This material is provided courtesy of:
Bhabesh Dutta, Associate Professor and Vegetable Disease Specialist, University of Georgia
Ron Gitaitis, Professor Emeritus, Phytobacteriologist, University of Georgia
A variety of diseases can affect onions. Being able to recognize the symptoms of various diseases can go a long way in implementing effective management strategies.
Below are four photos of diseases of onion, along with some key information about each. Can you identify each disease?
1. Management of this disease favored by cool wet conditions relies on sprays applied using forecast models that are based on sporangia development under favorable conditions of temperature and relative humidity.
2. The common name of this disease caused by the fungus Glomerella cingulate shares its name with a 1996 film starring Helen Hunt and Bill Paxton.
3. This disease is caused by a soil-borne pathogen that can survive in soil for many years as chlamydospores or as a saprophyte on crop residues. The disease generally occurs with warm soil temperatures in fields previously used for onion production. The entire plant may collapse and, if the plant is pulled, it often comes out without any roots attached since they have decayed.
4. This disease caused by an obligate parasite can be quite destructive on foliage, reduce yields and produce distinct diamond-shaped lesions on seed scapes.
Answers:
1. Downy mildew
2. Twister
3. Fusarium basal rot
4. Iris yellow spot
