Suitable heat treatment to control Sitophilus zeamais in stored maize and sustain farming

Abstract

Heat treatment is an environment-friendly alternative to chemical insecticides for management of the maize weevil, Sitophilus zeamais, in stored maize. But heat may damage seeds and consequently prevent seed germination or fruiting of plants. In this study, standard procedures were followed utilising the SAMMAZ-52 maize cultivar to determine the suitable heat treatment for effective control of weevils in stored maize without limiting subsequent use in maize farming. Adult male and female weevils were added to 30g of maize grains with moisture content of 14.3% and exposed to temperatures of 50ºC, 60ºC, 70ºC or 80ºC for 30 minutes or 1 hour. 50ºC for 30 minutes or 1 hour was ineffective for killing the weevils. However, 60ºC, 70ºC and 80ºC for 30 minutes or 1 hour completely killed adult weevils present. Viability test showed that maize seeds exposed to 50ºC, 60ºC or 70ºC for 1 hour were viable and germinated after planting, whereas those exposed to 80ºC for 1 hour failed to germinate. All germinated maize plants performed well and yielded cobs with numerous seeds. Temperatures between 60ºC and 70ºC are therefore suitable for controlling S. zeamais in maize stored for both consumption and farming, while 80ºC is suitable for controlling S. zeamais in maize stored only for consumption.