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Sublethal concentration of insecticide amplifies interference competition in a tortrix moth
Barbara Joncour1, William A Nelson1
1Department of Biology, Queen's University, 116 Barrie Street, Kingston K7L 3N6, ON, Canada.
Ecotoxicology and Environmental Safety
|May 20, 2021
Summary
Sublethal concentrations of spinosad insecticide amplify interference competition in moth larvae, increasing mortality through aggressive interactions. This highlights the need to assess insecticide impacts on competition mechanisms for accurate population predictions.
Area of Science:
- Ecology
- Insect toxicology
- Population dynamics
Background:
- Insecticides are widely used, but sublethal effects on organisms and population dynamics are poorly understood.
- Intraspecific competition, particularly interference, can be altered by sublethal insecticide exposure, impacting life histories.
- Few studies have disentangled insecticide effects on interference versus exploitative competition.
Purpose of the Study:
- To investigate the sublethal effects of spinosad on interference competition in Adoxophyes honmai larvae.
- To determine how altered interference competition impacts the life histories of these moths.
- To differentiate spinosad's effects on interference versus exploitative competition.
Main Methods:
- Paired experiments were conducted to isolate the effects of spinosad on interference competition.
- Larval behavior, movement ability, and mortality were assessed under varying spinosad concentrations.
- Intraspecific interactions, including conspecific killing, were quantified.
Main Results:
- Sublethal spinosad exposure significantly amplified interference competition among Adoxophyes honmai larvae.
- Increased interference was strongly linked to higher mortality rates, suggesting enhanced aggressive interactions like cannibalism.
- Spinosad impaired larval movement, potentially increasing vulnerability to conspecific attacks or enhancing defensive aggression.
Conclusions:
- Sublethal insecticide concentrations can alter life histories by changing the strength of interference competition.
- Understanding the impact of insecticides on interference mechanisms is crucial for predicting population dynamics of pest and non-target species.
- This research underscores the importance of considering behavioral and competitive alterations in ecotoxicological risk assessments.
