An extensive study on the baseline toxicity of five aphid pests in broadacre agriculture to four major pesticides has been published in Crop & Pasture Science.
This work was led by cesar scientists, Dr Paul Umina and Annabel Clouston, in conjunction with Owain Edwards at CSIRO, and was funded through GRDC.
Populations of cabbage aphid, turnip aphid, blue-green aphid, cowpea aphid and oat aphid, collected from major agricultural regions of Australia, were tested in the laboratory for their sensitivity to pirimicarb, dimethoate, α- cypermethrin and imidacloprid (all of which have different modes of action) using a leaf-dip assay approach.
The good news is that none of these fives species was found to have evolved insecticide resistance.
This work indicated that insecticide sensitivity is dictated more by the species of aphid, rather than species locality or cropping practices.
Oat aphids exhibited the lowest sensitivity to the four insecticides tested, showing less than 100% mortality when α-cypermethrin was tested at field rates for some field populations.
Cabbage aphid, turnip aphid, blue-green aphid and cowpea aphid had sensitivity levels comparable to, or higher, than those reported for the same species overseas where data was available.
Interestingly, the chemical responses of cowpea aphids were varied depending on the region and plant type from which the aphids were collected. This suggests that populations of cowpea aphid may be responding to local selection pressures, and that future movement towards tolerance of field rates is possible.
This work is critical for evaluating future resistance in Australian aphid populations and exploring potential shifts in population resistance.