Assessment of Rodents’ Postharvest Losses in On-Farm Maize Storage in Kenya

Rodents are one of the major postharvest pests that affect food security by impacting on both food availability and safety. However, knowledge of the impact of rodents in on-farm maize storage systems in Kenya is limited. A survey was conducted in 2014 with a total of 630 farmers spread across the six maize growing agro-ecological zones (AEZs) to assess postharvest losses magnitudes in on-farm maize storage systems in Kenya, and the contribution of rodents to the losses. Experiments were also set in the AEZ identified from the survey study as the main rodents’ hot-spot area with 20 farmers from which 10 stored shelled maize grain or dehusked cobs for 3 months to quantify the actual weight losses due to rodents. Ten (10) other farmers allocated their room and granaries for rodent trapping over 4 months to identify rodents species associated with the losses and their population estimate. Additionally, comparison between rodents damaged grains and non-damaged grains were done for total mould count, mould incidence and for total aflatoxin to evaluate the effect of rodents’ infestations on the grains contamination by storage moulds. Results showed that insects, rodents and moulds were the main storage problems reported by farmers. Storage losses were highest in the moist transitional and moist mid-altitude zones, and lowest in the dry-transitional zone. Overall, rodents represented the second most important cause of storage losses after insects, and were ranked as the main storage problem in the lowland tropical zone, while insects were the main storage problem in the other AEZs. Where maize was stored on cobs, total storage weight losses (farmer estimation) were 11.1  0.7% with rodents causing up to 43% of these losses. Contrastingly, where maize was stored as shelled loose grain, total losses were 15.5 ± 0.6% with rodents accounting for up to 30%. Regression analysis showed that rodents contributed significantly to total storage losses (p < 0.0001), and identified rodent trapping as the main storage practice that significantly (p = 0.001) lowered the losses. Together with insecticides, rodent traps were found to significantly decrease total losses. In the set-up experiments, cumulative weight losses over 3 months of storage ranged from 2.2 to 6.9% and from 5.2 to 18.3% in shelled maize grain and dehusked cobs storage, respectively. Rattus rattus was the only rodents’ species captured during the whole period of trapping in rooms and granaries with a trap success rate varying between 0.62 and 10%. Microbiological analysis showed that total mould count and Fusarium spp. incidence were significantly higher in rodent damaged grain samples than in the non-damaged grain samples whereas no significant differences were obtained for Aspergillus spp. incidence and total aflatoxin level between the two samples. The findings of this study demonstrated that rodents are significant cause of post-harvest losses in on-farm maize storage in Kenya and also impact on smallholder farmers food safety through their infestation. The results however, suggest that improved awareness and right application of insecticides and trap practices could mitigate losses in on farm-stored maize. Moreover more attention must be paid to hygiene around houses and granaries, construction of rat guards around grain store poles, community rodents trapping programmes and food safety and health issues due to rodents’ infestation. Keywords: Postharvest losses, Rodents, Maize, On-farm storage, Food security, Kenya