Individual study: Attract and reward: combining chemical ecology and habitat manipulation to enhance biological control in field crops
Simpson M., Gurr G.M., Simmons A.T., Wratten S.D., James D.G, Leeson G., Nicol H.I. & Orre-Gordon G.U.S. (2011) Attract and reward: combining chemical ecology and habitat manipulation to enhance biological control in field crops. Journal of Applied Ecology, 48, 580-590
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Use chemicals to attract natural enemies
A randomised, replicated, controlled study in 2008-2009 in New South Wales, Australia (Simpson et al. 2011) found effects of attractant chemicals varied between crops and natural enemy groups. More predators occurred in broccoli Brassica oleracea treated with a mix of plant chemicals (2.5 predators/trap/day) than for water-treated controls (1.8 predators) one day after spraying. Attractants did not affect total predator numbers in sweetcorn Zea mays or grapevine Vitis vinifera and total parasitoid numbers were unaffected in all three crops. Two parasitoid wasp families (Ceraphronidae and Seclionidae) were attracted to one of four chemicals tested in broccoli and two families (Encyrtidae and Eulophidae) were attracted to one and all attractants respectively, tested in sweetcorn. However, some effects were short-lived or depended on the additional presence of attractive plants. Other natural enemy groups (including up to 11 parasitoid families and 10 predator groups) were not affected by chemical attractants. Butterflies and moths (Lepidoptera) and leafhoppers (Cicadellidae) were not attracted to plots with chemicals. Damage by moth larvae Helicoverpa sp. was lower in sweetcorn treated with methyl anthranilate attractant (1.5% sweetcorn damaged) than in controls (2.7%), but other chemicals had no effect. The study tested five plant chemicals (methyl anthranilate, methyl jasmonate, methyl salicylate, cis-3-hexenyl acetate and benzaldehyde) and two mixes of chemicals.