By Andi Anderson
Researchers at Iowa State University are combining math and entomology to develop new ways to predict and mitigate soybean aphid outbreaks. The project is funded by a $552,890 grant from the U.S. Department of Agriculture.
The researchers will compare the effect of different water stress levels on the reproductive success of aphids that are either resistant or susceptible to natural plant defenses. They will also evaluate how water-stressed soybeans impact aphid interactions with a parasitoid wasp, which is a natural predator of aphids. Additionally, the researchers will track changes in the ratio of aphids that are resistant or susceptible to natural plant defenses under different water stress scenarios.
The researchers will use this data to develop mathematical models to simulate changes in aphid population dynamics over the course of an entire growing season and in response to a wider array of stressors. This information could help experts predict future pest outbreaks and develop new mitigation strategies for farmers.
The researchers believe that their new model can capture multiple population peaks and will continue improving and expanding it to include more factors, such as plant host suitability, which changes across a growing season, and the effects of drought and flooding.
Soybean aphids can cause severe damage to plants, reducing pod set, seed size, and plant height, resulting in yield losses as great as 40% in the Midwest. Part of the aphid's success is the speed at which they reproduce, both sexually and asexually. On soybeans, aphids can spawn up to 15 generations. They also have the ability to sprout wings and fly to other sources of food or common buckthorn, their overwintering host plant.
In response, farmers can grow aphid-resistant varieties of soybeans, but the emergence of "virulent" aphids threatens this strategy. Virulent aphids withstand the plant's chemical defenses, passing their traits on to offspring.
In 2022, the researchers published a paper exploring the dynamics between virulent soybean aphids and "avirulent" aphids, which are not resistant to new soybean varieties. They found that virulent and avirulent aphids can coexist on a resistant soybean plant. Virulent aphids alter the host plant's chemistry, making it more hospitable to "avirulent" aphids.
The researchers believe that the coexistence of virulent and avirulent aphids is one of the reasons why soybean aphid outbreaks can be so difficult to control. They are also interested in studying predator-based bio-controls with prairie strips between crop fields. With this arrangement, beetles, parasitoid wasps, and other insects that eat aphids can move between two habitats or "patches": the prairie strip and the seasonal crop fields. The researchers believe that this concept could be a promising way to control soybean aphid outbreaks in the future.
Photo Credit: gettyimages-gilaxia
Categories: Iowa, Crops, Soybeans