(Z)-3-Hexenol Induces Tea Defense against Ectropis grisescens in the Field

The tea geometrid Ectropis grisescens is an important pest of tea plant (Camellia sinensis (L.) O. Kuntze). It feeds on the new leaves and tender stems of tea plants, causing serious damage. The green leaf volatile (Z)-3-hexenol (z3HOL) can effectively activate the defense of tea against E. grisescens in the laboratory. In this study, z3HOL was confirmed to activate the tea mitogen-activated protein kinase and jasmonic acid (JA) burst in the laboratory. We investigated effects of z3HOL on the defense responses of tea plants under field conditions. Our results showed that tea plants exposed to z3HOL showed higher levels of JA and polyphenol oxidase (PPO) and emitted increased quantities of volatile organic compounds (VOCs) compared to non-exposed plants. Less E. grisescens larvae were observed in z3HOL-treated plots and less damage was found in z3HOL-treated plants than control. The number of Apanteles sp. and the parasitism of E. grisescens were also enhanced by z3HOL. These findings indicate that synthetic z3HOL can triggers tea defense responses against E. grisescens in the field, and that it could be used as a chemical elicitor to enhance biological control of tea geometrid in the future.