Under the Scope Feature
Vegetable Storage Rots
A few vegetable samples submitted in December 2012 and January 2013 showed evidence of decay. These vegetables had been in storage when the problems were noted. In the first case, numerous potato tubers exhibited dark lesions on the surface and dark but shallow internal decay when cut. Based on symptoms and isolations from the tissue, this problem was identified as Early Blight, caused by the pathogen Alternaria solani, and it was later confirmed that Early Blight have been noted in the field during the growing season.
In our second example, we received a portion of a head of cabbage exhibiting various gray to black spots on the surface of the leaves. In most cases, these spots were noted to be more severe on one side of the leaf, and concentrated closer to the mid-rib. We found no microscopic evidence of a pathogen on the tissue, and isolations from the tissue also produced no potential pathogen. In this case, damage is suspected of being due to a physiological disorder commonly known as Pepper Spot or Black Speck.
More information on Early Blight may be found in the:
- Compendium of Potato Diseases, 2nd ed. APS Press
- Vegetable MD Online feature: Early Blight More information on Black Speck may be found in the:
- University of Florida Factsheet -"Pepper Spot on Napa Cabbage"
- University of California Factsheet -"Black Speck on Chinese Cabbage"