Midge Tolerant Wheat Retailer Training Module 1 Midge Tolerant Wheat Technology
Presentation Overview • Orange Wheat Blossom Midge • Life Cycle • Midge Damage • Midge Tolerant Wheat • Varieties • How it Works • Single Gene Resistance • Interspersed Refuge System
Wheat Midge Life Cycle • The orange wheat blossom midge has 4 stages: • Adult – Adult flies emerge in late June/early July, mate and females lay eggs on newly emerged wheat heads during warm, calm evenings. Emergence peaks mid-July.
Wheat Midge Life Cycle • Eggs – Eggs are laid, either singly or in clusters of 3-4 eggs, on the wheat heads. This stage lasts 4-7 days. • Larvae – Upon hatching, the larvae move into the florets to feed on the developing kernels for 2-3 weeks. Then they crawl off the wheat head and over-winter in the soil. • Pupae – Once temperature and soil conditions end the over-wintering period, larvae move to the soil surface to pupate. Emergence of adult flies begins in late June/early July and can continue for up to 6 weeks.
Midge Damage • Crop damage occurs when midge larvae feed on the developing wheat kernel, causing them to shrivel, become deformed or completely abort. • Damaged kernels cause downgrading in wheat samples. • Crop yields are also reduced as 40-50% of damaged kernels are blown out of the combine during harvest.
Midge Tolerant Wheat Varieties • Several spring wheat varieties were developed by Canadian wheat breeders at AAFC in Winnipeg & Swift Current, and the Crop Development Centre at the University of Saskatchewan. • Funding for these projects comes from government, the WGRF check-off program and variety distributors. • All these new varieties contain the single gene (Sm1) which provides midge tolerance. • Sm1 was moved into spring wheat using traditional plant breeding techniques.
Benefits of Midge Tolerant Wheat • Prevent an estimated $36 per acre* loss from midge damage downgrading and yield reductions. • *Based on the economic threshold of one midge per 4 to 5 wheat at flowering = estimated 15% yield loss if not controlled. Higher midge levels can lead to greater losses. 15% x $6/bu wheat x 40 bu/acre = $36 • Reduce reliance on insecticides, the traditional method of midge control. • Gain more flexibility in crop rotations and seeding dates.
How it Works • When the insect begins to feed on the seed, the Sm1 gene causes the level of phenolic compounds (naturally occuring acids in wheat kernels) to elevate more rapidly than in wheat kernels without the Sm1 gene. • The higher levels of phenolic acids cause the midge larvae to stop feeding and starve to death.
Single Gene Resistance • Midge tolerance is based on a single gene (Sm1) that can become ineffective over a relatively short period of time as insect populations change. • An interspersed refuge system is required to extend the life of midge tolerance from as little as 10 years to 90 years or longer.
Interspersed Refuge System • Requires planting a varietal blend (VB) which contains 90% midge tolerant variety and 10% midge susceptible variety. • Ensures the refuge is evenly distributed (inter-seeded) throughout the field. • Objective is to prevent a build-up of naturally occurring virulent midge – midge that are able to attack plants with the Sm1 gene.
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