Lurking just beneath the soil, there may be a wheat midge army poised to wreak havoc this growing season. While wheat midge (Sitodiplosis mosellana), doesn’t regularly pose a substantial threat in Alberta, the 2011 forecast is out and it predicts that before long, the midge will be too.
This year, farmers may experience heavy infestations in areas east and south of Calgary. As well, widespread infestation is expected throughout much of the grain-producing part of the province, with moderate infestation spots near Lloydminster, Edmonton and Medicine Hat.
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The wheat midge is a small, winged insect, and as an adult, is approximately half as small as a mosquito. However, it is when the insect reaches the larval stage that it causes the most damage. The life cycle begins when a mature female lays her eggs in newly emerged wheat heads. The eggs will begin to hatch between four and seven days after they have been laid, at which point the larvae move to feed on the wheat kernels. After two or three weeks, they stop feeding and bury themselves in up to four inches of soil to pupate, usually emerging in the spring when conditions are right.
However, the reason the wheat midge can pose such a threat to crops is because if conditions aren’t wet enough, they can remain in the soil for several years – and the spring of 2011 is predicted to be wetter than average. Sometimes, the midge will consume entire kernels, reducing yields and often, kernels are fed on and left damaged, which affects the grade of the crop.
Refuge system
There are currently two midge-tolerant wheat varieties available, but they require responsible use – which means limiting the use of farm-saved seed to one generation past certified seed. The Midge Tolerant Wheat Stewardship Team – a partnership between several industry groups representing plant breeders, government, seed growers, seed distributors and producer groups – is reminding producers not only that midge-tolerant varieties are available, but also of why they need to be protected.
The varieties became commercially available in 2010 after 15 years of research. The Sm1 gene was moved into spring wheat varieties. When the midge begin to feed on the kernels, the gene causes the kernel to release more acids than it ordinarily would. The acids cause the larvae to cease feeding and as a result, the pest starves.
Producers using the midge-tolerant varieties are required to sign a stewardship agreement, limiting the use of farm-saved seed. The varieties use a “refuge system,” which means 90 per cent of the seed is wheat midge tolerant and 10 per cent is not. Both types of seed are fully interspersed throughout the crop and as a result, the wheat midge is exposed to enough of the ordinary variety to resist developing a mutation to the Sm1 gene. There is a very low level of naturally gene-resistant midges, but the trait is recessive. By providing a refuge of untreated seed within the tolerant variety, the wheat midge’s susceptibility to the tolerant variety will remain the insect’s dominant trait.
Markert Seeds Ltd. at Vulcan is growing AC Unity VB, which is distributed by SeCan and hit the market for the first time in 2010. While Ron Markert says lack of awareness of the new seed may have dampened its sales, those who did take advantage of it were pleased by its performance.
“The thing about this Unity is that it is an excellent yielder, and I don’t think people caught on to that aspect of it,” Markert said, adding that Seed. ab.ca rated the variety at 107 per cent of check. “It’s not the highest, but it’s in the upper end. We’ve grown it and we’re very happy with the yields you get from it.”
Dale Alderson, general manager of Alliance Seed Corporation, distributor of AC Goodeve VB, says the variety performs well, stands up well and also succeeded in reducing maturing time.
“The genetic resistance to wheat midge is the same in all varieties – it’s a single gene resistance to wheat midge – so if you have it, you’ve got resistance, and this one has it.”
SeCan and Alliance distribute the varieties currently available, and there are others in development. More information can be found at www.midgetolerantwheat.ca.
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“…it’sasinglegeneresistancetowheatmidge–soifyouhaveit,you’vegotresistance,andthisonehasit.”
DALE ALDERSON
ALLIANCE SEED
