What does global warming mean for stored-grain protection? Options for Prostephanus truncatus (Horn) control at increased temperatures

Abstract

Global climate change is expected to accelerate reproduction, development and activity of stored-product insect pests and degradation of grain protectants hence compromising efficacy of available storage pest management technologies. However, there is little information on these effects. The current laboratory study examined the effect of increasing temperatures on the efficacy of stored maize grain protectants and hermetic containers in controlling Prostephanus truncatus (Horn). In Experiment I, three commercial synthetic grain pesticides (cocktails of an organophosphate and a pyrethroid or a neonicotinoid) and two farmer-practices (neem leaf powder and wood ash) were tested on shelled maize grain. In Experiment II, four storage containers, viz Purdue Improved Crop Storage (PICS) bag, Super Grain bag (SGB), metal silo (MS) and polypropylene bag (PP) (all containing untreated maize) were tested. Both experiments were conducted for 12 weeks at 32 °C, 38 °C and mean ambient temperature of 26 °C; with three replicates per treatment. All treatments were artificially infested with laboratory-reared adult P. truncatus. Sampling was at baseline (0 weeks) and 4-weekly intervals. Overall, results showed significant differences in grain damage and weight losses between non-synthetic and synthetic grain protectants in all treatments at all tested conditions. The hermetic storage containers kept mean insect grain damage below 6.4% compared to 24.5% in the untreated control at all the experimental conditions. These results indicate that the use of synthetic grain protectants and hermetic storage containers (SGB, PICS and MS) in the management of P. truncatus may not be negatively affected by projected warmer temperatures of 32 °C or 38 °C; suggesting these storage technologies will remain efficacious under sub-Saharan Africa’s warming climates.