Plant pathologists work to fight gummy stem blight in watermelons

07/11/2013 09:08:00 AM
Vicky Boyd

Katherine StevensonCourtesy University of GeorgiaKatherine StevensonAs gummy stem blight goes, so goes the Georgia watermelon season.

The fungal disease can cause lesions on leaves and turn stems into a gooey mush, devastating untreated fields, according to a news release.

That's why Katherine Stevenson, a University of Georgia plant pathologist, and colleagues study fungicides and develop rotational programs.

The goal is to control the disease while at the same time prolong the usefulness of commercially registered fungicides.

To prove the impact of the disease on the state's watermelon industry, she noted the drop in farm-gate value in 2009 to $98 million from the previous year's $139 million.

She attributed the decrease to gummy stem blight.

The disease, caused by the fungus Didymella bryoniae, causes some losses each year.

But warm, rainy weather, like those in 2012, can cause the disease to explode.

The best control would be to breed resistant varieties. Until they are available, growers have to rely on chemicals.

Several fungicides are registered to control gummy stem blight but not totally eliminate it.

Since they have a single-site mode of action, Stevenson said rotating with other modes of action is essential to slow resistance from developing.

The fungus already has become less sensitive to a few of those fungicides.

She works with vegetable horticulturist David Langston to develop effective fungicide programs.

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