Slippery skin: Internal tissue rot
Pathogen: Burkholderia gladioli pv. alliicola (syn. Pseudomonas gladioli pv. alliicola)
Symptoms
The internal tissue will rot in advanced stage. Finally, the internal scales dry and the bulb shrivels. Squeezing the base of infected plants causes the rotted inner portion of the bulbs to slide out through the neck, hence the name slippery skin.
Disease Development
This bacterium requires moisture for infection and grows in the temperature range of 5-41°C (41-106°F). Severe disease can occur during periods of high rainfall combined with strong winds. Heavy irrigation also conducive to this disease. This bacterium is soil-borne and can be readily water-splashed to the foliage and necks where it can enter through wounds. As the plant matures it increases in susceptibility with the mature plant being highly susceptible. In warm weather, approximately 30°C (86°F), infected bulbs can decay within 10 days. However, in storage decay moves slowly, often requiring 1-3 months for a bulb to decay completely.
Disease Management
Harvest onions when bulbs have reached full maturity. Do not store bulbs until they have been properly dried. Minimizing stem and bulb injury and avoiding overhead irrigation when the crop is approaching maturity can reduce losses from this disease. Bulbs should be stored at 0-2°C (32-36°F) with adequate ventilation to prevent condensation from forming on the bulbs.