Laboratory and field evaluation of floral odours from African marigold, Tagetes erecta, and sweet pea, Lathyrus odoratus, as kairomones for the cotton bollworm Helicoverpa armigera

Significant increases in upa armigera in a wind-tunnel were obtained with air entrained headspace samples of African marigold, Tagetes erecta, flowers (P=0.014), and sweet pea, Lathyrus odoratus, flowers (P=0.047). Identification of the compounds contained in the Porapak Q extracts was done by GC-MS. Direct EAG was used to screen for the most electrophysiologically active natural extracts and GC-EAG was used in screening for compounds to test in the wind-tunnel. Two 4-component synthetic kairomonal blends were identified which caused significant increases in upwind flight in the wind-tunnel (P<0.001 and P=0.014 for marigold and sweet pea blends respectively). Funnel traps baited with floral odours were tested for their ability to catch Helicoverpa armigera and other insects in the field in Israel. Significantly more H. armigera, another noctuid pest, Autographa gamma, the honeybee Apis spp., a wasp Halictus spp. and lacewings (Chrysopidae) were caught in traps baited with synthetic marigold, Tagetes erecta, and sweet pea, Lathyrus odoratus, floral volatiles than in unbaited control traps. The marigold blend contained benzaldehyde, (±)-linalool, phenylacetaldehyde and (S)(-)-limonene, and the sweet pea blend (-)-linalool, phenylacetaldehyde, benzyl alcohol and diacetone (4-hydroxy-4-methyl-2-pentanone) in the natural ratio. Although the target specificity and level of attraction obtained with the floral traps was too low for mass trapping, the floral traps could possibly be used for monitoring female H. armigera populations. These findings are discussed in relation to the potential use of floral kairomones in integrated control of H. armigera.