NDSU Extension Service - Williams County

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Scab - July 20, 2016

County Agent Update

Danielle Steinhoff

 

Last week I talked about a fungus called Fusarium Head Blights, also known as scab. But along with scab, another problem that is showing up in Williams County and surrounding areas is wheat midge. Wheat midge as an adult is an orange-colored, fragile, very small insect approximately half the size of a mosquito. Wheat midge has three pairs of long legs, a pair of oval wings, transparent and fringed with fine hairs. Two eye are conspicuous and black. The eggs are elongated, whitish and very small. The eggs are laid on the external surfaces of the developing wheat spikes. The larvae are orange and about 2 to 3 mm long when fully grown. The larvae can be found on the developing seed kernels for two to three weeks, when mature they drop into the soil and burrow down and create cocoons which they can survive in for 10 years or more. Mated wheat midge females lay their eggs underneath the glumes or the palea in florets of wheat heads between the period of heading and early flowering. Therefore fields fields should be monitored from the time when wheat heads start to emerge from the boot leaf until a few days after anthers are visible. It is important to do field monitoring after 8:30p.m. because that is when wheat midge females are the most active. Some methods for detecting adult midge are plate traps, emergence traps, yellow sticky traps and sex pheromone traps. Monitoring fields sometimes is a timely practice, but whether it is nightly or using traps but can present extreme damage that can be caused. Wheat midge is a seed feeder and infests a wheat plant during heading through early flowering. Crop injury can only be caused by larvae, the midge larvae crawl down to feed on the developing wheat kernel.  The wheat kernel will shrivel, crack and become deformed, those kernels could be entirely aborted. Cultural, biological and chemical control methods can be used for controlling wheat midge on wheat. Cultural methods; early planting is the most useful cultural control method, this method is suitable only for hard red spring wheat as durum varieties are later maturing. By planting early maturing wheat varieties, wheat midge infestation is minimized because the crop heads and flowers before peak emergence.  Crop rotation, continuous wheat cropping show be avoided. Continuous wheat cropping encourages the wheat midge population to build up by being able to survive in the soil. Planting crops that are not susceptible to wheat midge such as soybean, sunflower, flax, pea, lentil, chickpea, oat or corn, will reduce the reproductive opportunities for wheat midge. For this and more information look at the Integrated Pest Management of the Wheat Midge in North Dakota (E1330) publication put out by North Dakota State University Extension Service. This article was written by Janet Knodel, Extension Entomologist and associate professor.

 

 

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