- September 15, 2025
- More articles By John Tucker
- Photos by Mengjun Hu
WINE ENTHUSIASTS are increasingly filling their glasses with products from Maryland vineyards, spurring an eightfold growth in the number of wineries since the 2000s and generating billions of dollars in the state.
But unlike the dry, temperate climes of traditional wine regions of California or Italy, the DMV’s warm, wet summers invite fungus to thrive. If just 5% of a grape bunch is rotting, the product can be ruined, pressuring growers to apply fungicide liberally throughout the six-month growing season despite high costs, potential environmental threats and health risks.
Associate Professor Mengjun Hu, a plant pathologist who assists growers through the University of Maryland Extension, discovered a way to cut fungicide use while protecting quality. He spent two years culling diseased grapes from more than 20 regional vineyards. In the lab, his team identified the pathogen responsible for most decay while understanding the control window of blight: the late growing season.
“For this type of rot, the crop isn’t vulnerable in the early season, so application then is unnecessary and ineffective,” says Hu. Growers adopting his recommendation saw significant boosts in fruit quality.
He and his team further developed a mathematical model that predicts disease based on weather data, along with growth stage, which the Maryland Grape Growers Association incorporated into a digital tool for members. The model allows producers to pinpoint the best fungicide-application timing at their location for maximum effect. Those using the model can expect fungicide reduction by at least 30%, says Hu.
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