Effectiveness of various rodent control measures in cereal crops and plantations in India

In India, crops vulnerable to rodent attack include rice and wheat cereals and coconut, cacao and oil palm plantations. Bandicota bengalensis, Rattus rattus, Tatera indica, Meriones hurrianae, Millardia meltada and Mus sp. are the principal rodents associated with crop damage. In rice 0.005% bromadiolone in bait stations at 15 m interval provided 88.3% control success. Based on live burrow count and baits placed directly in the burrows, the percent control was estimated at 98.8%. Increased yield was recorded in fields treated with bromadiolone as against those of warfarin, zinc phosphide and no treatment. Optimum time of control is six weeks after transplantation. In wheat, which is followed by rice in many areas, bromadiolone bait reduced more than 98% of the rodent population. In coconut plantations, with an average damage of 45.3 nuts/palm/year, amongst a single method of trapping only, warfarin baiting, zinc phosphide baiting and bromadiolone cakes, the latter provided 100% success at the rate of 2 cakes or 33 g/palm in treated plots as indicated by fallen nuts. Single climbing to the crown in case of bromadiolone is an extra advantage in the form of saving in labour in comparison to warfarin and zinc phosphide, also providing 100% success. Cacao intercropped with coconut were treated with bromadiolone wax cakes tied at the fonds at a rate of 2 cakes per tree. After 15 days of treatment, damage was completely reduced. The working index of Economic Threshold Level (ETL), schedule of control operations, monitoring techniques and other integrated measures are discussed.