The Damage of Wheat Midge
The wheat midge (Sitodiplosis mosellana) is found in most areas around the world, wherever wheat is grown. Significant damage to wheat crops occurs regularly in Alberta, Saskatchewan, Manitoba, southern British Columbia, Minnesota, North Dakota, Montana and Idaho.
Spring wheat varieties are susceptible to wheat midge, but some are more seriously affected than others. Although the midge also attacks other members of the grass family, including barley, couch grass, intermediate wheat grass and rye, infestations on these plants are usually not serious enough to warrant control. Research and breeding into wheat midge resistance conducted at the Cereals Research Centre (Agriculture and Agri-Food Canada – Winnipeg) and the Crop Development Centre (University of Saskatchewan) has provided midge tolerant wheat varieties as an additional tool for the management of this insect pest.
Infestations of wheat midge can reduce crop yields and lower the grade of the harvested grain. Midge may exist at low population levels for several years before becoming a significant problem. But, if conditions become favourable, populations can reach epidemic proportions quickly. Producers inexperienced with wheat midge infestations often mistake the symptoms, and report that frost or drought caused reduced yields or poor quality grain.
Crop damage occurs during the larval stage. The midge larvae, after hatching, feed on the developing wheat kernel, causing it to shrivel, crack and become deformed. As there are no visible, external changes in colour, size or shape of the affected wheat head, the damage to the crop is not readily apparent. Damage can only be detected by inspecting the developing seed within the glumes.
Damage to wheat kernels will vary within a single head.
- Some wheat kernels may be only slightly damaged or not affected at all.
- A few wheat kernels may be aborted entirely.
- Other wheat kernels will not fully develop, and be small and light enough to pass through the combine with the chaff during harvest.
The loss of kernels lowers the yield, whereas damaged kernels will reduce the grade of the harvested wheat. Standards established by the Canadian Grain Commission limit midge damage in No. 1 CWRS and No. 2 CWRS to two per cent and eight per cent respectively, before grade is affected. Damage tolerances for amber durum are two per cent for No. 1 CWAD and eight per cent for No. 2 CWAD. However, if there is disease associated with midge damage, referred to as severe midge damage, grading tolerances are only 0.1 per cent and 0.25 per cent for CWAD No. 1 and No. 2, respectively.
More detailed information regarding grading is available by the Canadian Grain Commission. See the Official Grain Grading Guide, Chapter 4 – Wheat.
Life Cycle and Identification
Adult – The adult midge is a very small, fragile orange fly about half the size of a mosquito, approximately two to three mm long. Two black eyes cover much of its head. The midge has three pairs of legs that are long relative to its body size. Its wings are oval-shaped, transparent and fringed with fine hairs. Adult midge emerge from the pupal stage in late June or early July. During the day, adults remain within the crop canopy where conditions are humid. In the evening, females become active at the top of the wheat canopy, laying eggs on the newly emerged wheat heads. Female midge live for less than seven days and lay an average of 80 eggs.
Eggs – Egg laying generally takes place after 8:30 p.m. when wind speeds are less than 10 km/h and the air temperature is greater than 15°C. Eggs are laid, either singly or in clusters of three or four eggs, on the florets, on the external surface of the glumes or in outer grooves on the florets. The egg stage lasts four to seven days, depending on environmental conditions, especially temperature.
Larvae – Upon hatching, the small orange larvae move from the outer surface into the head to feed on the surface of developing kernels (Figure 2.). Frequently, three to four larvae per floret have been observed, but in severe infestations, there may be as many as 26 larvae feeding on a single kernel.
Larvae feed and develop for two to three weeks, growing two to three mm in length, before dropping off the wheat head in order to bury themselves in the soil. Under dry conditions, larvae will remain in the head and, rather than shedding their last larval skin, will shrink back inside the skin and stop developing. The larvae appear to be enclosed within a transparent envelope and can survive for some time in this protected state. The larvae will become active when moisture conditions improve and may move into the soil. However, the larvae may also remain in the wheat heads until threshed during harvest.
Most larvae remain within the top five cm (two inches) of soil but some may burrow 10 cm (four inches) below the soil surface. The larvae spin round cocoons that are about half the size of a Polish-type canola seed (Figure 4.) Over-wintering larvae may remain dormant until conditions are favourable for development, whether that is the following spring or several years later.
Once temperature and soil conditions end the over-wintering period, the larvae become active and move to the soil surface to pupate. Depending on the conditions, the larvae will pupate with or without a cocoon. Temperature, soil moisture and geographic location will affect emergence of the adult flies, which starts in late June or early July and can continue for up to six weeks.
- 1. Low temperature and high temperature resistant midge, the overwintering mortality rate lower than the summer mortality. Soil moisture conditions are important factors of overwintering larvae began to move, is a necessary condition for pupation and eclosion of midge. Different wheat varieties, different degree damage of wheat midge, general awn length spiny, KouJin spikelet intensive, flowering period is short and neat, peel thickness variety, of adult midge eggs and larvae invade and damage were negative.
UseIT04 mosquito trapto catch wheat midges. One of these new solution developed by QM is called the IT04 outdoor mosquito trap, by using photo catalysis of TIO2( titanium dioxide). When a titanium dioxide surface is irradiated by light, the photo catalytic effect and hydrophilic are activated together. Any organic chemical in contact with the surface will undergo decomposition to CO2 and H2O and thus releasing a smell that attracts female mosquitoes. IT04 mosquito trap is also works for wheat midges.
Comparing the old heavy propane mosquito trap, the IT04 mosquito trap (for outdoor) and the MBOX mosquito trap (for indoor) of QM is more convenient and affordable.The IT04 is combine with solar panel so that it don’t need to lay the wire. QM’s tech is more ecofriendly and increases the chances of catching more female mosquitoes. Besides, you won’t hear a zap anymore when it working. http://mbox-qm.com