When scouting soybeans, what is your reaction to the discovery of a colony of soybean aphids? Do you watch and wait? Do you immediately spray the spot or the entire field? Do you know what the recommendations are for threshold levels of aphids that begin to cause economic damage? Instead of putting you on the spot, we’ll find out how your neighbors answered those questions.

Aphids invaded soybean fields early in this century and some years have made a pest of themselves and other years have remained scarce. They seem to be more prevalent in the northern parts of the Cornbelt than in the southern reaches, so a survey team from Minnesota, Iowa, Wisconsin, and Michigan questioned hundreds of soybean farmers in those states to determine their attitudes about controlling soybean aphids with chemical sprays or more natural means, and what the trends indicated from 2004 to 2006. Their analysis indicates producers generally initiate pest control measures based on aphid counts, weather, and plant stages.

In 2004, 13% of farmers treated for aphids and sprayed 50% of their acreage. The following year, 84% sprayed, and 87% of the acreage was treated. In 2006, 35% of farmers sprayed for aphids, and 81% of the acreage was treated. Most farmers had learned about aphids and even in 2004, 81% were aware that once a field was sprayed, soybean aphids could repopulate and cause economic damage. Three out of four farmers were aware that aphids removed sap from soybeans, but the other 25% gave a broad variety of answers of how aphids damage a plant.

Over 75% were aware that profitable treatment frequency depended on aphid counts, weather, and plant stage. The balance believed treatment should be scheduled depending on the month. Less frequent was producer awareness of when soybean plants could be damaged by aphids, the responses were scattered throughout the entire growth range of the soybean plant.

Two-thirds of farmers used 250 aphids per plant as the threshold for treatment, but others provided answers as low as 3 per plant. Scouting reports were considered a valuable tool in decision making and 84% used them for that in 2004, but by 2006, that number had risen to 94%. 54% said plant growth stages were important in the decision, but other decisions to spray were based on the availability of custom applicators and whether neighbors were spraying. Half of the farmers indicated they had adopted most university recommendations for integrated pest management, which includes the use of natural predators to assist in the reduction of aphid pressure on soybeans.

Summary:
Although soybean aphids is a relatively new invasive pest in the Cornbelt, farmers who raise soybeans have quickly learned his potential for damage and are demonstrating growth in their decision-making on how and when to treat any problem fields. While 50% indicated they followed most university IPM recommendations, there were still quite a few farmers whose decisions to spray or not to spray were based on a wide variety of other factors.