While Western Canada wheat midge surveys show pest
populations will likely be lower again in 2010 than they have been in the past couple years, wheat growers do have access to three very good midge-resistant spring wheat varieties this year.
The wheat midge survey doesn’t tell the whole story, however, say prairie provincial entomologists. Pest populations appear to be down based on counts made last fall, however, if moisture and timing of crop development this spring are ideal there could be regional and even field-specific flare ups of the pest.
So what are the options? If you are growing wheat, consider growing one of the three new midge-resistant varieties, available for the first time in 2010 (a fourth will be available in 2011 and more are coming along). The new varieties are: AC Unity VB from SeCan, AC Goodeve VB from a new company Alliance Seed Corporation (both are CWRS), and AC Glencross VB an extra-strong wheat variety, from Faurshou Farms Ltd. of Portage La Prairie, Man.
If you don’t grow one of the midge-resistant varieties, be prepared to monitor fields closely. Depending on the crop you are growing — a utility wheat or a #1 Hard Red Spring wheat or durum — it only takes one adult wheat midge on four to five seed heads (for utility class) or one adult midge on eight to 10 heads (#1 durum) to signal the economic threshold for treating the field with an insecticide.
A NEW STRATEGY
One new feature with these midge-resistant varieties is the way they are packaged and marketed. All three — AC Unity, AC Goodeve and AC Glencross are being sold in a 10 percent blend with other susceptible wheats and all are being sold with a stewardship agreement.
The strategy of marketing these wheats in what is known as the Interspersed Refuge System is to ensure that the resistant feature of the varieties remains effective as long as possible. As most producers know, whether it be an antibiotic or a herbicide or insecticide, the bacteria, weed or insect can, over time, develop resistance.
To reduce the risk of the wheat midge developing resistance to the Sm 1 gene, which makes these varieties resistant, the new wheats are being sold in a 10 per cent blend with susceptible varieties.
AC Unity VB (varietal blend) is being sold with a 10 per cent blend of AC Waskada, AC Goodeve VB is being sold in a blend with AC Intrepid and AC Glencross VB is being sold in a blend with AC Burnside. When AC Fieldstar is available in 2011 it will be sold in a blend with AC Waskada.
The role of the 10 per cent susceptible wheat variety is to give the midge a limited feed source. As Ron DePauw, wheat breeder with Agricutlure Canada in Swift Current, Sask., explains, if a midge tolerant variety were grown as a pure stand, the only midge surviving in the field would carry a mutation that allows survival despite the presence of the Sm 1 gene. The virulent midge would mate with other virulent midge and quickly build up a large virulent population.
With a blend of 90 per cent midge tolerant variety and a 10 per cent susceptible variety, the non-virulent midge will survive on the 10 per cent susceptible plants and inter-mate with any virulent midge. The progeny of this cross will be non-virulent.
Along with the blending, these wheats are also being sold with a stewardship agreement to be signed by producers. This means producers have to agree to only grow farmed-saved common seed from this crop for one year, before they have to buy certified seed again. For example, they buy certified AC Unity VB seed for 2010, can save common seed from this field for 2011, but in 2012 they will have to buy certified seed again.
The purpose of the agreement is not to promote certified seed sales, says Todd Hyra of SeCan, but to ensure that the strength of the resistance factor in subsequent crops is maintained. Stephen Fox, plant breeder with Agriculture Canada’s Cereal Research Centre in Winnipeg says a study is underway to determine how long the Sm 1 gene resistance is maintained in subsequent seedings of common seed, but there likely won’t be any preliminary results from that until early 2011.
ALL ABOUT THE VARIETIES
AC Unity VB marketed by SeCan is an excellent hard red spring variety says Todd Hyra. Developed from McKenzie wheat parentage, it is an awned CWRS variety, with high grain yield, improved leaf rust resistance, good resistance to common bunt and very good sprouting resistance. It has maturity equal to AC Barrie and is two to three days earlier than Superb. It comes with a 10 per cent blend of AC Waskada, another awned CWRS variety with grain yield 112 per cent of Barrie and 102 per cent of Superb. It has intermediate leaf rust resistance and good stem rust resistance. Maturity is one day later than AC Barrie.
AC Goodeve VB is marketed by Alliance Seed Corporation, Developed from Intrepid parentage, it is an awnless CWRS, yielding about 108 per cent of AC Barrie. It has resistance to stem rust and loose smut, moderate resistance to leaf rust, but is susceptible to common bunt and very poor resistance to fusarium head blight. It has good protein, very early maturity and is shorter than AC Barrie. AC Goodeve will have a 10 per cent blend of AC Intrepid, an excellent yielding, early maturing Hard Red Spring wheat with strong straw, large kernels and good resistance to stem rust, leaf rust, bunt and loose smut.
AC Glencross VB, marketed through an IP system by Faurschou Farms Ltd. of Portage La Prairie, is probably one of the last extra-strong varieties to be released by the Cereal Research Centre, as the extra-strong wheat breeding program has been cancelled. It is an early maturing, high protein variety, earlier than Glenlea and slightly shorter than Glenlea. It has good leaf rust resistance, and fusarium head blight resistance comparable to Glenlea. The trade off for the higher protein content is slightly weaker straw strength. AC Glencross is being blended with AC Burnside, which has higher yields than Bluesky, but similar to Glenlea. Burnside has up to moderate resistance to leaf and stem rust and is resistant to loose smut.
Lee Hart is a field editor for Grainews in Calgary, Contact him at 403-592-1964 or by email at [email protected]