By Tom Laurdison
Wheat and barley producers remember about fifteen years ago… when Russian Wheat Aphid (RWA) was about to end cereal grain production in Colorado, New Mexico, and Wyoming. Thankfully, that didn’t happen.
A progression of technologies, beginning with the widespread use of insecticides, followed by RWA tolerant wheat varieties such as Halt seemed to have solved the aphid problem. Of course, barley producers have yet to be assisted by resistant varieties, and non-resistant wheat and barley require treatment with insecticides when infested with RWA.
However, RWA problems seem to be declining lately, and that’s not just an accident. Colorado State University and the USDA Agricultural Research Service have been releasing several insect predators of RWA in Colorado.
Unlike insecticides or tolerant varieties, biocontrol insects should be able to maintain quite a bit of RWA control without help from producers. This is especially good news for barley producers, because multiple treatments of insecticides have been the only effective control of RWA, and the cost of control has made barley production much less economically viable.
In fact, the routine use of insecticide for RWA control could cause the loss of many of the biocontrol bugs that are increasing throughout the state. Because the biocontrol bugs (mostly, but not all, subspecies of “ladybugs”) require a certain level of RWA to live on, producers should limit using insecticides to control low levels of RWA.
In many cases, biocontrol insects can keep the level of RWA below the economic threshold (the point at which the insecticide treatment earns a profit above the cost of chemical and application) of RWA infestation. It just makes sense to keep the good bugs in the field and money in the pocket. If in doubt, ask your extension agent if insecticide treatment is needed before spending on a treatment that may cost you money in the long run.