Use of the effective attraction radius in three dimensions (EAR) and two dimensions (EARc) for detection, monitoring, and mass trapping

Invasive species are initially at low populations and must be detected with pheromone-baited traps or colored traps. Areas in which a pest insect has been eradicated need to be monitored for new introductions.  Mass trapping uses a higher density of traps to trap a large proportion of the population. The key question is how many traps of a given attractiveness are needed to detect a low-level population or to be useful in mass trapping. The effective attraction radius (EAR) is a spherical radius that represents the catching-power of attractive traps. For example, if a blank trap of known dimensions catches one insect per day by simple interception while an attractive trap catches 10 insects per day, then effectively the attractive trap is 10 times the silhouette area of the blank trap. The EAR/EARc can effectively substitute for the dimensions of a pheromone plume and the complex probabilities of insect orientation upwind to the lure in the trap. The EAR can be converted to a two-dimensional EARc for use in simulation models with a simple formula using the standard deviation of the vertical flight distribution of a particular insect. The EARc depends on the insect, the lure composition and strength, and primarily applies to traps that intercept insects in flight (barrier and sticky traps). Computer simulation of individual insects moving in a correlated random walk was used with the EARc to explore efficacy of trapping when parameters such as the size of the EARc, the density of EARc (representing lures in traps and/or natural pheromone of insects), the density of searching insects, and the mean distance that a searching insect travels in the simulated time period were varied. Encounter rate equations were modified for use with the EARc (two dimensions) and compared to some of the simulation models. While simulations can take hours or longer to generate predictions, the encounter rate equations duplicate the simulation results instantly. The models are useful in understanding which variables need be measured in the field to develop a successful detection, monitoring, or mass trapping program.