STRAW AND WINTER FLOODING BENEFIT MOSQUITOES AND OTHER INSECTS IN A RICE AGROECOSYSTEM

Abstract

Rice fields are widespread agroecosystems that provide wetland habitat for many species, including pests like mosquitoes and beneficial insects. They can be used as models to understand how basal resources affect food web dynamics in seasonal wetlands. Rice field management may also influence adjacent communities by affecting mosquitoes, wildlife, and air quality. Rice straw incorporation and winter flooding have become common methods used to prepare seedbeds, largely replacing burning of straw. These methods could affect aquatic insects, including mosquitoes, because they increase nutrient availability during the growing season. We studied 16 fields where straw was either burned or incorporated into soil after the previous growing season; these treatments were crossed with either winter flooding or no winter flooding. Algae, mosquitoes, other herbivorous insects and predatory insects all responded positively to one or both treatments that increased nutrients (straw incorporation and winter flooding). While the overall increase in insect production could benefit wildlife, mosquito abatement personnel may need to monitor unburned fields more closely. The issue of mosquito production adds to the complexity of agricultural and environmental concerns bearing on rice field management. Straw incorporation and winter flooding reduce particulate pollutants caused by burning, reduce fertilizer needs, and increase densities of beneficial insects. However, these techniques may increase mosquitoes, methane production, and fungal diseases of rice. Further improvement of straw management practices could minimize these problems.