Development and validation of node-based sample units for estimating soybean aphid (Hemiptera: Aphididae) densities...

Area of Science:

• Agricultural Entomology
• Pest Management
• Soybean Production

Background:

• Soybean aphid (Aphis glycines) is a major pest of soybean (Glycine max) in the North Central United States.
• Field cage studies are crucial for evaluating control strategies but are limited by high aphid densities.
• Estimating whole-plant aphid density from reduced sampling is needed to overcome experimental constraints.

Purpose of the Study:

• To adapt and validate a node-sampling method for estimating soybean aphid populations within field cages.
• To determine if existing open-field parameters are suitable for caged aphid population estimation.
• To develop an efficient sampling strategy that increases the number of treatments and replicates in cage studies.

Main Methods:

• Extended the node-sampling technique to caged soybean aphid populations.
• Utilized four independent data sets of caged populations for cross-validation.
• Compared node-sampling estimates with whole-plant counts in statistical analyses.

Main Results:

• Parameters from open-field conditions were found inappropriate for caged populations.
• A three-node sampling unit with a weighted formula provided accurate and robust estimates of whole-plant aphid density.
• The node-sampling method reduced aphid counts by an average of 60%, with greater reductions at higher densities.
• Statistical analyses yielded nearly identical results using either whole-plant or node-sampling estimates.

Conclusions:

• The developed three-node sampling method is an efficient and accurate tool for estimating soybean aphid density in field cages.
• This method significantly reduces counting effort without compromising statistical power.
• The improved efficiency allows for more extensive research, facilitating better soybean aphid management strategies.