Causal Agent:
Environmental
Distribution:
Worldwide
Symptoms:
Injury from wind, pelting rain or hail is usually visible only on
the side of the leaves that were facing the prevailing winds during
the storm. Spots develop that are typically 1-5mm in diameter, white
to yellow in color and round or irregular in shape. Although rain
damage is rarely serious, hail damage may defoliate a crop. Storm
damage may be confused with Botrytis leaf blight or herbicide injury
and can also make plants more susceptible to fungal and bacterial
pathogens.
Conditions
for Disease Development:
Raindrops, hailstones and soil particles blown by strong winds wound
leaf, neck and flower stalk tissues.
Control:
In areas that are subject to storms, cereal crops can be seeded
in the onions to act as a wind break. Once the onion seedlings are
established selective herbicides can be used to kill the cereal
crop. Broad spectrum fungicides can be sprayed on damaged plants
to reduce the risk of secondary infections.
