Manipulating oviposition of the onion fly, Delia antiqua (Meigen): A stimulo-deterrent diversionary approach

Onions and onion models were used to bioassay onion fly host acceptance behavior, with the goal of developing strategies for controlling onion fly (Delia antiqua (Meigen)) oviposition. Stimulo-deterrent diversion (SDD) was developed, where the valued crop is treated with chemical deterrents, and simultaneously, a highly stimulatory ovipositional resource (onions culls) is deployed to concentrate eggs away from the crop.; A wide range of non-onion chemicals deterred onion fly oviposition. In laboratory choice experiments, pungent spices deterred oviposition by 88 to 100%, but were ineffective in no-choice conditions. Compounds with appreciable deterrency are: C8 to C13, intermediate in polarity, and possess either oxygen-containing or nitrile functional groups. When formulated in polyethylene pellets, ({dollar}E{dollar})-cinnamaldehyde had a BR{dollar}sb{lcub}rm 90{rcub}{dollar} (concentration eliciting 90% deterrency) of 1.0% and ({dollar}E{dollar})-methoxycinnamaldehyde had a BR{dollar}sb{lcub}rm 90{rcub}{dollar} of 0.38%. The air concentration of ({dollar}E{dollar})-cinnamaldehyde at its BR{dollar}sb{lcub}rm 90{rcub}{dollar} was 1.7 ng/ml. Deterrents alone may not be sufficient for control; increased oviposition due to deprivation would require high deterrent concentrations.; The interaction of visual (red) and chemical (cinnamaldehyde) deterrent stimuli fit a purely multiplicative model, consistent with separate processing of host stimuli from different modalities during distinct host examining behaviors. Video recordings of examining behavior revealed that red foliage decreased overall activity on a resource, while cinnamaldehyde diminished transitions to ovipositor probing. A greenhouse test of SDD also revealed a multiplicative response when deterrents plus culls protected seedling onions. Total eggs laid on seedlings were: seedlings-only (3185), seedlings + culls (1531), seedlings + deterrent (127), and seedlings + deterrent + culls (69). The probability of an onion fly accepting seedlings was reduced independently by the presence of deterrent and culls.; SDD can reduce pest density in a valued crop. It is suggested that increased pest densities in a diversionary crop will enhance biological control. A population genetics model using two-allele loci for avoidance and physiological resistance traits suggested that SDD combined with conventional insecticide could prevent or reverse pesticide resistance development. Requirements are: (1) higher suitability of the diversionary crop, (2) high finding of the diversionary crop, and (3) deterrents to which a pest is preadapted to respond.