Use it, or lose it?
By Peter Darbishire
Industry acting to improve Bt refuge compliance.
By Peter Darbishire
Ten years into the use of Bt corn, the corn seed supply industry is generally
pleased with grower acceptance and use of integrated resistance management strategies
which require compliance with non-Bt refuge guidelines. However, there is still
room for improvement, according to a recent survey of growers by the Canadian
Corn Pest Coalition (CCPC), which comprises seed and plant biotechnology companies,
grower groups, extension and research advisors and scientists.
There are six stewardship principles in using Bt technology:
- the use of 20 percent of non-Bt corn seed in a production unit;
- planning so that the refuge is within a quarter of a mile of the Bt crop;
- keeping records;
- scouting the crop for corn borer feeding activity;
- matching hybrid heat unit ratings in the refuge with the main crop; and
- not spraying the refuge with a product that targets European corn borers.
These protocols help ensure that there is enough cross-mating between corn
borer adults that are susceptible and any that might have developed resistance
to the technology, thus producing susceptible offspring.
After years of experience, most users have learned to manage Bt responsibly.
A survey of Ontario, Manitoba and Quebec showed that in 2003, 82 percent and
91 of growers complied with the two key elements: use of a 20 percent refuge
and within the quarter mile proximity of the main crop. "We're really encouraged
by the improvement," says Dr. Mark Sears of the department of environmental
biology at the University of Guelph and co-chair of CCPC. In Ontario, the 20
percent refuge requirement remains the same at 86 percent of growers and the
proximity requirement increased from 90 percent to 93 percent. In Quebec, both
levels of meeting requirements fell off, which has prompted an increased extension
education effort to correct the situation.
The coalition is stepping up its campaign to further improve compliance. The
Canadian Food Inspection Agency, which oversees the industry's performance,
has the power to rescind the licenses of seed sellers if it is discovered that
there is lack of compliance. From the seed suppliers' viewpoint, it is unfair
for those producers who are in compliance if others are allowed to continue
While there is no obligation to buy all Bt and non-Bt (refuge) seed from the
same dealer, when a grower purchases Bt corn seed, he is required to accept
responsibility and buy and plant according to the prescribed protocols. For
2005, seed purchasers who are not obviously in compliance according to their
seed purchase records with an individual dealer can expect to be asked for proof.
If they are found to be non-compliant, they will receive educational information
and guidance to help correct the situation. In 2006, non-compliant growers can
expect to have their technology purchase refused. Basically, this follows a
sequence of discovery-correction-refusal for 2004-2005-2006.
Bt technology has proven its success to corn production and few will deny its
value. The new industry-wide compliance assurance campaign will lend growers
confidence that the technology will be viable and available well into the future.
Practical tips provided
Setting up a refuge of 20 percent
of corn acres with non-Bt hybrids takes some practical adjustments when planting
and is sometimes more difficult for small acreage growers than large ones. At
a recent open-house at the Listowel farm of George Van Eyk, a few suggestions
were offered by visiting growers.
- If a 12 row planter is being used, use the refuge hybrid in three row units
at one end of the planter to create a six row refuge across the field, which
is large enough to meet refugia criteria.
- If you use a herbicide tolerant (HT) hybrid that is tolerant to Liberty
herbicide: take care to use a Liberty tolerant non-Bt hybrid for the refuge
if a Liberty weed control is planned. A mistaken use of Liberty on a non-tolerant
hybrid will wipe out the refuge and result in the field being out of compliance!