Causal Agent:
Unknown
Distribution:
Worldwide
Symptoms:
Translucent scale typically appears after harvest and worsens after
three to four months of bulb storage. The onion scales take on a
grayish, watery texture, making them appear translucent. All scales
can be affected, however, typically only the second and third fleshy
scales are. These symptoms are similar to freezing injury and can
be distinguished from it only when it is known if the bulbs were
subjected to cold temperatures. Also, frost damage occurs from the
outer scales inward, and opaque white tissues are often produced
within the frost damaged scales.
Conditions
for Disease Development:
Frequent high humidity and temperatures (90°F) during the last
two months of growth and a two to four week delay between during
and cold storage can increase the incidence of this disorder. Storing
onions at high humidity and at 41° to 50°F for a few weeks
prior to cooling to 32°F for storage results in a higher incidence
of this disorder.
Control:
Onion bulbs should be cured properly and stored at the appropriate
temperature (32°F) and relative humidity.
