Fungal Diseases Affecting Onion (Allium cepa L.) Grown Under Irrigation Scheme in 2012 and 2013

Onion (Allium cepa) is a vegetable crop grown almost all over the world. It is the second most important vegetables in Nigeria, and fifth in the world market. It is grown mainly for its bulb which is used in every home almost daily. The main use lies in flavouring and seasoning of a wide variety of dishes. In Nigeria, onion cultivation is confined to the semi-arid Northern Guinea Savannah zones. The bulk of onion production occurs under irrigation scheme in the Northern states, good drainage is also very important as onions are badly affected by waterlogged conditions. The survey was carried out during the 2013 irrigation season at the Department of Crop Protection, University of Maiduguri, which lies in the semi-arid zone. Ten samples of diseased onion were sourced at random from different farms within the study area, and sent to the laboratory for macroscopic and microscopic observations and identification of fungal pathogens. The experiment was laid out in a Completely Randomized Design (CRD) and replicated three times. All numerical data obtained were analyzed using Analysis of variance (ANOVA) on Statistix 8.0. Computer software and means separated using Duncan Multiple Range Test. Findings reveals that fungal diseases identified on the onion farms belongs to two Aspergillus species, two from Fusarium and one each from Penicillium, Scopulariopsis, Curvularia, Rhizopus and Alternaria respectively. Of all the various fungi, Aspergillus niger was common in all the samples recording about 88.0 % in unsterilized and 38.0 % in sterilized samples. It also indicates that A. niger had the highest frequency of occurrence (99.0 %) amongst all sampled onion, followed by A. flavus (25.0 %) and R. stolonifer (22.0 %). Also F. graminarium and S. fusca had 11.0 % and 10.0 %, respectively as the least frequency of occurrence. The findings encouraged farmers to take keen interest in field sanitation and seed dressing before planting.