Abstract

The diamondback moth, Plutella xylostella L. (Lepidoptera: Plutellidae), is a major pest of Brassica crops worldwide. This study explores the application of Brassica spp. allelochemicals in trapping diamondback moth adults. The effectiveness of eight commercially obtained Brassica spp. volatiles has been investigated, including - (Z)-3-hexenyl acetate, cis-3-hexene-1-ol, β-pinene, sabinene, n-heptanal, allyl isothiocyanate, and Brassica non-volatiles - sinigrin and 4-methylsulfinylbutyl glucosinolate. These allelochemicals were tested at varying concentrations (10 to 90 μg/μL) in laboratory and open-screen cage environment trapping experiments. Cis-3-hexene-1-ol, (Z)-3-hexenyl acetate, sabinene, and β-pinene significantly attracted and trapped more female moths than controls; attraction decreased at higher concentrations. A 1:1 blend of cis-3-hexene-1-ol and (Z)-3-hexenyl acetate displayed optimal attraction in lab and open environment trials for the tested blends. Among the colors tested, green-colored containers proved to be the most effective for trapping. While the plant allelochemicals attracted diamondback moths, signs of non-target cabbage loopers were observed on treated plants. Y-tube olfactometer assays revealed that (Z)-3-hexenyl acetate and cis-3-hexene-1-ol were attractive to both male and female moths. These findings demonstrate the potential of Brassica spp. allelochemicals, particularly cis-3-hexene-1-ol and (Z)-3-hexenyl acetate, for trapping diamondback moths.

Key words: Lepidoptera, Integrated pest management, Plant-insect interactions, Host plant cues, Insect behaviour.