Methoprene influences reproduction and flight capacity in adults of the rice leaf roller, Cnaphalocrocis medinalis (Guenee) (Lepidoptera: Pyralidae)

Authors: SUN, BEI-BEI - Chinese Academy Of Agricultural Sciences; JIANG, XING-FU - Chinese Academy Of Agricultural Sciences; ZHANG, LEI - Chinese Academy Of Agricultural Sciences; Stanley, David; LUO, LI-ZHI - Chinese Academy Of Agricultural Sciences; LONG, WEI - Chinese Academy Of Agricultural Sciences

Submitted to: Archives of Insect Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/16/2012
Publication Date: 10/9/2012
Citation: Sun, B., Jiang, X., Zhang, L., Stanley, D.W., Luo, L., Long, W. 2012. Methoprene influences reproduction and flight capacity in adults of the rice leaf roller, Cnaphalocrocis medinalis (Guenee) (Lepidoptera: Pyralidae). Archives of Insect Biochemistry and Physiology. 82(1):1-13.

Interpretive Summary: Many of the most serious insect pests of agriculture are migratory insect species, typically moving hundreds of miles in hormone-driven seasonal migrations. Their long-distance travels creates a special problem of predicting the time and place of sudden pest problems. These are typically approached using classical insecticides. Long-term agricultural sustainability is severely threatened by use of classical insecticides. Threats include increasing resistance to insecticides and sharply decreasing environmental quality. Biological control is based on the idea that direct application of certain insect-specific predators, pathogens and parasites can reduce pest insect populations to a point that the pests exert only negligible economic damage. A major problem, however, is migratory insect pests limit the usefulness of biocontrol strategies. In this paper, we examined the hormone basis of migration in a pest insect. We learned that migratory flights can be curtailed in insects treated with a chemical that models the hormone. Scientists who study migratory pest insects will use this information in future research designed understand how pest migration can be manipulated. Ultimately, this research will benefit growers who produce food crops and the people who consume the crops.

Technical Abstract: Juvenile hormone (JH) influences many aspects of insect biology, including oogenesis-flight syndrome tradeoffs between migration and reproduction. Drawing on studies of many migratory insects, we posed the hypothesis that JH influences migratory capacity and oogenesis in the rice leaf roller, Cnaphalocrocis medinalis. We treated adults moths (days 1, 2 and 3 post-emergence) with the JH analog (JHA), methoprene, and then recorded the influences of JHA treatments on reproduction. JHA treatment on day 1 post-emergence, but not on the other days, shortened the preoviposition period, although JHA did not influence total fecundity, oviposition period or longevity. We infer day 1 post-emergence is the JH-sensitive stage to influence reproduction. Therefore we treated moths on day 1 post-emergence with JHA and recorded flight capacity, flight muscle mass and triacylglycerol (TAG) accumulation. JHA treatments did not influence flight speed, but led to reductions in flight durations and flight distances. At day 3 post-treatment (pt), JHA-treated females flew shorter times and less distance than the controls; JHA-treated males, however, only flew shorter times than the controls. JHA treatments led to reductions in flight muscle mass in females at days 2–3 pt and reductions in TAG content in females at day 3 pt, but, these parameters were not influenced by JHA in males. These findings strongly support our hypothesis, from which we infer that JH is a major driver in C. medinalis oogenesis-flight syndrome tradeoffs. Our data also reveal a JH sensitive stage in adulthood during which JH influences the oocyte-flight syndrome in C. medinalis.