Transect-based trapping for area-wide delimitation of insects

Authors: CATON, B. - Animal And Plant Health Inspection Service (APHIS); FANG, H - North Carolina State University; PALLIPPARAMBIL, G - North Carolina State University; Manoukis, Nicholas

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/5/2023
Publication Date: 4/30/2023
Citation: Caton, B.P., Fang, H., Pallipparambil, G.R., Manoukis, N. 2023. Transect-based trapping for area-wide delimitation of insects. Journal of Economic Entomology. 116(3):1002-1016. https://doi.org/10.1093/jee/toad059.
DOI: https://doi.org/10.1093/jee/toad059

Interpretive Summary: When a new invasive insect pest is detected, one of the first steps commonly undertaken is known as "delimitation"; for many species this means setting up a trap network to determine the extent of spread of the new pest. The usual approach is to create a regular array of traps over a large area and set this array to a particular density. Here we use a simulation model to test alternative methods of laying out traps for delimitation, particularly using lines (transects- we terms these "trap-sects") across the landscape as opposed to regular grids. Trap-sect designs reduced service distances by 65 to 89 percent at a single site, and most designs had detection probabilities like that of the regular grid.

Technical Abstract: Delimitation trapping survey designs for area-wide (non-localized) insect populations have not been studied extensively, and the default approach is usually a regular trapping grid. We hypothesized that transect-based network designs could give similar detection rates with significantly shorter servicing distances. We used the TrapGrid model to investigate novel “trap-sect” designs with crossed, spoked, and parallel lines, comparing them to a regular grid, in single and multiple-site scenarios. For every design we calculated the minimum servicing distance and determined the simulated mean probability of detection, and we judged overall performance using both metrics. We also subjected the single survey designs to point pattern analysis. Trap-sect designs reduced service distances by 65 to 89 percent at a single site, and most designs had detection probabilities like that of the regular grid. In the area-wide scenario results depended on insect dispersal ability: all designs performed similarly for highly mobile insects, suggesting that designs with the shortest service distances would be best. For less mobile pests, the best trap-sect designs had 4 to 6 parallel lines, or 8 spokes, which reduced servicing distances by 33 to 50 percent. A modified full grid with half as many rows also performed well, but the ability to dynamically place surveys in the field is another advantage of the trap-sect designs. Employing trap-sect designs in area-wide delimitation surveys could significantly reduce costs and increase program flexibility without harming the ability to detect populations.