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Leaf Blight

When leaf blight affects melon crops such as cantaloupe, honeydews, and watermelons, the disease typically doesn't infect the fruit. However, leaf loss due to leaf blight diminishes your harvests by reducing plant vigor and exposing fruit to sunscald. With cucurbit-family crops, leaf blight hits melons hardest, but it also affects close relatives such as cucumbers, zucchini, pumpkins, and winter squash.

Wet, rainy conditions favor leaf blight's development, while wind and water aid its spread. Damage worsens when leaf wetness and warm temperatures coincide. The youngest and oldest cucurbit plants are most vulnerable to this disease.

Leaf Blight Identification/Symptoms: Leaf blight symptoms on cucurbits typically show first on older leaves, closest to the plant's base. The brown-black leaf spots grow in target-like, concentric rings. Unlike water-soaked spots caused by gummy stem blight, leaf blight spots look dry. As the disease progresses, leaves turn brown, curl up, and die.

How to Control Leaf Blight: As with many common diseases of edible plants, prevention and early treatment are key to controlling leaf blight in melons and related crops. Start treatments as soon as plants get their first true set of leaves or when conditions favor the disease.

Daconil® fungicides from GardenTech® brand offer three-way protection to prevent leaf blight and to stop and control active diseases. These highly effective products treat melons, cucumbers, pumpkins, and squash right up to your harvest day:

  • Daconil® Fungicide Ready-to-Use is ideal for small garden areas, container gardens, and individual plants in edible landscapes. Just shake the grab-and-go spray bottle and spray all plant surfaces until thoroughly wet.
  • Daconil® Fungicide Concentrate, used with a hand-held, hose-end, or tank-style sprayer, offers an economical option for larger areas. Measuring is simple with the convenient measuring cap. Add water, mix well, and spray all plant surfaces to the point of runoff.

Leaf Blight Tips: Wet garden tools and clothing help spread leaf blight, so don't work a wet melon patch. Dispose of infected vines and clean up well before winter sets in; leaf blight fungi overwinter in plant debris.

Always read product labels thoroughly and follow instructions, including guidelines for treatable plants, application rates and frequencies, and pre-harvest intervals (PHI) for edible crops.

GardenTech is a registered trademark of Gulfstream Home and Garden, Inc.

Daconil is a registered trademark of GB Biosciences Corp.

Photo Credit:

Clemson University - USDA Cooperative Extension Slide Series, Bugwood.org (CC BY 3.0 US)

Clemson University - USDA Cooperative Extension Slide Series, Bugwood.org (CC BY 3.0 US)

David B. Langston, University of Georgia, Bugwood.org (CC BY 3.0 US)

Don Ferrin, Louisiana State University Agricultural Center, Bugwood.org (CC BY 3.0 US)