# Utilizing Tea Plant Synomones to Attract Encarsia smithi for Suppressing Aleurocanthus spiniferus in Tea Plantations

## TL;DR

This study shows how tea plant odors can attract a parasitic wasp to control a harmful whitefly pest in tea plantations.

## Contribution

The study identifies and applies synomones from tea plants to attract Encarsia smithi wasps for biological control of Aleurocanthus spiniferus.

## Key findings

- Tea leaves damaged by whiteflies emit trans-2-hexenal and methyl salicylate, which attract Encarsia smithi wasps.
- A 3:1 blend of trans-2-hexenal and methyl salicylate lures attracted the highest number of wasps in field tests.
- Using the synomone-based lure increased parasitism rates of whiteflies by 2–3 times in treated plots.

## Abstract

The citrus spiny whitefly, Aleurocanthus spiniferus Quaintance (Hemiptera: Aleyrodidae), is an important pest of tea, Camellia sinensis (L.) Kuntze (Theales: Theaceae). Parasitic wasp, Encarsia smithi Silvestri (Hymenoptera: Aphelinidae), is one of the dominant natural enemies of the whitefly. Generally, the whitefly produces four generations per year in Chinese tea plant growing areas. The wasp adult stages are basically synchronized with the nymphal stages of the whitefly. In an indoor Y-tube olfactometer bioassay, odors from both whitefly-pierced tea leaves and adjacent intact tea leaves significantly attracted the wasps, with elevated amounts of trans-2-hexenal and methyl salicylate (MeSA) detected from these two types of tea leaves. A four-arm olfactometer bioassay verified that these two compounds and their binary blends significantly attracted the wasps. Bud green sticky boards baited with trans-2-hexenal (10−2 g mL−1), MeSA (10−2 g mL−1), and five blends of trans-2-hexenal and MeSA (1:1, 2:1, 3:1, 4:1 and 5:1, respectively, v/v) at 10−2 g mL−1 in hexane solutions captured significantly more wasps than did the un-baited boards, with the 3:1 blend catching the highest number of wasps. To enhance whitefly parasitism by the wasps, from early April to early August, the Attractant 2 lures (each holding a total mass of 80 mg of the 3:1 blend) were hung on tea branches and refreshed every 30 days. Deployment of the controlled release synomone-based attractant lures resulted in 2–3 fold higher parasitism rates by the wasps in the treated plots/sections than those in the CK plots/sections during both the peak periods of whitefly pupae of generation 2 from late July to early August and generation 3 in late August. This study demonstrated that herbivore-induced tea volatiles can be formulated as a synomone-based lure for controlling the whitefly through attracting E. smithi in tea plantations.