The study sought to confirm reports by farmers and agricultural extension personnel of Prostephanus truncatus (Horn) attacking harvested maize in Mashonaland West and Mashonaland Central provinces of Zimbabwe and to map out, using pheromone trap catch data, the distribution of the pest in the country. A survey of 296 respondents confirmed the presence of P. truncatus in five districts of the provinces. Some respondents reported that the first few sightings of the pest were in 2005 or earlier, while the majority mentioned the 2006/2007 storage season. The map showed a more concentrated distribution of P. truncatus in the northern part of the country moving further inland towards the central and eastern parts of Zimbabwe, indicating possible spread of the pest from the neighbouring countries Zambia and Mozambique. The results of the study indicate legitimate concerns over food security with respect to stored maize grain and seed. The occurrence of P. truncatus in the country has serious implications on training of extension agents and packaging of extension messages that need to be disseminated to the farming community to reduce the impact of the pest. This is the first evidence-based and official documented report of P. truncatus occurrence in Zimbabwe.

The tropical warehouse moth Ephestia cautella (Walker) is an important storage pest of maize grain. The control of this major moth pest relies heavily on the use of synthetic insecticides. We assessed the biological efficacy of a commercial neem oil (Calneem oil) against E. cautella in the laboratory, using the common grain protectant Actellic as a positive control. Contact toxicity, repellency, effects on oviposition, development and grain damage were assessed. The assays were conducted by treating 100 g of maize grains with Calneem oil concentrations of 3, 5 and 7 ml/l; and Actellic at 2 ml/l. Calneem oil significantly (P < 0.05) reduced oviposition rate, development of eggs and immature stages, and emergence rate of E. cautella progeny in maize grains. Grains treated with Calneem oil had significantly (P < 0.05) reduced grain damage in storage, and the oil had a repellency of 53–70% compared with the negative control. Calneem oil protected maize grain against damage by E. cautella for 10 weeks, compared with 20 weeks protection by Actellic. There was no resistance development to the oil for three generations of E. cautella. The insects that survived treatment with the LC90 concentration (12.2 ml/l) of the Calneem oil laid fewer eggs, and some of their progeny were deformed. Calneem oil provided a good level of protection to maize grains against infestation by E. cautella, and may therefore be a suitable substitute for Actellic.