Major causes of failure of aerial poisoning operations against possums identified were: sublethal toxic loading, undersize sublethal baits, nonlearned behavioral aversion to 1080, and failure to encounter bait. Dislike of bait was not a major cause of failure. Progress has been made towards solving these problems, but failure to encounter bait remains a likely major reason for possums surviving aerial poisoning. Improvements in the aerial sowing of bait are essential if the full benefit of this progress is to be realized
