A refuge calculator tool to help you choose your corn hybrid

Sunday, December 4, 2011

Log on to the Better Farming website and you'll find a link to a handy tool, which will help you comply with refuge requirements when planting Bt corn varieties

by DON STONEMAN

Choose your Bacillus thuringiensis (Bt) corn hybrid with care. And don't forget to match it up with the right amount of refuge hybrid if one is required. That's one piece of advice crop experts stress and there's a new tool to help you do that.

Corn hybrids marketed for the first time in 2012 are available in a searchable fashion on Better Farming's website at www.betterfarming.com

Readers can look at that site, choose a hybrid suitable for their needs and, if it is a Bt hybrid, look at a refuge calculator to determine if their choice must be planted with a refuge hybrid.

The refuge calculator tool was launched last spring. For every hybrid where a refuge is required, there is a hybrid that can be matched. Seed corn companies have agreed to keep it as up to date as possible, says University of Guelph professor Art Schaafsma, chair of the Canadian Corn Pest Coalition. The refuge selector is available at http://www.refugeselector.ca/

The coalition's website address is http://www.cornpest.ca/
Growers should strive to comply with refuge requirements when planting Bt corn varieties; there are consequences if they don't, warns Schaafsma.

While a number of companies are offering single-bag refuge technologies (with the refuge seed mixed in with the Bt seed corn), there are still a large number of corn varieties that require a refuge in the same field. The Canadian Food Inspection Agency (CFIA), which approves the use of these traits, has noticed that compliance with the refuge requirements is slipping, says Schaafsma. The CFIA has the authority to audit growers' seed purchases and also to conduct on-site inspections. The CFIA has the authority to withdraw a seed company's permit to sell a product. Seed companies, in turn, can refuse to sell a technology to growers who repeatedly fail to plant the proper amount of a refuge variety along with their Bt seed.

The amount of refuge required is specified with a particular corn seed. Whether 20 per cent or five per cent of a field must be dedicated to a refuge non-traited hybrid depends upon the science behind the probabilities of insect resistance developing, Schaafsma explains. That, in turn, depends upon the insect or insects being targeted and whether there are one or two separate traits for each insect. Insects are more likely to become resistant to a single trait than to two traits, hence the larger amount of refuge required with a hybrid with only one trait.

Schaafsma points out that the Bt proteins in a corn seed targeted against corn borer have no effect against corn rootworm. The refuge question "is very complex," he adds. "The seed companies know how serious this is."

Just two years ago, the newest development in corn hybrids was Smartstax, a collection of eight traits conferring weed spray tolerance and above and below ground insect control. In 2012, that technology will be available to farmers mixed into a single bag with a non-Bt refuge variety.

The non-traited seeds are located throughout the field. With no need for a specific refuge, the planter operator can just plant corn without worrying about changing seed from field to field or calculating refuge acres.

Monsanto calls its trait and refuge package "refuge in a bag." Dow calls its package "refuge advance" and both companies license their traits to other seed corn companies.
According to Canadian Corn Pest Coalition surveys, more Ontario growers are planting Bt corn – 97 per cent of growers surveyed in 2009 compared to 68 per cent in 2007 and 63 per cent in 2005.

Bt corn as a per cent of total acres has had its ups and downs. Acreage increased to 64.9 per cent of corn acres in 2007 from 57.8 per cent of acres in 2005, and then fell to 62 per cent of acres in 2009. That's all in the face of a widely varying acreage. Ontario corn producers grew 1.88 million acres in 2005, 2.415 million acres in 2007 and 2.125 million acres in 2009. BF