Fusarium oxysporium f.sp. cepae)
Credits: Biovision-Infonet
(c) David B. Langston, University of Georgia, Bugwood.org
The above ground symptoms constitute yellowing of leaf blades at the tip. The yellowing at later stages covers the whole blade. The affected leaves shrivel and decay. Diseased plants can be easily pulled out because the root system is rotted. Affected roots are dark brown, flattened, hollow and transparent. When diseased bulbs are cut vertically, a brown discolouration is evident. The fungus survives in any soil moisture that permits crop growth. Infection is facilitated by injuries to root system, Losses can occur in the field and in storage.
The disease is most prevalent where onions are grown under high temperature conditions. Although of no economic importance the disease could attack garlic, shallots, chives and leeks. It also can survive in weed, Oxalis corniculata.
What to do:
- Rotate with non-related crops.
- Avoid root injury.
- Carefully harvest the bulbs.
- Proper cure the bulbs before storage.
- Store the bulbs at 0degC / 65-75% relative humidity is recommended.