NOVEMBER 2018 GERMINATION.CA 51 cycle begins again. Only three or four larvae on a single floret are enough to cause significant damage to wheat spikes but we have seen up to 30 feeding at any point of time on a single developing grain. There may not be any grain left on a spike if the infestation is severe. REMEMBER! There is an insect similar to wheat midge called the Lauxanid that should not be confused with wheat midge. The Launxanid is bigger than the wheat midge and is yellowish-brown compared to the predominantly orange colour of the midge. Lauxanid should not be confused with wheat midge. Photo: Judy Gallagher Midge Tolerant Wheat — A Great Weapon in the War Against Wheat Midge Most wheat varieties are currently suscep- tible to wheat midge, but several midge tolerant varieties of wheat are currently available. Midge tolerant wheat varieties contain a gene called Sm1 (which gets its moniker from the wheat midge’s scientific name Sitodiplosis mosellana). This gene causes the plant to create wheat kernels that contain a phenolic compound that the wheat midge doesn’t care for. After taking an initial bite, the wheat midge will refrain from eating any more of the wheat. This is why it’s called midge tolerant and not midge resistant wheat, since the midge must still do some initial feeding before developing a distaste for the wheat. The Sm1 gene can become ineffective over a relatively short period of time if selection pressure allows the midge popu- lations to 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. An interspersed refuge system requires planting a varietal blend which consists of mostly a midge tolerant variety (90 per cent) with the remaining 10 per cent consisting of a midge susceptible variety. This ensures the refuge is evenly distributed (inter-seeded) throughout the field. The objective is to prevent a buildup of naturally occurring virulent midge — midge that are able to attack plants with the Sm1 gene, thereby dramatically prolonging the viability of the Sm1 gene.