PERFORMANCE OF POST-HARVEST STORAGE BAGS AND DIATOMACEOUS EARTH FOR THE PROTECTION OF STORED MAIZE AGAINST INSECT PEST INFESTATIONS

Abstract

Maize is an important staple crop widely used in domestic and industrial processes. It is usually stored in Polypropylene (PP) bags, where it is prone to heavy insect infestations, resulting in high economic losses. A number of recent interventions to prevent insect infestations during grain storage include Diatomaceous Earth (DE) and novel bags such as ZeroFly (ZF) and Purdue Improved Crop Storage (PICS). However, there is paucity of data on their effectiveness and optimal use in insect pest management. Therefore, this study was conducted to determine the effectiveness of different storage bags and DE against stored-insect pests of maize. The study was conducted between February, 2017 and January, 2018 in a storehouse at Arisekola Market, Bodija, Ibadan. Pristine 50 kg SWAN 2 maize variety was stored using eight different bag treatments comprising: PP (control) and ZF, DE admixed in PP and ZF (PPDE and ZFDE), single and double hermetic liners in PP (PP1L and PICS), single and double hermetic liners in ZF (ZF1L and ZF2L). A stack of three replicates for each treatment was placed on separate pallet and arranged one meter apart. In addition, for each ZF1L, ZF2L, PP1L and PICS, two sets comprising 3 replicates/set were stored for destructive sampling every four-months using standard procedure. Maize in ZF, PP, ZFDE and PPDE were sampled monthly. Insect population count, insect damaged kernel, maize weight loss and insect perforation on bags were determined through standard procedures. Maize quality was determined through standard seed germination method, maize Moisture Content (MC) was measured by MC meter and aflatoxin level by Thin-Layer Chromatography. Data were analysed using descriptive statistics and ANOVA at α0.05. Total insect population of 5,945 in all treatment bags comprised predominantly Sitophilus zeamais (2,593), followed by Tribolium castaneum (1,298), Liposcelis spp. (1,193) and the least occurring Cryptolestes ferrugineus (861). Percentage of insect species per bag: ZF2L (0.2) and ZF1L (0.3) were significantly lower than the population in ZFDE (3.2) and PPDE (7.9), but higher in ZF (51.8) and PP (35.4). Insect damaged kernel was significantly low in ZF2L (0.4±0.0%), ZF1L (0.5±0.0%) and ZFDE (0.8±0.3%) compared to ZF (16.9±1.6%) and PP (5.4±0.9%). The maize weight loss was significantly low in ZF2L (0.1±0.0%), PICS (0.2±0.0%) and ZFDE (0.2±0.1%) compared to ZF (6.7±0.8%). The number of insect perforations on ZF2L (0.0±0.0), PICS (1.3±0.4) and ZF (17.0±3.1) were significantly lower compared with the control, PP (51.5±5.7). Seed germination rate (97.5±0.6%) in ZF2L and PICS were significantly higher than PP (78.3±0.1%) and ZF (66.0±2.3%). The initial MC of the maize in treatment bags was 11.4±0.1%, but the final MC in ZF2L (12.2±0.1%) was significantly lower than in PP (13.5±0.1%). Aflatoxin levels in maize in all treatment bags were within the recommended limits (4 µg/kg) of Standards Organisation of Nigeria, except the PP (5.0 µg/kg). Hermetic storage bags and diatomaceous earth were effective at controlling insect infestations and preserved stored maize quality. Therefore, they could be used in postharvest storage interventions.