Wheat Straw Turns into Pest Control Delivery System for Great Plains Farmers

Wheat farmers in parts of the Great Plains have been battling a major pest, the wheat stem sawfly, which costs them about $350 million every year. The US Department of Agriculture's Agricultural Research Service (ARS) estimates that this pest has caused significant damage to dryland winter wheat crops in Colorado and Nebraska. Researchers from ARS and their university colleagues have developed a new approach to control the sawfly population by using baled wheat straw as a delivery system for biological pest control.

The idea is to transport Bracon parasitoids, which are natural enemies of the wheat stem sawfly, into areas where farmers need them most. The researchers first identified areas where Bracon populations were established and then harvested wheat straw, baled it, and transported the bales to infested wheat-growing areas in Nebraska and Colorado. At the ARS field station, nine straw bales produced roughly 67,500 parasitoids.

The study found that swathing, baling, transporting, and spreading wheat straw can be a viable means of introducing Bracon into new habitats for the biological control of wheat stem sawfly in wheat production. The researchers also observed higher parasitism at field edges than farther inside the fields, which suggests that the goal is not simply to release insects but to establish a population capable of attacking the pest in the wheat landscape.