It is never too early for watermelon producers in the Southeast to start thinking about management options for gummy stem blight disease. As Clemson Extension vegetable pathologist Tony Keinath puts it, “Early is on time.”
He reminded growers in The South Carolina Grower that they should allow time to purchase the right fungicides in case of potential shortages.
Keinath’s 2022 gummy stem blight fungicide trial was managed effectively with the rotation of Miravis Prime with Inspire Super and mancozeb. It equated to two applications of each fungicide with six total. Two applications of Miravis Prime improved efficacy compared to Inspire Super rotated 1:1 with mancozeb.
What Didn’t Work?
Monsoon and Mettle rotated with mancozeb performed worse than mancozeb weekly because of DMI (DeMethylation Inhibitors) resistance. Keinath cautions growers not to use Mettle, Rhyme and generic tebuconazole products like Monsoon, Savannah and Tebuzol to control gummy stem blight.
Take Home Message
Miravis Prime is an effective option to add to your fungicide mix to control gummy stem blight. But only use two applications per crop to prevent resistance buildup.
Include mancozeb or chlorothalonil in a watermelon or cantaloupe spray program.
The 2023 Watermelon Spray Guide allows one early-season application of tebuconazole so growers can use up existing fungicides. This exception will disappear in future years.
Gummy stem blight causes lesions on leaves and stems and leads to defoliation. The disease favors warm and wet conditions.