The Pest

Photo of a wheat midgeWheat Midge Life Cycle

The orange wheat blossom midge is well known across most of western Canada. The life cycle of the wheat midge has four stages:

  1. Adult – The adult midge is a very small, fragile orange fly about half the size of a mosquito, approximately 2 to 3mm 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.

    In late June or early July, midge begin to emerge from the soil as adult flies, mate, and the females lay eggs on the newly emerged wheat heads. Midge emergence peaks in mid-July. Female midge, which live for less than seven days, lay an average of 80 eggs. 
     
  2. 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 wheat heads. The egg stage lasts four to seven days, depending on environmental conditions, especially temperature.
     
  3. Larvae – Upon hatching, the small orange larvae move from the spikelet surfaces into the florets to feed on the developing kernels. Larvae feed and develop for two to three weeks, growing to 2 to 3 mm in length, before crawling off the wheat head to find their way to the ground and bury themselves in the soil. Over-wintering larvae may remain dormant until conditions are favourable for development, whether that is the following spring or several years later.
     
  4. Pupae – Once temperature and soil conditions end the over-wintering period, the larvae become active and move to the soil surface to pupate. Emergence of the adult flies begins in late June or early July and can continue for up to six weeks.