Assessment of postharvest fungal diseases of maize (Zea mays L) and associated factors in jimma zone, southwestern Ethiopia

Abstract

Maize (Zea mays L) is one of the major crops that are produced in different regions of Ethiopia. Despite the favorable environmental conditions for its production in Jimma Zone, maize is infected by several fungal diseases before and after harvest, due to poor pre- and post-harvest practices/handling. Thus, this study was conducted to assess the distribution of postharvest fungal diseases and associated factors, identify the major causal pathogens of maize in Jimma zone, southwestern Ethiopia during the period 2011 and 2012. This study was conducted at harvest and storage in three maize producing districts of Jimma zone, namely, Sekoru, Omonada and Dedo, respectively, representing low-, mid- and high- altitutde agroecological areas. Three Peasant Associations (PAs) per district and five farmers per PAs were randomly selected, 90 maize samples (45 from the field) and 45 from storage facilities were collected, and brought to Plant Pathology laboratory of Jimma University College of Agriculture and Veterinary Medicine. Fungal isolation and identification from maize kernels were made on Potato Dextrose Agar (PDA) and Czapex Dox Agar. The result showed that mean maize grain damage caused by mould and weevil were 37.8 and 20.9%, respectively, while the mean damage caused by mould, weevil and stalk borer amounted 28.9%, 19.3% and 23.3% respectively. The incidence of mould infected cobs at harvest in the field showed significant difference among PAs in Omonada but non significant for PAs in Sekoru and Dedo districts with respective mean incidence of 14.7%, 19.8% and 20.1% for Sekoru, Omonada and Dedo. Fungal contamination was evaluated from samples collected from field and storage. A total of 1462 fungal isolates were identified from 90 maize cob samples. The most frequent isolated fungi from Sekoru, Omonada and Dedo, respectively, were Fusarium (86.7, 100 and 100%), Penicillium (86.7, 100 and 73.3%),and Drechslera (66.7, 53.3 and 86.7%) species followed by Cladosporium (26.7, 46.7 and 40%) and Aspergillus (33.3, 13.3 and 26.6%) species; from maize samples collected in the field at harvest. Whereas Aspergillus (100, 100 and 93.3%), Fusarium (93.3, 93.3 and 86.6%), Penicillium (80, 73.3 and 100%) species, were most frequent in maize cob sampled from storage in Sekoru, Omonada and Dedo, respectively. This study indicated that, in the field, maize cobs damaged by birds, stalk borers and weevils frequently showed mould growth in kernels, more favored by continuous rainfall upon delayed harvesting resulted in higher crop damage. Further more, improper drying, poor storage structures and storage practices accompanied by rodents attack and weevil infestation aggravated fungal mould contamination in Jimma zone. Thus, it is important to create awareness and sensitize maize producing farmers about high mould contamination and fungal damage, along with possible health hazards of toxigenic fungi in humans and animals upon consumption of such contaminated food grains that needs concentrated efforts to ensure improved pre- and post-harvest handling of maize.