Investigating plant chemicals and trade-offs between adult preference and larval performance of the rice water weevil

Herbivores use plant chemicals for host plant selection to maximize their own and/or offspring performance. Since host plants that are optimal for mother and offspring are often different and spatially/temporally separated, it remains unclear how plant chemicals are associated with trade-offs between adult preference and larval performance. We found that adults of the rice water weevil (Lissorhoptrus oryzophilus), one of the most important pests on rice in the world, preferred volatiles from barnyard grass over rice and tended to feed and oviposit on barnyard grass compared with rice. In contrast, larvae performed better on rice roots than on barnyard grass roots. Chemical analyses further showed that rice roots had higher nitrogen and soluble protein but lower lignin and cellulose contents than barnyard grass. Together, these results suggest that volatile emissions, specific non-volatile nutritive and defensive chemicals may have close correlations with trade-offs of the adult preference and larval performance between these two hosts. As developing chemical-based technology is one of the main approaches for the control of pest insects, our findings may also contribute to the future efforts for management of the rice water weevil.