Extension and research to facilitate the incorporation of soybean-aphid resistant varieties into Iowa crop production

Two projects are being undertaken to provide data on the host-plant resistance of several varieties of soybeans to soybean pests within the state of Iowa. One project studied five demonstration plots planted in May of 2010 to determine the effect of resistant soybeans on soybean aphids and other foliovores. Each plot involves six different treatment using three types of soybean varieties: susceptible, organic, and soybeans containing the Rag-1 gene. Each plot was counted every two weeks to determine levels of aphid and foliovore infestation. When a threshold of 250 aphids per plants was reached, certain plots received a treatment of insecticide. Each plot was maintained according to normal agronomic practices, and each plot was harvested to determine the yield. Concurrent with the demonstration plot project, several varieties were grown in a research plot and greenhouse for testing against several insect foliovores of soybeans. The purpose of this testing was to establish whether or not soybeans with a known resistance to aphid had any ability to resist attack by insect foliovores other than soybean aphids. Nine varieties where used for testing: 3 varieties containing the Rag-1 gene and their respective near-isolines, and 3 varieties with a known resistance to Japanese beetle and Mexican bean beetle. Once the soybeans began to bear trifoliate leaves, each insect was tested using a choice and a no-choice test comparing different resistant varieties by taking measurements of how much the insect was consuming, mortality, and what preferences the insect displayed during feeding.