Keele Research Repository

BACKGROUND: The manipulation of herbivore-induced volatile organic compounds (HI-VOCs) via the application of the inducers BTH [benzo (1,2,3) thiadiazole-7-carbothioic acid S-methyl ester] and Laminarin [β-1,3-glucan] is known to enhance the attractiveness of caterpillar-damaged cotton and maize plants to parasitoids. To test if this is also the case for legumes, we treated cowpea with these inducers and studied the effects on HI-VOC emissions and the attraction of three generalist endoparasitoids. RESULTS: After applying the inducers and subjecting the plants to either real or mimicked herbivory by Spodoptera littoralis caterpillars, females of the parasitoids Campoletis sonorensis and Microplitis rufiventris showed a strong preference for BTH treated plants, whereas Cotesia marginiventris females were strongly attracted to both BTH and Laminarin treated plants with real or mimicked herbivory. Treated plants emitted more of certain HI-VOCs, but considerably less indole, linalool and several sesquiterpenes. Multivariate data analysis revealed that enhanced wasp attraction after treatment was correlated with high relative concentrations of nonanal, α-pinene, (E)-β-ocimene and DMNT, and with low relative concentrations of indole, (S)-linalool and (E)-β-farnesene. Inducer treatments had no significant effect on leaf consumption by the caterpillars. CONCLUSION: Our findings confirm that treating cowpea plants with inducers can enhance their attractiveness to biological control agents.