Bioeconomic synergy between tactics for insect eradication in the presence of Allee effects

Abstract

Preventing the establishment of invading pest species can be beneficial with respect to averting future environmental and economic impacts and also in preventing the accumulation of control costs. Allee effects play an important role in the dynamics of newly established, low-density populations by driving small populations into self-extinction, making Allee effects critical in influencing outcomes of eradication efforts. We consider interactions between management tactics in the presence of Allee effects to determine cost-effective and time-efficient combinations to achieve eradication by developing a model that considers pesticide application, predator augmentation and mating disruption as control tactics, using the gypsy moth as a case study. Our findings indicate that given a range of constant expenditure levels, applying moderate levels of pesticides in conjunction with mating disruption increases the Allee threshold which simultaneously substantially decreases the time to eradication relative to either tactic alone. In contrast, increasing predation in conjunction with other tactics requires larger economic expenditures to achieve similar outcomes for the use of pesticide application or mating disruption alone. These results demonstrate the beneficial synergy that may arise from nonlinearities associated with the simultaneous application of multiple eradication tactics and offer new prospects for preventing the establishment of damaging non-native species.

Host-Parasitoid Dynamics and the Success of Biological Control When Parasitoids Are Prone to Allee Effects

“…Biologically, represents the mate-searching efficiency of the species [11], [24]. Various adaptations including volatile sex-pheromones and other signals generally emitted by females, as well as male cognitive and locomotory abilities, tend to increase mate-seaching efficiency; in contrast, stringent mate-choice may actually increase the time taken to find a suitable mate, and thus act as a reduction of [24]. Some of the parasitoid adaptations for attracting mates (pheromone marking, reproductive aggregation) may be less efficient at low densities [24], [58], making density dependent.…”

“…Several theoretical studies have investigated how mating difficulties may translate into demographic effects [19], [20]. Although firm evidence of causal relations between mate-finding Allee effects and establishment success in insect populations is still relatively rare [11], mating failure at low density is often considered to be an important cause of demographic Allee effects in invading species [21], [22], [23], [24], [25].…”

Population spread in patchy landscapes under a strong Allee effect

“…Since some of these species have enormous negative economic and ecological consequences, one would like to understand their dispersal mechanisms to devise appropriate containment strategies. Many invading species face an Allee effect due to factors such as mate finding (Taylor and Hastings, 2005), and these Allee effects can offer control options in addition to pesticide use (Blackwood et al, 2012). Spreading species also encounter habitats of different quality, from highly suitable to completely unsuitable.…”

Economics of invasive species policy and management

“…For example Wu (2000) determines optimal herbicide applications over time, given seed bank dynamics of a weed. Blackwood et al (2012) use a bioeconomic model to examine the synergistic effects of applying multiple control tactics to eradicate the gypsy moth, accounting for the species' population dynamics and the costs of different control measures. They find that combining pesticide application and mating disruption techniques simultaneously can be more cost-effective than either technique alone.…”