Insecticide-induced hormesis in insects

Very low doses of insecticide can have stimulatory effects on insects. This biphasic toxicological phenomenon, whereby a chemical may be toxic at high doses but stimulatory at low doses is called ‘hormesis’. We previously showed that exposure of insects to mild doses of insecticide can greatly stimulate population growth and alter expression of genes involved in stress response and development. However, we still have a relatively poor understanding of the ecological and evolutionary significance of insecticide-induced hormesis for insects. The long-term goal of the research program is to understand the adaptive significance and potential practical applications of hormetic stress responses in insects. This will serve as a centerpiece for the following short-term objectives/questions: - Does insecticide-induced hormesis “prime” insects to better cope with additional stressors they may later experience, and does this persist across generations? - Does insecticide-induced hormesis lead to increased mutation rates and detoxifying enzymes that accelerate development of insecticide resistance? - Can exposure to low doses of pesticide, as seen with other stressors, stimulate reproduction or learning in bees? - Can exposure to low doses of insecticide stimulate reproduction in biocontrol agents (natural enemies) over multiple generations, without affecting overall fitness? Different insect-insecticide models will be used to test hypotheses in laboratory or greenhouse settings, measuring molecular, biochemical, individual, and population endpoints. All experiments will involve training of undergraduate and graduate students, or post-doctoral fellows. The proposed work is original and poised to have high impact internationally. Few studies have tested if mild stress primes organisms for more stress later in life, and we know of no experiments that have studied the problem over multiple generations. We also are not aware of experiments examining the link between hormesis and pesticide resistance, despite there being good reasons to suspect a linkage exists. This is significant given the likely role of hormesis in pest population resurgences and ecological backlash. Though many have studied how to apply hormesis in human health, little effort has explored this with other organisms. The proposed experiments with biocontrol agents are novel and could provide insight on how to improve production of natural enemies in commercial rearing facilities. Our experiments with bees are innovative and have the potential to have high impact for those involved in the pesticide-pollinator debate. Many pesticides are certainly toxic to pollinators, but the possibility of pesticide-induced hormetic responses in bees has been overlooked. If our predictions hold, our results could be a “toxicological awakening” for scientists, legislators, and citizens engaged in pollinator risk assessment.