check hybrid for that region.

In 1996, infestations were highest in the more southern regions of the province where two generations of corn borer exist. In 1997, highest infestations occurred in the more northern regions. Results confirm that Bt hybrids reduced stalk tunneling drastically both years, from 7 to 8 cm in nonBt hybrids, to 1.4 cm or less of tunneling in Bt hybrids. Results in 1997 showed that both stalk and ear rot infection levels were significantly lower in Bt hybrids compared with their non-Bt counterparts.

Tunneling within the ear shank, a later season concern in 1997, was also reduced to a minimum in both events - ‘176’, which expresses Bt in the green tissue and pollen and is known as ‘NatureGard’ or ‘Maximizer’, and ‘Bt11’, known as ‘Yieldgard’, which expresses Bt in the ear as well as the green tissue and pollen. There was no significant difference between the two events.

Relative yields of the Bt and non-Bt hybrids depended upon ECB infestation levels. In general, Bt hybrids produced yields superior to the non-Bt isoline only when there was a high level of infestation (more than 6 cm of ECB tunnels/plant in non-Bt hybrids). In low (0-2 cm of tunneling) or moderate (2-6 cm tunneling) infestations, yields of all three hybrid types were generally comparable (Table 1).

Although some farmers have noticed that Bt hybrids stay ‘moist’ longer in the season and may require additional drying after harvest, in this study there was no difference in moisture content in the grain among the three hybrid types at harvest in either year. However, there was a difference in the percentage of stalks broken at harvest. In both years, Bt hybrids generally had a lower percentage of stalks broken at harvest than non-Bt hybrids, regardless of infestation level (Table 1).

Overall, Bt technology shows great potential in managing European corn borer. Yield may only improve when infestation levels are high. However stalk breakage and ear rot can be expected to be reduced even when ECB infestation is not so severe as to cause yield reductions. Growers must balance these benefits against the higher seed cost for Bt hybrids.