The bioeconomics of controlling an African rodent pest species
The control problem is specified as timing and duration strategies where the dosage of the poison is kept fixed per month whenever poison is used (consistent with recent practice in Tanzania). The most economically profitable control period seems to be just before the planting season. The damage at planting accounts for such a large portion of the total losses due to rodents, that minimising the population during that short period is enough to reduce yield losses. Controlling for a longer period will reduce rodent populations at a time when they do not damage the crop anyhow, and due to the very high reproductive capacity of the rodents, the population will increase fast as soon as control operations are stopped, repressing any long term effects. Two months of control just before planting season, January and February, or eventually in November and February, seem to be the best overall strategy. These economically most rewarding strategies differ significantly from today’s practice of symptomatic treatment when heavy rodent damage is noticed.
The paper demonstrates that shifting from such practices to more mechanistic control strategies; that is, emphasising the calendar instead of the pest abundance, can substantially improve the economic conditions for the maize producing farmers in the present case of multimammate rats. The best practices compared to today’s symptomatic treatment will typically double the net economic benefit. [author]
