Individual study: Effects of an herbivore-induced plant volatile on arthropods from three trophic levels in brassicas
Orre G.U.S., Wratten S.D., Jonsson M. & Hale R.J. (2010) Effects of an herbivore-induced plant volatile on arthropods from three trophic levels in brassicas. Biological Control, 53, 62-67
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Use chemicals to attract natural enemies
A randomised, replicated, controlled study in 2007 in Canterbury, New Zealand (Orre et al. 2010) found higher numbers of the parasitoid wasp Diadegma semiclausum in turnip Brassica rapa plots with a methyl salicylate lure (averaging 1.6-7.2 wasps/trap) than in controls without the chemical (1.4-6.4 wasps). Other natural enemies, including brown lacewings Micromus tasmaniae and hoverflies (Syrphidae), were captured too infrequently to be analysed. More pest leaf miners Scaptomyza flava occurred in plots with the chemical attractant (2-17 leaf miners/trap) than controls (1-12 leaf miners). The parasitic wasp Anacharis zealandica, an enemy of beneficial brown lacewings, was also more abundant in plots with methyl salicylate (0.0-3.3 wasps/trap) than in controls (0.0-1.2 wasps). The authors suggest that attracting beneficial insects with chemicals can also attract potentially harmful insects. One sachet of synthetic methyl salicylate was hung above treated plots and was replenished twice during the study period (24 April to 12 June 2007). No chemical was used in controls. Treated and control plots were replicated 12 times in a 400 x 470 m field. Natural enemies, pests and parasites of natural enemies were monitored using yellow sticky traps.