The effects of non-host plant volatiles on the reproductive behaviour of the Egyptian cotton Leafworm, Spodoptera littoralis (PDF)

Spodoptera littoralis is a major pest of cotton in Egypt, causing serious economic losses.
Egyptian farmers highly appreciate biological control of the pest as synthetic pesticides are
very unsustainable. Phytophagous insects rely on plant volatiles to locate oviposition, feeding
and, mating sites. We tested newly emerged S. littoralis moths by putting them in jars in indirect
contact with leaves of the host plant, Gossypium hirsutum (Gh) and of non-host plants,
Adhatoda vasica (Av) and Picea abies (Pa). Combinations of host and non-host plant leaves
were also observed. Females kept with Gh leaves started calling earlier than the females in all
non-host and the control treatments. Moths exhibited delayed mating when Pa and Gh leaves
were offered in combination. Fecundity was reduced with strong to medium effect when Gh
and Pa and, Gh and Av leaves were offered in combinations, respectively. Pair longevity was
decreased in the absence of Gh leaves or the presence of Av and Pa leaves. Gas
chromatogram electroantennographic detection (GC-EAD) study on the antennae of female S.
littoralis moths revealed three bio-active peaks in headspace collections from Av and five in
Pa, which were subsequently identified through gas chromatography mass spectrometry (GCMS)
by a combination of MS library searches, Kovats indices calculating, and matching the
retention times with synthetic standards if available. The biological activity of synthetic
standards of the identified compounds was further confirmed through electro-antennogram
dose-response tests (EAG). A comprehensive knowledge about these inhibitory effects of Av
and Pa leaves or their combinations, or compounds derived from them, could lead to
sustainable pest management policies.