Bounds on Absolute Gypsy Moth ( Lymantria dispar dispar) (Lepidoptera: Erebidae) Population Density as Derived from Counts in Single Milk Carton Traps

Abstract

Simple Summary

Gypsy moth is one of the most devastating forest pests in the Eastern USA. In this paper, we derive a simple formula to interpret catches in monitoring moth traps deployed by management programs.

Abstract

Estimates of absolute pest population density are critical to pest management programs but have been difficult to obtain from capture numbers in pheromone-baited monitoring traps. In this paper, we establish a novel predictive relationship for a probability ( spT _fer(r) ) of catching a male located at a distance r from the trap with a plume reach D. $sp{T}_{fer}\left(r\right)=\left\{\begin{array}{r}\frac{sp{T}_{fer}\left(0\right)}{1+{\left(\frac{r}{D}\right)}^2},r\le R_{max}\\ 0,r>R_{max}\end{array}\right.$ , where spTfer(0) is the probability of catching an insect located next to the trap and Rmax is the maximum dispersal distance for the insect during the trapping period. The maximum dispersal distance for gypsy moth is known to be 1600 m. The probability of catching a gypsy moth male located next to a United States Department of Agriculture (USDA) milk carton pheromone-baited trap is 0.37, the overall probability of catching a male from the entire trapping area ( T _fer ) of ~800 ha is 0.0008, and plume reach of this trap is D = 26 ± 3 m. The equation for spT _fer(r) is used to derive statistical upper and lower bounds (95% confidence interval) on the population density for the given value of a single trap catch. This combination of trap parameters appears to produce an effective trap: even a catch of 1 male provides meaningful lower and upper bounds on absolute population density. Applications in the management programs are discussed, and a look-up table is provided to translate the catches in USDA milk carton pheromone-baited traps to absolute population bounds, which can help design better management strategies.