Light intensity regulates the sexual behaviors of oriental fruit fly Bactrocera dorsalis under laboratory conditions

Abstract

The oriental fruit fly, Bactrocera dorsalis (Hendel), is a devastating pest of citrus fruits. After successful mating, adult females insert their eggs into the ripened fruit, resulting in moldy and rotten fruit and causing great economic losses for the citrus industry. In the field, flies initiate copulatory behaviors as twilight approaches, and decreasing light intensity in this period is the normal stimulus for copulation. In this study, ten light intensities ranging from 0–30 000 lux were set to identify the typical intensity that strongly regulates the copulation behavior of B. dorsalis. Three light intensities found to regulate the copulation behavior were then selected to verify their effects on adult male wing fanning and female chemotaxis towards 2,3,5-trimethylpyrazine (TMP). At last, strong light and complete darkness were artificially combined in the lab to verify whether they could prevent copulation to inform behavioral manipulation of oriental flies in the future. The results indicated that adult flies generally initiated copulatory behaviors at low light intensity (<1 000 lux). Stronger light significantly prevented copulation in proportion to intensity, with nearly no copulation events initiated when light intensity was above 20 000 lux. Both male wing fanning and female chemotaxis towards TMP were attenuated as light intensity became stronger. However, at 10 000 lux, males still fanned their wings to a certain extent while TMP completely lost its attractiveness to females. In the darkness, adults did not initiate any sexual behaviors, e.g., copulation, wing fanning, or chemotaxis to TMP. One hour of strong light (10 000 lux) combined with continuous darkness completely prevented mating. These results show that light condition is an essential factor for copulatory behaviors in the oriental fruit fly. Researchers could thus manipulate light conditions artificially or disrupt the molecular target in flies' light transduction pathway to develop environmentally-friendly techniques to control this pest.