Herbivore- and elicitor-induced resistance in rice to the rice water weevil (Lissorhoptrus oryzophilus Kuschel) in the laboratory and field.

Feeding by herbivores can change plants in ways that make them more resistant to subsequent herbivory. Such induced responses are better-studied in a number of model dicots than in rice and other cereals. In a series of greenhouse and field experiments, we assessed the effects of prior herbivory by the fall armyworm, Spodoptera frugiperda (J.E. Smith) and of exogenous applications of jasmonic acid (JA) on the resistance of rice plants to the rice water weevil, Lissorhoptrus oryzophilus (Kuschel), the major pest of rice in the United States. Prior feeding by S. frugiperda and treatment of plants with exogenous JA resulted in increases in the resistance of plants to the weevil. Increases in resistance were manifested as reduced numbers of eggs and first-instars associated with armyworm-injured or JA-treated plants relative to control plants. In field experiments, there was a transient but significant reduction in the number of immature L. oryzophilus on JA-treated plants relative to untreated plants. To our knowledge, this is the first example of direct induced resistance in rice demonstrated in small-plot field experiments. We discuss the potential for the use of elicitor induced resistance in rice.