Problems of Rodenticide-Based Control

There is a growing demand, particularly in developing countries, for rodent control strategies that either have less reliance on chemical rodenticides or promote better use patterns resulting in lower costs for control, minimal risk of contamination of produce and reduced non-target risks. This demand is driven by three main factors. One is the high cost associated with the persistent use of rodenticides prior to or during the growing of each rice crop. The second is the environmental concerns associated with using chemical rodenticides given their ability to cause both primary and secondary poisoning of a wide range of species of mammals and birds. The third is the domestic and international marketing requirements for clean agricultural produce that is produced in an environmentally-friendly and sustainable manner.

Buckle and Smith (1994), and Buckle (1999) provide thorough reviews of the diversity and use of rodenticides for managing rodent populations.

Acute poisons (ZnPh; 1080; etc)

• efficacy depends on the species and poison that is used

• all cause risk of primary poisoning to non-target species; the secondary poison risks (when other animals consume poisoned rats) depends on how quickly the poisons are broken down.

• lack of antidote

• learned bait aversion

Chronic poisons (anti-coagulants)

• efficacy depends on the species and poison that is used; usually higher than acute poisons

• first (multiple feeds required) and second generation (one feed only required) poisons have been developed

• risk to non-target species through secondary poisoning is higher in the second generation poisons

• vitamin K as an antidote

• no learned bait aversion because it takes a rodent 3-7 days to die after eating the poison

• baiting strategies (continuous baiting programs versus pulse baiting; frequency of checking and applying baits; decision rules when to apply and when to cease application)

Use of bait stations

• minimise primary poisoning of non-target species

• protect for rain

• overcome fear of feeding on new food in their environment by free-feeding before using the poison

• where to place them in the habitat is important and depends on cropping system and behaviour and habitat use of rodent species.