Procedures Developed to Identify Aphids Infected with Barley Yellow Dwarf
By Mary Lou Peter Kansas State University Research and Extension
MANHATTAN - A team of researchers, extension specialists and agents at Kansas State University is working with wheat producers to determine what percent of the aphid populations in Kansas have the potential to transmit yield-robbing barley yellow dwarf (BYD) into Kansas wheat. The project is a step toward better understanding and ultimately improving management options for BYD.
"Every spring when the BYD symptoms start to show up, there is always concern around the state that there is more of the disease than expected despite that we never saw plants covered with aphids," said Jeff Whitworth, K-State Research and Extension entomologist. "However, it only takes one infected aphid to infect one or possibly more plants."
Barley yellow dwarf can cause serious problems in wheat, including death, especially if young plants are infected in the fall. As part of the three-year project, which began in 2012, the team has already developed procedures to collect live aphids in wheat fields and transport and test to detect BYD in the aphids. Through their saliva, aphids serve as vectors of the BYD virus. Collecting and transporting the aphids live is important, Whitworth said, because the virus degrades too much to be detected in dead aphids. He, along with K-State entomology professor and team leader Mike Smith and a group of entomologists, agronomists, plant pathologists, extension agents, is working on the project, which was funded by the Kansas Wheat Commission. Many species of aphids may vector BYD, but in Kansas, Whitworth said, it is most commonly attributed to bird cherry-oat aphids or greenbugs, the two most common wheat aphids in the state. Both over-summer in grasses including corn, sorghum, and volunteer wheat, and also migrate into the state from southern states in fall, late winter, and spring. "These aphids suck juice from plants and, under stressful growing conditions, can be detrimental just due to their feeding," he said. "However, this is rare in Kansas, because lady beetles and parasitic wasps usually control aphid populations before they stress wheat plants. Aphid problems come mainly from their ability to transmit BYD, and it only takes one infected aphid to transmit BYD to the plant." Aphids become infected with the virus by feeding on an infected plant. Once the aphid is infected, it becomes a carrier and can potentially infect other plants that it feeds on. Infected plants then become the reservoir and other aphids feeding on those plants can become infected. The team developed a map http://www.flickr.com/photos/ksrecomm/9665228616/ that reflects the initial sampling of wheat fields in the spring of 2013. Sample sizes varied, from 10 to many aphids. While it's too soon to draw conclusions from the project, the team is putting together information that will be educational to growers and researchers alike about aphids and barley yellow dwarf in Kansas, Whitworth said. The next step is to work with growers around the state regarding submitting samples of live aphids once wheat fields have been established enough to attract them. More information about that will come out this fall.