Use of permethrin coated nets to protect stored grain from pests infestations

Surveys carried out in some villages of Democratic Republic of the Congo showed that insect pests are a major cause of food loss for rural populations. Cereal grains are often compromised by pests in the field and during storage. Among cereals cultivated for family consumption in these areas of Africa, mainly maize and rice are both seriously infested by Coleopteran pests belonging to the genus Sitophilus. Any approach currently adopted to solve this problem, as the manual removal of visible insects, is often inadequate or insufficient. Due to the limited availability of chemical insecticides and their high price in these countries, our aim is to study a simple and cheap way to protect grain after harvest. The technology derives from anti-malaria mosquito nets, also known as insecticide treated nets (ITNs) or bednets, modified for the new purpose. Nets consist in fine-mesh polyester coated with permethrin (2.0%), a synthetic second generation pyrethroid that gives repellent and insecticide effect, while ensuring a high human safety. The idea is to use these nets to wrap jute bags or other containers in which grain is commonly stored in poor countries. Preliminary bioassays with adults of Sitophilus oryzae showed that knock-down values for 50% and 95% of exposed insects (KD50 and KD95, respectively) were equal to 4.8 and 9.5 minutes. We are currently carrying out further in vivo bioassays (in Italy) and field studies (in Congo) to test the efficacy of the treated net. The coating of structures for grain preservation could be a viable sustainable strategy for limiting food losses in countries that lack resources and technologies for pest control.