Accelerated and synchronized oviposition induced by flight of young females may intensify larval outbreaks of the rice leaf roller

Authors: ZHANG, LEI - Chinese Academy Of Agricultural Sciences; PAN, PAN - Chinese Academy Of Agricultural Sciences; Sappington, Thomas; LU, WEIXIANG - Chinese Academy Of Agricultural Sciences; LUO, LIZHI - Chinese Academy Of Agricultural Sciences; JIANG, XINGFU - Chinese Academy Of Agricultural Sciences

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/4/2015
Publication Date: 3/27/2015
Citation: Zhang, L., Pan, P., Sappington, T.W., Lu, W., Luo, L., Jiang, X. 2015. Accelerated and synchronized oviposition induced by flight of young females may intensify larval outbreaks of the rice leaf roller. PLoS One. 10(3): e0121821.

Interpretive Summary: The rice leaf roller is a serious pest of rice in Asia, East Africa, and Australia. It is a long-distance migratory species, and outbreaks may occur in areas that receive a large influx of immigrants. For migratory insect species there is a presumed trade-off in energy reserves, in that energy used for long-distance flight is not available for egg production. To manage this trade-off so that egg production is not harmed too severely, many insects delay reproductive development until after migration has occurred, a combination of characteristics called the "oogenesis flight syndrome". However, in some species, this trade-off may be overestimated, because factors like flight behavior and environmental conditions may reduce its effects. In this study, we used flight mills to examine the reproductive consequences induced by different flight scenarios. We found that the influences of flight on reproduction are not absolutely positive or negative, but instead depend on the age at which the moth begins flight, flight duration, and how many consecutive nights they are flown. The results also show that flight synchronizes egg-laying in groups of females that migrate, which may promote high-density larval outbreaks. Other crop pests, including some in North America probably use the same strategy. This information will be used by university and government scientists in the U.S., China, and throughout the world to better understand the mechanisms controlling explosive growth of outbreak insect populations, and thus lead to better methods for their prediction and management.

Technical Abstract: Physiological management of migration-reproduction trade-offs in energy allocation often includes a package of adaptions referred to as the oogenesis-flight syndrome. In some species, this trade-off may be overestimated, because factors like flight behavior and environmental conditions may mitigate it. In this study, we examined the reproductive consequences induced by different flight scenarios in a widely distributed, economically-important migrant insect, Cnaphalocrocis medinalis. We found that the influences of flight on reproduction are not absolutely positive or negative, but instead depend on the age at which the moth begins flight, flight duration, and how many consecutive nights they are flown. Adult flight on the 1st or 2nd night after emergence, flight for 6h or 12h nightly, and flight on the first two consecutive nights after emergence significantly accelerated onset of oviposition and enhanced synchrony of egg-laying. The latter can contribute to subsequent larval outbreaks. However, flight after the 3rd night, flight for 18h at any age, or flight on 3-4 consecutive nights after adult emergence did not promote reproductive development, and in some scenarios even constrained adult reproduction. These results indicate that there is a migration/reproduction trade-off in C.medinalis, but that it is mitigated or eliminated by flight at the appropriate developmental stage. The strategy of advanced and synchronized oviposition triggered by migratory flight of young females may be common in other migratory insect pests.