Anthracnose of Cucurbits
Vegetable Disease Information Note 11
Charles W. Averre, Extension Plant Pathologist
[Distribution and Host Range] [Causal
Agent] [Symptoms] [Managment]
Distribution and Host Range
of cucurbits is widely distributed over the world wherever cucurbits are
grown. The disease is common in North Carolina. Anthracnose causes serious
losses when susceptible cultivars of cucumber and watermelon are grown.
Most cultivars of honey dew melon are very susceptible and this disease
is a factor in limiting culture of this crop in the eastern United States.
Cantaloupe, squash, and pumpkin are less susceptible to anthracnose but
occasionally the disease causes losses on the fruit.
is caused by the fungus Glomerella lagenarium (Colletotrichum
orbiculare). The disease is easily diagnosed with a hand lens
or microscope when whisker-like setae
(hairs) can be seen in the pink spore masses.
symptoms of anthracnose vary somewhat on
different hosts. On cucumber leaves the spots start as water soaked areas
and expand into brown spots which are roughly circular, reaching about 1/4
to 1/2 inch in diameter. Small, growing leaves may be distorted and severe
spotting may cause entire leaves to blight.
and stem lesions are shallow, elongate and tan. Lesions on fruit are roughly
circular, sunken and contain pinkish spore masses in moist weather. Spots
on watermelon foliage are black, and a foliar blight may develop giving
a scorched appearance to the planting. The lesions on stem and fruit are
similar to cucumber.
may live two years in the absence of a suitable host. The fungus can be
seed-borne and this is often the source of primary
inoculum. The spores depend upon water for spread and infection; warm
and humid rainy weather at frequent intervals is necessary for disease
development. Spread by wash water on harvested fruit is important when
cucumbers or melons are cleaned before packing. Spores may also be spread
by cultivating equipment or workers when the foliage is wet. The spotted
or striped cucumber beetle can carry the spores from plant to plant
within a field or to adjoining fields.
Cucumbers and Watermelons
seed is desirable. Obtain seed, if possible, that has been produced
in the dry inner valleys of California or other arid regions of the
western United States. Practice at least a one year, preferably two
or three, rotation between cucurbit crops. Avoid moving machinery
or workers in the fields when the foliage is wet. If overhead irrigation
is necessary, irrigate in the early morning so the foliage will dry
before nightfall. Resistant cultivars of watermelon, pickling and
slicing cucumbers are available with desirable horticultural characteristics.
The more commonly grown anthracnose resistant cultivars of watermelon
in North Carolina are Charleston Gray, Sweet Princess, and Garrison.
The resistant pickling cucumbers include Calypso, Chipper, Galaxy,
Carolina, and Explorer, and the most popular resistant slicing cucumbers
are Poinsett and Highmark II (mountains).
are not usually profitable for anthracnose control on watermelons
and spring planted cucumbers when other control practices, such as
crop rotation and resistant cultivars, are used. Fungicides that are
available may vary from year to year. Consult the Vegetable Diseases
section of the North
Carolina Agricultural Chemicals Manual for annual changes. Follow
the manufacturer's label in all cases.
of North Carolina growers have found that a second crop of cucumbers
can be profitable and pickle processing plants want an extended fresh
pack season. Diseases such as anthracnose, however, have been much
more severe in late summer planted cucumbers. Growers have found that
cucumber following cucumber is the most efficient use of land. The
interval between crops may be less than a week and does not allow
for the previous crop debris to be sufficiently decayed to destroy
the anthracnose organism. Late summer cucumbers are exposed to more
fungus spores and have increased chances of becoming infected. They
are usually planted in late July or early August when the temperature
is most favorable for the fungus. In those years when rainfall is
above normal, conditions are such that a disease epidemic can develop.
While a number of cucumber cultivars are resistant to anthracnose,
this resistance is not complete. It is usually high enough for a spring
planting to survive the growing season; however, a late summer planting
may be destroyed several weeks prematurely.
(see N.C. Agricultural Chemicals Manual) should be used on late
summer cucumbers in addition to the use of a resistant cultivar. Begin
spraying with first appearance of the disease, then spray every 5
to 10 days. Use the shorter time interval during rainy weather.
infested field must be planted because a two year rotation is not
possible, then the grower should "Flip plow" the field with a modified
moldboard plow. The procedure to follow is given in Vegetable
Disease Information Note #9.
to Vegetable Disease Notes
Disease Information Notes Home Page
Leaflets about Cucurbits
Information Leaflets Home Page
Carolina Insect Notes
Carolina Agricultural Chemicals Manual
Carolina Cooperative Extension Service
with a specific problem, contact your local North
Carolina Cooperative Extension Service personnel.
[Top of Page]
by North Carolina Cooperative Extension Service
Distributed in furtherance of the Acts of Congress of May 8 and June 30,
1914. Employment and program opportunities are offered to all people regardless
of race, color, national origin, sex, age, or disability. North Carolina
State University at Raleigh, North Carolina A&T State University, U.S.
Department of Agriculture, and local governments cooperating.
Last update to information: July 1991
Web page reformatted Dec. 2000 by Plant
Disease & Insect Clinic