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ANR-0871 Gummy Stem Blight of Cucurbits
Plant Disease Notes
Gummy Stem Blight of Cucurbits
ANR-871, Revised Feb 2004.
Edward J. Sikora, Extension Plant Pathologist, Professor, Entomology and Plant Pathology, Auburn
University
Gummy stem blight, caused
by the fungus Mycosphaerella melonis, is a common disease
of cantaloupes, watermelons, and cucumbers.
Symptoms.
The symptoms of gummy stem blight first appear as grayish green
circular spots between the veins in the lobes of leaves. Spots
turn a dark brown to black with age. The leaf spot stage can be
confused with anthracnose; however, gummy stem lesions are darker
with targetlike or zonate patterns and less deterioration of the
leaf tissue. Spread of the disease begins in the center of the
plant and moves outward. Lesions develop first on the vines at
the nodes and elongate into water-soaked streaks that become pale
brown to gray with time. Stem tissue often cracks and a characteristic
gummy ooze is exuded from the wound. Infected vines die eventually,
and entire plants die occasionally. The disease, unlike anthracnose,
does not attack fruit.
Persistence and Transmission. The fungus overwinters
in old cucurbit vines, in seeds, or in weeds in the cucurbit family.
Gummy stem blight can appear anytime during the season, but most
damage occurs late in the season after the fruit is set. Warm,
wet conditions (temperature 75 degrees F or above, frequent rains,
poor drainage) favor rapid development and spread of the disease.
Control. Gummy stem blight can be controlled by the
following strategies:
- Plant only certified disease-free seeds.
- Plant in well-drained soil free from surface runoff water.
- Follow a weekly spray program with a recommended fungicide
beginning at the first true leaf stage. Continue spraying at
recommended intervals throughout the season, timing sprays just
before rainy periods.
- Practice clean plowdown after harvest or discard all plant
debris.
- Plant cucurbits only once every 4 years, and control both
cucurbit weeds and volunteer cucurbit plants during this period.
Recommended Fungicides. Fungicides are listed here by
active ingredient with examples of brand names in parentheses.
(These brands are usually available to commercial growers.) On
fungicide labels, the active ingredient is usually listed below
the brand name.
Chlorothalonil (Bravo, Equus, Echo); Mancozeb (Manzate 75 DF,
Dithane DF, F-45, Manex II); Maneb (Maneb 80, Manex); Thiophanate-methyl
(Topsin M).
Use chemicals only according
to the directions on the label. Follow all directions, precautions,
and restrictions that are listed. Trade names are used only to
give specific information. The Alabama Cooperative Extension System
does not endorse or guarantee any product and does not recommend
one product instead of another that might be similar. For more
information, call your county Extension office. Look in your telephone
directory under your county's name to find the number.
For more information, contact your county Extension office. Visit http://www.aces.edu/counties or look in your telephone directory under your county's name to find contact information.
Published by the Alabama Cooperative Extension System (Alabama A&M
University and Auburn University), an equal opportunity educator and
employer.
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