Efficacy of zinc phosphide, strychnine and chlorpyrifos as rodenticides for the control of house mice in South Australian cereal crops

Abstract

Replicated field trials were conducted to compare the efficacy of zinc phosphide, strychnine and chlorpyrifos for the control of house mice (Mus domesticus) infesting recently sown wheat crops in South Australia. Bait was prepared using whole-wheat grain or grain-based pellets and broadcast into the crops at 1 kg ha^–1. Treatment with zinc phosphide reduced mouse numbers by 98%. Two treatments with strychnine baits, applied 11 days apart, also reduced mouse numbers by 98% with no evidence of bait aversion in mice that survived the initial treatment. On the basis of these and other published results, zinc phosphide is considered an effective alternative to strychnine for control of house mice in cereal crops. Chlorpyrifos baits reduced mouse numbers by less than 10%. The trial began too late in the growing season to prevent substantial mouse damage to seed grain and seedlings. The number of seedlings established at treatment time one month after sowing explained 84% of variation in crop yield. Mouse damage is estimated to have reduced yield by more than 0.5 t ha^–1 or 15% of potential yield and cost the grower more than $30 000 in lost production from the 300-ha study area.