Attract and reward: combining chemical ecology and habitat manipulation to enhance biological control in field crops

Maria Simpson 1, Geoff Gurr *1, Steve Wratten 2, David James 3, Gary Leeson 4

1 EH Graham Centre for Agricultural Innovation, (Industry & Investment NSW and Charles Sturt Universit
2 Lincoln University, National Centre for Advanced Bio-Protection Technologies, PO Box 84
3 Washington State University, Irrigated Agriculture Research and Extension Centre, 24106 N. Bunn Road
4 Organic Crop Protectants, 42 Halloran St, Lilyfield NSW 2040

Plants produce natural enemy-attracting semiochemicals known as herbivore-induced plant volatiles (HIPVs) in response to herbivore damage.  Synthetic HIPVs deployed in crops have potential to enhance biological control of pests by recruiting natural enemies but these could starve unless well timed to coincide with host/prey availability.  Combining the use of nectar and pollen producing plants with synthetic HIPVs offers scope to improve nutrition for parasitoids and predators.  This project aimed to test the potential for such an ‘attract and reward’ strategy.  Field experiments tested methyl salicylate, methyl anthranilate, methyl jasmonate, benzaldehyde, cis-3-hexenyl acetate, cis-hexen-1-ol at 0.5, 1.0, 2.0%, mixed with Synertrol® (v/v) and buckwheat (Fagopyrum esculentum Moench) as the reward. Synergistic ‘attract and reward’ effects were demonstrated in broccoli with Scelionidae being increased in MeSA treatments with reward.  ‘Attract’ and ‘reward’ alone increased catches of several beneficial hymenoptera and predators in grapevines and sweetcorn as well as broccoli.  In sweet-corn, increases in natural enemy numbers were complemented by effects at the first and second trophic level with plant damage and pest densities reduced.  Laboratory studies indicate that synthetic HIPV application has a short effect on plant head space but longer term effects (ca 6 days) are brought about by triggering endogenous production of HIPVS by treated plants.

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