Differential Changes in Tea Quality as Influenced by Insect Herbivory

Abstract

Tea quality depends on plant metabolites that impact flavor, aroma, and health-beneficial properties. Plants respond to insect herbivory by altering the concentration and blend of these metabolites, and many secondary metabolites are produced only after insect attack. Research in tea and other plants shows that insect herbivores affect the concentrations of metabolites important to tea quality such as volatiles, polyphenols, methylxanthines, and amino acids. Plants, including tea, respond differently to different insect herbivores by producing different blends of metabolites. Tea plant metabolites also vary in their responses to increasing herbivore density which results in a change in metabolite blends as herbivore density changes. Because climate change is predicted to impact the density and species composition of insect herbivores in tea-growing regions of the world, induction of metabolic changes by insect herbivores represents a potentially important indirect effect of climate change on tea quality. Although it is often assumed that insect attack is detrimental to tea quality, there are some cases where tea quality is improved by herbivore-induced changes in tea metabolites. It is therefore possible that allowing some insect herbivory could be an important strategy for mitigating detrimental effects of climate on tea quality.