Sour skin disease of onion

Causal Agent: Burkholderia cepacia (syn. Pseudomonas cepacia)

Symptoms:

• Field symptoms often appear as one or two leaves that have turned a light brown color.
• A watery rot develops at the base of the leaves and proceeds into the neck, allowing the leaves to be easily pulled from the bulb.
• As the disease progresses the outer bulb scales are infected.
• However, the outer most bulb scales and inner bulb scales may not become infected, which distinguishes sour skin from slippery skin where inner bulb scales are infected first.
• Infected scales develop a slimy pale yellow to light brown decay and may separate from adjacent scales allowing the firm center scales to slide out when the bulb is squeezed.
• Infected bulbs often have an acrid, vinegar-like odor due to secondary invaders, especially yeasts, colonizing decaying bulbs.

Control:

• The use of furrow irrigation, instead of overhead and recycled irrigation water, will reduce losses from this disease.
• Do not damage foliage prior to harvest or bulbs during harvest since B. cepacia enters the plant primarily through wounds.
• Onion crops should be harvested at maturity and the bulbs dried quickly.
• Storing onions at cool temperatures 0°C (32°F) with adequate ventilation to prevent condensation on the bulbs.