Courtesy University of FloridaSymptoms of the new Pseudomonas disease (pictured) on a watermelon leaf were slightly different than those of angular leaf spot.A bacterial cousin of the organism responsible for angular leaf spot caused a severe outbreak in commercial watermelon fields throughout Florida in April.
A group of University of Florida researchers identified the culprit as a Pseudominas species that is genetically similar to the P. synringae pv. lachrymans that causes angular leaf spot of watermelon, according to a grower newsletter.
They are Nicholas Dufault, a plant pathologist, and Christopher Ferguson, doctor of plant medicine, both at Gainesville; and Mathews Paret, a plant pathologist at the North Florida Research and Education Center in Quincy.
Disease symptoms also were slightly different than those of angular leaf spot.
Bacterial diseases of cucurbits are common throughout the Southeast, but the researchers said the severity of this epidemic was "extraordinary."
They blamed the long periods of rain accompanied by cool day and night time temperatures for providing ideal conditions for disease development.
Once temperatures climbed into the 70s and 80s during late May, the impact of the pathogen began to decrease.
Will the pathogen be a problem in 2014?
The researchers say it's probably unlikely because of different environmental conditions.
Nevertheless, they recommended scouting on a regular basis should wet and cool conditions be present in April.
Buying certified seed or removing transplants with leaf spot symptoms are two ways to help reduce the amount of inoculum brought into the field.
Rotating to a non-cucurbit crop in fields that had the pathogen and proper weed control are two additional ways to reduce the chances of repeat infections.