Adult dietary experience influences mortality of the pest melon fly, Zeugodacus cucurbitae (Diptera: Tephritidae), to an ingested toxin

Authors: Mason, Charles; GRUMMER, APRIL - University Of Hawaii; BOSCH, MICHAEL - ARS Postdoctoral Research Associate; SHIKANO, IKKEI - University Of Hawaii

Submitted to: Physiological Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/30/2024
Publication Date: 10/8/2024
Citation: Mason, C.J., Grummer, A., Bosch, M., Shikano, I. 2024. Adult dietary experience influences mortality of the pest melon fly, Zeugodacus cucurbitae (Diptera: Tephritidae), to an ingested toxin. Physiological Entomology. 50(1):77-87. https://doi.org/10.1111/phen.12468.
DOI: https://doi.org/10.1111/phen.12468

Interpretive Summary: Orally consumed toxins are important tools for the management of insect pests. There are several components that might influence insect consumption of toxic baits, one of which being prior nutritional exposure and its impacts on fly foraging and consumption. In our study, we investigated how protein deprivation influenced the effects of ingested boric acid on the pest tephritid melon fly, Zeugodacus cucurbitae. We performed a series of experiments to address the impact of prior diet on mortality, diet consumption, enzymes involved in detoxification and antioxidation, and fly activity. Prior to experiments, insects were either provided a full diet or were protein deprived. Overall, protein deprivation had strong effects on fly interactions with boric acid. In two separate experiments (continuous exposure and short-duration feeding), insects only fed sucrose had significantly higher mortality compared to those consuming protein. Insects that were fed only sucrose consumed more liquid diet over the same duration of the experiments, suggesting compensatory feeding behaviors. Sucrose fed adults had higher activity of enzymes involved in antioxidation, but there was no effect of boric acid in our experiments on the gut enzyme systems. Overall, our results demonstrate that prior diet in fly adulthood can impact subsequent exposure and efficacy of ingested toxicants.

Technical Abstract: Ingested toxins formulated as baits can be effective in the management of insect pests, but their efficacy may be influenced by insect foraging alongside active ingredients. There are several components that might influence insect consumption of toxic baits, one of which being prior nutritional exposure. In our study, we investigated how protein deprivation following adult emergence influences lethal and sub-lethal effects of boric acid on the pest tephritid melon fly, Zeugodacus cucurbitae. We performed a series of experiments to address the impact of prior diet on mortality, diet consumption, enzymes involved in detoxification and antioxidation, and fly activity. Newly emerged melon fly adults were provided either diet containing 3:1 sucrose:yeast hyrdrolysate or just sucrose for three days prior to bioassays. Overall, protein deprivation had a strong effect on fly interactions with boric acid. In two separate experiments (continuous exposure and short-duration feeding), insects only fed sucrose had significantly higher mortality compared to those consuming protein. Insects that were fed only sucrose consumed more liquid diet over the same duration of the experiments, suggesting compensatory feeding behaviors. Sucrose fed adults had higher catalase (1.5×) and superoxide dismutase (1.7×) activities compared to sucrose-yeast fed adults, but we found no effect of boric acid on their activity or that of glutathione-s-transferase or acetylcholinesterase activity. Boric acid consumption also significantly reduced the activity of melon flies. Overall, our results demonstrate that prior diet in fly adulthood can impact subsequent exposure to and efficacy of ingested toxicants.