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ARS Home » Pacific West Area » Logan, Utah » Pollinating Insect-Biology, Management, Systematics Research » Research » Publications at this Location » Publication #150694
Title: SWEEP SAMPLING TECHNIQUE AFFECTS ESTIMATES OF THE RELATIVE ABUNDANCE AND COMMUNITY COMPOSITION OF GRASSHOPPERS (ORTHOPTERA: ACRIDIDAE)

Author
item O'NEILL, KEVIN - MT UNIV DPT OF ENT
item LARSON, DEANNA - MT UNIV DPT OF ENT
item Kemp, William - Bill

Submitted to: Journal of Agricultural and Urban Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/20/2002
Publication Date: 7/20/2003
Citation: O'Neill, K.M., Larson, D.P., Kemp, W.P. 2003. Sweep sampling technique affects estimates of the relative abundance and community composition of grasshoppers (Orthoptera:Acrididae). Journal of Agric. and Urban Entomology. 19(3):125-131.

Interpretive Summary: Many grasshopper pest management decisions on North American rangelands are based on counts from scouts using sweep nets. We have observed that there can be a great deal of variability in sweep net technique among scouts and we conducted a study to see whether sweep net technique among scouts might influence the estimates of population densities or species composition. Such differences, if real, could impact the decision to employ chemical control measures. In one set of analyses, we varied either the height of the net above the ground, the speed of sampling, or the arc of the sweep. Results indicate that estimates of abundance and community composition derived from sweep samples can vary with relatively minor differences in technique. When we evaluated the effect of having two samplers deliberately mimic each other's technique on close parallel transects, no differences were found among samplers, suggesting that standardization of technique can improve precision.

Technical Abstract: Because sweep sampling is the most commonly used method of estimating grasshopper abundance and community composition on rangeland, it is of interest to evaluate its accuracy and precision. Previous studies have concluded that sweep sampling provides fairly accurate estimates of community composition. However, it is possible that differences among non-standardized sampling techniques result in variable estimates of abundance and species composition among samplers or among different samples taken by the same person. We deliberately varied the sweep sampling technique among samples to evaluate whether the lack of a standardized technique can result in inconsistent estimates of abundance and species frequencies. In one set of analyses, we varied either the height of the net above the ground, the speed of sampling, or the arc of the sweep. Results indicate that estimates of abundance and community composition derived from sweep samples can vary with relatively minor differences in technique. When we evaluated the effect of having two samplers deliberately mimic each other's technique on close parallel transects, no differences were found among samplers, suggesting that standardization of technique can improve precision.