Do triple bag hermetic storage Control Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) in stored maize in Mozambique?

Prostephanus truncatus is a serious and dominant pest of stored maize in Mozambique. Before the introduction of P. truncatus in Mozambique in 1999, weight loss in stored maize in small scale farmers’ system was about 10 to 12% and Sitophilus zeamais was the most important pest of stored maize. However, the level of losses increased dramatically after the introduction and establishment of P. truncatus in Mozambique to 61.5% (about 5 times higher) and a reduction in storage period and availability of food from 10 to 12 months before to 6 months. The shortage of food that occurs annually in Mozambique is mainly due to the weaknesses in storage systems leading to high losses of maize during the storage period due to storage insect pest’s infestation and thus contributing to food insecurity in the country. The use of synthetic insecticides has been recommended for the control of P. truncatus and other storage insect pests. However, there is little or no use of chemical insecticides in small scale storage systems because of the high cost and hazardous effects on human health and environment. The present study was conducted to assess the effectiveness of triple bag hermetic storage (PICS bag) in controlling P. truncatus in storage in Mozambique. The study was conducted in a completely randomized block design with 6 treatments including T1= Maize + PICS bag + P. truncatus + Actellic; T2 = Maize + PICS bag + P. truncatus; T3 = Maize + PICS bag; T4 = Maize + normal (PP) bag + P. truncatus + Actellic; T5 = Maize + normal (PP) bag + P. truncatus; T6 = Maize + normal (PP) bag (control), arranged in 4 replications. P. truncatus population density and maize weight loss were estimated monthly from 500 g of maize sample, during 180 days. At the start of the experiment, before infesting bags, the number of insects and the weight loss were zero for all the treatments. At 180 days of storage in all PICS bag treatments, the number of insects was 0.0, 7.0±2.7 and 0.0 in T1, T2 and T3, while the weight loss was 0.0%, 0.3±0.3% and 0.0% respectively. In contrary, at 180 days of storage in the PP bag treatments there was a significant increase in the numbers of insects. The number of insects was 107.3±45.5, 701.8±77.4 and 61.0±36.3 in T4, T5 and T6, with weight loss of 1.4±0.8%, 46.3±18.1% and 4.8±0.0% respectively. These results suggest that the population of P. truncatus can be effectively controlled by using the PICS bags. Thus, the use of PICS bags could be recommended for use in the small scale farmer’s storage system in the country.