Detection and monitoring of pink bollworm moths and invasive insects using pheromone traps and encounter rate models.
The pink bollworm moth Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae) is one of the most destructive pests in agriculture. An ongoing eradication program using a combination of sex pheromone monitoring and mating disruption, irradiated sterile moth releases, genetically modified Bt cotton and local insecticide applications have all but exterminated the pink bollworm from the south-western USA and portions of northern Mexico. However, the continued threat of reinvasion from Mexico reinforces the need to improve pheromone-based monitoring. Invasions from other parts of the world such as India, where resistance to single-gene transgenic Bt cotton has evolved, further heightens the need for better monitoring strategies. The mean flight height and standard deviation (SD) of the vertical flight distribution of pink bollworm males were estimated from catches on transparent sticky cylinder traps baited with synthetic pheromone at several heights above-ground. An effective attraction radius (EAR) of a standard pheromone lure was estimated from male moth catches on the pheromone-baited sticky traps and many similar blank traps. The circular EARc was estimated from the spherical EAR and SD. The EAR of a pheromone lure for pink bollworm was 1.03 m, and the EARc was 2.61 m. The mean flight height of males was 0.82 m, and the vertical flight distribution SD was 0.26 m. A computer program simulated male moth movement and capture on various numbers of traps of EARc distributed over areas of 1-100 km2. The simulated catch results were comparable to predictions using the EARc with modified encounter rate equations of Royama and Rogers. The encounter rate equations were solved for initial populations of male moths in the regions, and Poisson statistics were used to calculate population confidence limits. Synthesis and applications. Encounter rate models and Poisson methods can be used to determine levels of pheromone trap densities that are likely to detect and estimate low population levels of resident or invasive pink bollworms and many other pest insect species.