Database Research SummariesEffect of Incremental Sub-Threshold Levels of Insect Defoliation on Yield of Soybeans in Mississippi
Research Focus
The focus of this project is to refine treatment recommendations by evaluating the effects of multiple defoliation events on soybean yield loss and how soybean planting date can further affect yield loss associated with defoliation of Mississippi soybeans.
Objectives
- Evaluate the effects of compounding defoliation on vegetative soybeans.
- Evaluate compounding defoliation on vegetative and reproductive stage soybeans.
- Evaluate the effects of planting date on defoliation.
Results
- Both irrigated and non-irrigated locations did not yield lower than the check when defoliated 33 or 66%. Yield loss did occur, however, once defoliation levels reached 100% at V3 and V6 growth stages, and were independent of each other.
- Continuous defoliation at any level throughout the vegetative stage did not reduce yields significantly below the untreated control. Defoliation levels of 66 and 100% at R3 reduced yields below the check. Defoliation levels of 33 and 66% occurring season-long reduced yields below the untreated check as well. These results indicate that defoliation occurring prior to the R3 growth stage has very little, if any, additional impact on reproductive defoliation yield losses.
- The Starkville tests in 2015 and 2016 displayed trends that later-planted soybeans were more susceptible to yield loss from defoliation than earlier-planted beans. Soybeans planted mid-season suffered slightly less yield loss than the earliest and latest planting dates, with the exception of the mid-June planting date in 2016.
Importance
- These tests could help producers by creating a variable threshold based on planting date or defoliation that occurred during previous growth stages.
For more information about this research project, please visit the National Soybean Checkoff Research Database.
Funded in part by the soybean checkoff.
