An early warning system for IPM-based rodent control in smallholder farming systems in Tanzania

We conducted a four-year study in Tanzania to test a method for predicting outbreaks of Mastomys natalensis rats and verify whether such method, based on rainfall variability, could be used in an integrated Pest Management strategy for rodent control. Temporal fluctuations in rodent numbers and breeding activity were monitored at four localities with different rainfall regimes. Breeding peaked towards the end of the main rainy season and continued into the dry period. When the short rains of October-January were unusually abundant and well distributed, reproduction started earlier and rodent numbers increased faster. Where abundant short rains were a normal condition returning every year, such effect was not clear. A method to assess rodent damage to germinating seedlings was found to be robust and can be used for monitoring rodent problems. Using this assessment technique, we showed that the effects of a single control action undertaken at planting time do not persist long enough to protect seedlings, probably due to quick reinvasion of the treated fields by rodents from the surroundings. These observations are formulated into a rodent control package whose steps are to predict rodent outbreaks, to warn farmers and the government of the outbreaks, and to organise control measures in advance.