Page Banner

United States Department of Agriculture

Agricultural Research Service

Title: Estimating Aphidophagous Coccinellid Populations in Alfalfa (Revised 7/31/96 to Correct Authors Listing)

Authors
item Elliott, Norman
item Michels, Gerald - TEXAS A&M UNIVERSITY

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 30, 1996
Publication Date: N/A

Interpretive Summary: Coccinellids (ladybird beetles) are important predators of aphid pests, such as the pea aphid and spotted alfalfa aphid, in alfalfa. Sampling methods for coccinellids would be useful for integrated pest management (IPM) decision-making in alfalfa. We tested several sampling methods to determine those best suited for sampling adult and immature (larval) coccinellids in alfalfa. Based on ease of use, the time required for sampling, and the resulting accuracy of estimates of population density, sweepnet sampling was considered to be the best sampling method. Other methods (removal sampling, quadrat sampling, and visual counting while walking through a field) were either less accurate or took considerably more time. Our results may aid in development of IPM systems that rely more heavily on biological control than on use of chemical insecticides.

Technical Abstract: Coccinellids are important predators of aphids in alfalfa. Precise, yet time-efficient sampling methods for coccinellids would be useful in integrated pest management (IPM) research and decision-making in alfalfa. We compared removal with quadrat sampling to determine if removal sampling provided useful estimates of absolute population density of adult and larval coccinellids in alfalfa. We also determined the utility of timed count and sweepnet sampling for estimating adult and larval coccinellid densities. Quadrat and removal sampling were found to be equally efficient for estimating absolute density, in terms of statistical precision per unit cost (minute of sampling) for adult coccinellids, while removal sampling was more efficient that quadrat sampling for larvae. However, removal sampling provided biased estimates of population density for adults and larvae of some species. Regression models were developed to convert estimates of relative density obtained by sweepnet and timed count samplin to estimates of absolute density (number per m**2) of adult and larval coccinellids. Sweepnet sampling was more efficient than timed counts for estimating the number of adult coccinellids per m**2, while the two methods were equally efficient for estimating larvae density.

Last Modified: 10/22/2014
Footer Content Back to Top of Page