The 1993 strychnine baiting program for mouse control in South Australian grain crops. I. Efficacy

Abstract

The grain-growing areas of South Australia were affected by a severe mouse plague during the winter and spring of 1993. Damage to recently sown and maturing crops was minimised by broadcasting 0.3% strychnine-treated wheat across affected crops, at a rate of 1 kg ha^-1. Three indices were used to measure relative mouse abundance before and after treatment: counts of active mouse holes, bait card consumption, and live-trapping. Hole counts and live-trapping both underestimated treatment effects. Bait card consumption provided the most accurate indication of treatment effects. In crops treated across their entire area, treatment reduced bait card consumption by 87%, with 95% reduction in 18 of 28 crops monitored. In most cases, baiting stopped damage by mice and allowed farmers to establish healthy crops where previously mice had removed all the seed sown, and resown, prior to treatment. Perimeter baiting was less successful owing to rapid reinvasion of treated areas, and reduced average bait card consumption by only 16%. Strychnine baiting in crop stubbles was ineffective where weed seeds were abundant.