Research Accomplishment Reports 2011

Biology, Impact, and Management of Soybean Insect Pests in Soybean Production Systems

K.V. Yeargan
Department of Entomology

 

Non-Technical Summary

The ability to predict SBA outbreaks reduces risk to growers, allowing decisions to be made in advance of the field season. Such decisions include variety, insecticide and equipment purchases, and crop insurance protection, not only for soybean growers, but also for vegetable growers impacted by aphid-transmitted viruses. Risk reduction allows growers to better allocate resources and in the end to save money.

Success in classical biological control will reduce populations of, and yield loss from, SBA. A partial success could save producers tens of millions of dollars in control costs alone, with societal benefits of reduced human exposure, reduced non-target impacts from pesticide use, and slower formation of insecticide resistance. A better understanding of North American natural enemies and their conservation will have similar impacts as a partial success in importation biological control.

2011 Project Description

We collected naturally laid stink bug egg masses from soybean plants, including masses from which stink bugs or parasitoids had already emerged (a small fraction of the total masses collected) and those from which they had not. These egg masses were returned to the laboratory and held at room temperature to allow emergence of stink bug nymphs or parasitoids from the intact eggs. The collected egg masses were overwhelmingly (more than 95%) one species, Acrosternum hilare (the green stink bug), with the few exceptions being eggs of brown stink bugs (Euschistus species). Parasitism rates were extremely low (less than 2%).

Approximately three decades earlier, at the same location near Lexington KY, naturally oviposited egg masses of Acrosternum hilare on soybean plants were found to be parasitized at a rate of approximately 45%. In both the earlier study and the 2011 study, the only parasitoid species recovered was Telenomus podisi. No insecticides were used at this site in the earlier study or in 2011, and the reason for the low rate of parasitism in 2011 is unknown.

2011 Impact

This study was done because a highly destructive exotic species of stink bug was recently found in Kentucky, namely the brown marmorated stink bug. This exotic species has caused severe damage to many crops, including soybeans, along the Atlantic Coast of the USA but it has not yet caused problems in Kentucky, probably because of its recent arrival (first detected in Kentucky in autumn 2010).

We anticipate that populations of the brown marmorated stink bug will increase in Kentucky over the coming years, as they have done along the Atlantic Coast. We wished to obtain updated estimates of egg parasitism of our native stink bug species prior to the widespread invasion of Kentucky soybeans by this exotic species. Because of the surprisingly low rates of parasitism found in 2011, we plan to repeat this study in 2012.