Onion (Allium cepa L.) is an important vegetable produced across a wide range of latitudes in the world. Allium
crops are the most indispensable vegetable crops used as condiments in most Ethiopian cuisine. Among them, onion
(Allium cepa L.) is one of the oldest known and an important bulbous vegetable crop grown in Ethiopia. It is used in
preparation of different foods and in therapeutic medicine in the country. It has a great potential to produce every
year for both local consumption and export with an average yield of 10.77 tons per hectare [1].
The area under onion is increasing from time to time mainly due to its high profitability per unit area and ease of
production, and the increases in small scale irrigation areas. The crop is produced both under rain fed in the meher
season and under irrigation in the off season. In many areas of the country, the off season crop (under irrigation)
constitutes much of the area under onion production. Despite areas increase, the productivity of onion is much lower than other African countries. The low productivity could be attributed to poor insect pest and disease management
and other problems.