Precision agriculture and soybean insects

The use of precision agriculture to study insect pests is a new area of study, with the first research published just a few years ago. The Iowa Soybean Promotion Board is funding an important soybean integrated pest management project at Iowa State University. The project involves gathering detailed information about insect distribution over large areas.

One benefit of the project is that learning more about how insects are distributed in a field will help us to develop more focused methods for sampling and monitoring crop pests. A second benefit is that as we learn more about insect dispersion in crop fields, we can add to our overall understanding of crop pests, which may lead to more innovative management tactics. Such tactics might include targeted insecticide application or a change in cultural practices that could create unfavorable conditions for the pest. Ultimately, the goals of this project are to find more tactics growers can use for maximizing yield by efficiently managing pests.

One of the most critical soybean pests in Iowa is the bean leaf beetle. Our initial field results from a study that began in 1996 showed no strong patterns in bean leaf beetle distribution in the middle of the season, but a clustered distribution late in the season in the southwest field corner. It is likely that this cluster was large enough to cause economic damage from pod feeding. We also found that where beetles occurred, the soybean plants were shortest. Short plants also grew in areas where soil pH, organic matter, and potassium, calcium, and magnesium levels were high.

In 1997 western and eastern sites were added to the study. At the western location, we detected a high population of ectoparasitic mites on bean leaf beetles. We found the most parasitized beetles where we also found the most bean leaf beetles. The effect of these mites on bean leaf beetles has not been determined, but the more we learn about this relationship the greater the opportunity for biological control.

The potential is great for using precision agriculture to manage insect pests, but there also are hurdles that must be overcome. For example, sampling for pests over an entire field is extremely labor-intensive. The field must be sampled using sweep nets and each sample must be examined individually. During the summer, there's only a short window of opportunity for using the collected data to make management decisions. Most growers won't have the time or resources to collect and process samples from an entire field before making a decision. We hope that by gaining a better understanding of pest distribution, sampling can be targeted and the total number of samples taken can be reduced.

This article originally appeared on pages 4-5 of the IC-480 (4c Precision Ag Edition) -- April 9, 1998 issue.

Updated 04/08/1998 - 1:00pm