METAPOPULATION DYNAMICS AND PEST-CONTROL IN AGRICULTURAL SYSTEMS

In the first metapopulation model, R. Levins investigated the relative benefits of synchronous versus asynchronous application of control me asures for agricultural insect pests. He concluded that synchronous co ntrol measures were optimal because synchrony removes temporary refuge s for the pests. However, his conclusions rest on the assumption that there are no predators whose population dynamics are coupled to those of the pest. Using a novel metapopulation model, we investigate the co nsequences of synchronous versus asynchronous crop planting for the de nsity of a pest either with or without specific predators. We show tha t whereas synchronous planting generally leads to the lowest pest dens ities in the absence of predators, in the presence of predators asynch ronous planting may produce the lowest pest densities. The relative ad vantages of synchronous versus asynchronous planting depend on the pop ulation dynamics and migration rates of pests and predators within fie lds. Our metapopulation model is designed for application to real data , making it possible to select the optimal pest control strategy for p articular crop systems. For many crops, such as rice grown In the Trop ics, current guidelines promote synchronous planting. Our results show that asynchronous planting may potentially be better.