By TIM THORNBERRY
Kentucky Correspondent

LEXINGTON, Ky. — In today’s economy, every penny counts when it comes to production costs for any farmer. But with more consumer awareness of what goes into commodities, there is a heightened awareness of using chemicals such as pesticides, as well.

A new study at the University of Kentucky (UK) is taking a look at ways to rid winter wheat of pests in a natural way. UK doctoral student Katelyn Kowles and her advisor, James Harwood, an assistant professor in the UK Department of Entomology, are studying the structure of food webs in winter wheat to ultimately see if natural predator insects and spiders can effectively control pest populations.

“As we try to build sustainable crop systems, understanding predator/prey relationships is crucial,” Harwood said. “We’re looking at using natural enemies such as spiders, beetles and ladybugs that are already out there and encourage their populations in wheat production systems, and make sound management decisions to growers who could reduce the necessity of chemical inputs into their wheat.”

The study is focusing on such pests as slugs and a variety of aphid species, including English grain aphids and bird cherry-oat aphids. According to information from UK, these aphids are carriers of the barley yellow dwarf virus, the most widespread and destructive virus of wheat.

The virus causes an estimated 17 percent loss in world wheat production annually and in Kentucky, the damage can vary from year to year with epidemic years seeing millions in economic losses.

There is no doubt that the use of chemicals to control pests and improve yields has saved farmers countless dollars over the years, but environmental concerns have made researchers look at new alternatives.  Important to this study is the use of predators already present in the local ecosystem.

“The question is, how can we enhance their underlying populations? The key to using them is having them present when the pests first start reproducing,” said Harwood. “Because these predators feed on not just the pest but everything else that is out there, they can sustain themselves very early in the year, so once the pests do start colonizing the wheat systems, the predators are already there and can ultimately feed on them right away.”

Harwood added if low populations of these insects can be knocked out early in the season using natural predators for biological control, yield losses can be minimized and hopefully the research will generate sufficient data to aid growers and commodity groups to make sound, sustainable management decisions.

Kowles serves as the right-hand person on the research, so to speak, and knew upon hearing of the project that UK was the place for her doctoral studies.

“I just got here in August and did some initial sampling last fall just to see what insects we had out there,” she said, speaking of a 4.5-acre research plot. “Hopefully, come the end of March or early April, I’ll be able to get out there and do some experiments.”

Part of that research involves looking inside the predators to see exactly what they are eating. Through a process called gut content analysis, the contents of a predator’s digestive tract is gathered and DNA of prey is analyzed. This data, according to the research team, provides information not only about the prey and the predator, but a predator’s foraging preferences and how an abundance or limited number of prey alters the structure of the food web.

“Through techniques that amplify the DNA, we separate all the individual prey items’ DNA from the guts, then we can sequence that and figure out what the (predator) ate last,” said Kowles.
She also said once the team finds just what pests the predators eat, they can do things to manipulate the habitat to increase the beneficial insects.

“It’s conservation, biological control. We want to reduce the use of pesticides and create a more sustainable agricultural system,” she said. “So by having these low-input, low-cost habitat manipulations, we can increase these beneficial natural enemies at a low cost to farmers.”

While biological control of insects has been around for hundreds of years, it is becoming increasing popular now as the effects of pesticides becomes more evident, added Kowles. This particular study is focusing on winter wheat, but the premise of the research can also be used on other crops.

“What we have found elsewhere is these predators, as soon as we see pests arriving, feed at what is a very disproportionally high rate, potentially limiting (the pest’s) population growth,” said Harwood. “We’ve demonstrated that in winter wheat production systems in Britain and we’ve also shown that to be the case in soybean systems in North America.”

Another crucial point of the research in a management-based approach is to find a way to grow the habitat of these predators in ways that farmers would adopt.

“In winter wheat, because of the value of the crop, you cannot plant, say, high-cost wildflower strips, which encourages all of these predators,” said Harwood. “But you potentially leave areas with minor amounts of weed growth. The field margins for example, around the fields, if you leave those to grow up with a high density of weeds, those can sustain predator populations early in the year.”
The researchers presented their study to wheat growers and industry professionals during the 2010 UK Winter Wheat Meeting.