Bt Corn Growers' Guide Now Available

GROWER RESOURCE
Bt Corn Growers' Guide Now Available
By Albert Tenuta, Field Crop Pest Management Specialist, OMAFRA and Ken Hough, Director, Research and Market Development

Many Ontario corn growers have evaluated the performance of Bt corn hybrids on their farms, following the initial introduction of this technology in 1996. Indeed, corn growers in many regions of the province now recognize the potential severity of yield and grain quality loss to European corn borer (ECB) which can occur, despite the huge efforts exerted by corn breeders to control ECB damage through traditional corn breeding approaches.

Extensive field scouting and on-farm crop performance studies – conducted by seed companies in collaboration with OMAFRA extension specialists and University of Guelph/AAFC researchers – have clearly demonstrated two points. First, ECB infestations vary substantially from place to place and year to year. Although predicting infestations has been notoriously difficult, Bt corn has provided producers with an effective management option for ECB. Provincial field results have shown a significant return on investment (10-15 per cent yield advantage, in addition to grain quality improvements) where ECB populations are moderate to heavy. One can see why this production tool has increased in popularity to where about 35 per cent of Ontario’s corn acreage in 1999 was planted to Bt hybrids.

As the usefulness of Bt corn hybrids becomes more widely accepted and Bt corn acreage expands, corn producers (and seed companies, researchers, extension personnel, and government regulators) have a keen interest in preserving the effectiveness of this technology for the long term, including minimizing the potential build up of ECB resistance to Bt.

To address growers’ questions and desire for information on Bt corn, A Grower’s Handbook For Controlling European Corn Borer With Bt Corn, has been developed by the Canadian Corn Pest Coalition (comprised of grower representatives through OCPA and AGCare; public sector representatives from OMAFRA extension, University of Guelph and AAFC researchers; and seed company agronomy and research personnel). In an attractive and easy-to-read format, this publication provides generic information collectively supported and promoted by all Coalition partners, including all seed companies, on such topics as:

What is Bt corn, how does the Bt gene work, and how is it put into corn plants?
What is the ECB and what does ECB damage look like?
Why manage ECB?
Rating your risk to ECB damage.
How does ECB resistance to Bt corn develop?
Managing resistance through the high dose/refuge strategy
What are my refuge planting options?
Can other plants be a refuge?
Does Bt corn protection extend into adjacent non-Bt corn?
What are the impacts on natural ECB enemies, and other non-target organisms, such as the Monarch butterfly?

Copies of the Bt corn growers guide will be available through your local seed corn dealer, seed corn company representatives, from OMAFRA personnel and offices, from OCPA, or on the Internet shortly at the OCPA web page www.ontariocorn.org/btguide.html (with links from many other sources such as University of Guelph, OMAFRA and seed company web sites).

Recommendations
From the corn grower’s perspective, there are only a few key insect-resistance management (IRM) recommendations which need to be followed to prevent the build up of Bt-resistant ECB on your farm. These are (from the Bt corn grower’s handbook):

Grow Bt corn hybrids in fields that are at economic risk of European corn borer damage.
Keep careful and accurate records as to where Bt and non-Bt corn hybrids are planted.
Establishment of “refuges”, another key aspect of an IRM plan. Refuge areas are to be planted to non-Bt corn hybrids to help prevent the development of Bt-resistant corn borers. The goal is to have a minimum of 20 per cent of acres planted to non-Bt hybrids to ensure an adequate supply of natural ECB moths not exposed to the Bt protein. The 20 per cent refuge can be implemented as complete fields, blocks, headlands or alternate strips that are at least 6 rows wide. Bt corn fields must be planted within 400 metres (1/4 mile) of the non-Bt refuge.
Continue to scout for insect and disease problems in both Bt and non-Bt fields. Although Bt corn is effective against the European corn borer it will not eliminate corn diseases or other common corn insect pests such as cutworms, wireworms, white grubs, seedcorn maggots, corn rootworms, aphids or mites.
Monitor for resistance in European corn borers to Bt corn. If feeding damage occurs, investigate the cause. If needed, get help to identify feeding caterpillars. If European corn borer larvae or excessive damage are discovered, resistance to Bt corn is a possibility and the situation should be investigated. Verify from field records that Bt corn was planted where excessive damage or larvae are observed. Note the Bt hybrid. Notify seed company representatives immediately if you suspect a problem. The Canadian Corn Pest Coalition along with Health Canada have developed procedures to determine if resistance is occurring.

OCPA strongly encourages all corn growers to be familiar with, and follow the Bt corn/corn borer IRM strategies as explained in the Bt corn growers’ handbook.