Insect species dynamics and associated losses in on-farm stored sesame (Sesamum indicum L.) seeds in major sesame growing areas in Ethiopia

Abstract

Insufficient storage practices and frequent infestations of insect pests pose significant obstacles to sesame production and storage, adversely affecting the quality and quantity of seeds. This forces farmers and traders to sell their crops at lower prices immediately after threshing to avoid market rejection caused by pests and mold damage during storage. The objective of this study was to investigate the insect species dynamics and the losses of on-farm-stored sesame seeds during the 2017- 2018 production year. Sesame seed samples obtained from randomly selected 431farm households in five districts were analyzed to determine the insect species present, insect density, seed weight loss, seed damage, germination percentage, and dockage using R software version 4.2.2. Biophysical parameters such as inter-granular temperature, seed moisture, and relative humidity were also recorded. Furthermore, interviews were conducted with the 431 farm households to gather information on their seed storage methods, practices for controlling insect pests, and the varieties of sesame they produce and store. The findings revealed the presence of 13 arthropod species from four orders (Coleoptera, Hemiptera, Hymenoptera, and Lepidoptera) which belongs to eight families (Tenebrionidae, Silvanidae, Bostrichidae, Curculionidae, Carabidae, Coreidae, Formicidae, and Pyralidae) in the stored sesame seeds at the study site. The most prevalent species was the flour beetle (Tribolium spp.), accounting for 44.26% of the infestation, followed by the rice moth, lesser grain borer, and rice weevil, which constituted 28.2%, 15.72%, and 4.88% of the infestation, respectively. The farmers grew and stored nine different cultivars along with one improved sesame variety called setit-1. On average, there was a 1.97% loss in seed weight, with insect pests causing damage to 8.3% of the seeds. The study districts exhibited an average of 3.79 insects per kilogram of sesame seeds, and the seeds showed a mean germination rate of 77%, which was significantly influenced by the extent of insect damage. The study underscores the significant challenges faced by sesame production and storage in Ethiopia due to inadequate storage practices and infestation by insect pests, resulting in diminished seed quality and quantity. To mitigate the losses incurred from storing sesame on farms, effective measures should be implemented, including improved storage practices and efficient pest control methods.