Combining Tactics to Exploit Allee Effects for Eradication of Alien Insect Populations

Abstract

Invasive species increasingly threaten ecosystems, food production, and human welfare worldwide. Hundreds of eradication programs have targeted a wide range of nonnative insect species to mitigate the economic and ecological impacts of biological invasions. Many such programs used multiple tactics to achieve this goal, but interactions between tactics have received little formal consideration, specifically as they interact with Allee dynamics. If a population can be driven below an Allee threshold, extinction becomes more probable because of factors such as the failure to find mates, satiate natural enemies, or successfully exploit food resources, as well as demographic and environmental stochasticity. A key implication of an Allee threshold is that the population can be eradicated without the need and expense of killing the last individuals. Some combinations of control tactics could interact with Allee dynamics to increase the probability of successful eradication. Combinations of tactics can be considered to have synergistic (greater efficiency in achieving extinction from the combination), additive (no improvement over single tactics alone), or antagonistic (reduced efficiency from the combination) effects on Allee dynamics. We highlight examples of combinations of tactics likely to act synergistically, additively, or antagonistically on pest populations. By exploiting the interacting effects of multiple tactics on Allee dynamics, the success and cost-effectiveness of eradication programs can be enhanced.

A Comparison of Girdled Ash Detection Trees and Baited Artificial Traps forAgrilus planipennis(Coleoptera: Buprestidae) Detection

“…Early detection allows implementation of management actions during the initial stages of establishment that can slow growth and spread of the pest population, potentially decreasing damage and possibly providing an opportunity for eradication (Shigesada and Kawasaki 1997, Myers et al 2000, Liebhold and Tobin 2008, Suckling et al 2012, Tobin et al 2013. Tools capable of detecting low pest densities are also necessary for accurately delimiting the extent of an infestation and measuring effects of management activities.…”

The Effect of Male and Female Age on <I>Lymantria dispar</I> (Lepidoptera: Lymantriidae) Fecundity

“…The effects of male and female age on reproductive success could also be important in populations managed by mating disruption tactics, which is a strategy used against a number of insect pests (Cardé and Minks 1995, El-Sayed et al 2006, Yamanaka and Liebhold 2009, Witzgall et al 2010, Suckling et al 2012. The concept of mating disruption is based on the introduction of synthetic pheromone into the environment at levels that interfere with mate-Þnding ability through competitive attraction, false trail following, camoußage of the plume produced by calling females, desensitization, habituation, and sensory imbalance (Ridgway et al 1990, Miller et al 2006, Yamanaka 2007.…”

The palm weevilRhynchophorus vulneratusis eradicated from Laguna Beach

“…Below this threshold, populations trend toward extinction (Liebhold and Tobin 2008;Suckling et al 2012). Factors negatively influencing the Allee threshold and increasing extinction risk may include (1) unsuitable climate, (2) suboptimal foods, (3) low genetic variability and (4) control tactics such as the use of pesticides.…”