Cost-effectiveness of habitat manipulation as a method of rodent control in Australian macadamia orchards

Abstract

Previous studies ( White et al., 1998) have shown that the manipulation of habitats adjacent to Australian macadamia orchards can result in a reduction in damage due to rodents of up to 65% and that damage was most severe in the first three rows of orchards adjacent to temporally stable large habitats (TSL 1–3) ( White et al., 1997). Cost-effectiveness is the ultimate test of any control strategy, as control practices represent a cost to the industry that must be balanced by a benefit to production. The cost-effectiveness of habitat manipulation as a control strategy was determined in 54 macadamia orchard blocks in Queensland and New South Wales that were representative of the range of adjacent habitat types and damage levels found within major growing areas. The financial break-even point of habitat manipulation (whereby costs and benefits were equal) was dependent on the level of damage in TSL 1–3 and ranged between 5 and 15% with a mean of 9%. These levels are well within the range of damage levels that exist within the industry. Where damage in the first three rows of orchards adjacent to TSL habitats ranged between 15 and 25%, habitat manipulation was shown to be cost-effective in all orchard blocks. The cost-effectiveness of habitat manipulation was reduced to 59% of blocks at damage levels of 10% and it was never cost-effective at damage levels of 5% in TSL 1–3. A comparison of the savings from habitat manipulation and current strategies (baiting with anti-coagulant rodenticides) showed that baiting was unlikely to be as cost-effective at damage levels in TSL 1–3 of greater than 5%. It is only when a control strategy has been shown (a) to reduce damage levels in a cost-effective manner and (b) comply with social and ecological constraints, that it can be classed as effective and acceptable for adoption by the industry. Habitat manipulation, as a strategy for the control of rodents in Australian macadamia orchards, has met these requirements.