The Orange Wheat Blossom Midge is becoming more of a problem for Montana's wheat growers. With education and vigilance you can minimize the damage from this wheat pest.
1. Life cycle- There is only one generation per year. The larvae overwinter in the soil and emerge in May with moist soil conditions. The larvae then returns to the soil to pupate and will re-emerge as adults with peak emergence around the first of July. They will lay eggs on the wheat head florets. The larvae will hatch and feed on the seed heads for 3 weeks and return to the soil. They can stay dormant in the soil cocoon for 5-15 years.
2. Host plants- Spring wheat and durum wheat are the principle hosts. Other host plants include spring triticale, rye, intermediate wheatgrass, bluebunch wheat and quack grass. Barley can be a secondary host as can winter wheat which is the least damaged because of heading dates.
3. Treatment options- Plant earlier heading varieties of wheat as soon as possible and minimize late tillering by using higher seeding rates. If plants are 80% flowered by the time adults emerge the first week in July do not treat with insecticide. This will preserve a small parasitic wasp that will control 25-40% of the midge population. If the crop will not be past flowering at this critical time put out traps and check every other day. Scouting is best done at dusk in warm, calm and humid conditions. They will not fly if the wind is 5mph or stronger or if the temperature is under 60*. Treat at 70% head emergence if you find 1 midge per 7-8 heads. Insecticide treatments at this time have shown to have approximately 75% control and double the yields over check fields.
4. Damage- Orange wheat blossom wheat midge causes a 30-50% reduction in seed size and also causes a reduction in falling numbers. The larvae converts starch into food. A side effect of this is an increase in protein. In 2008 areas with significant untreated wheat midge pressure were docked on average $1 per bu. with an average protein of 17%. Dockage came from decrease in falling numbers and an increase in sprout, mold, and misdiagnosed frost damage.
5. Prevention- Crop rotation into peas, lentils, canola, safflower and alfalfa have all been effective. There is also a gene identified called Sm1 that causes the seed to produce a compound that causes larvae mortality when eaten. This will most likely be blended with a susceptible variety for planting to increase the gene viability from 10 years (no blending) to 90 years (with blending).
There are many prevention and control options for this insect to minimize damage to spring wheats. If you have any questions about this or other small grain pests please call us. We have 3 Certified Crop Advisors on staff that are happy to help you manage your land and crops.