Cantaloupe Diseases and Their Control
Vegetable Disease Information Note 13 (VDIN-0013)
Extension Plant Pathology

Cantaloupes are affected by several diseases which often cause serious crop losses and steps must be taken to control them. Often diseases may not be present, however, commercial growers should always employ preventative measure that will help avoid the diseases or reduce their severity if they appear. Diseases are usually more frequent and serious in late season and during periods of high humidity. Diseases are a major cause for the rapid decline of cantaloupes after the first harvest. A total disease control program, as described in this publication, along with good cultural practices, as described in Horticultural Leaflet Number 8, will increase yields and quality and extend the productive life of the plant.

Major Diseases

Root-knot caused by nematodes (Meloidogyne spp.) that live in the soil and are very destructive to cantaloupes and may also make wilt diseases more severe. The immature nematodes enter young roots to feed and cause galls or swellings on the roots. Where the disease is severe, the plants are stunted, frequently wilt on hot days, and may die prematurely. Root-knot is more prevalent on sandy soils and more severe during hot, dry weather, and losses of 20 to 80% are not uncommon. Crop rotations of 2 to 4 years with non- susceptible corn, oats, and fescue will reduce the nematode problem.

Fruit and stem rot (Southern blight), caused by the soil-borne fungus, Sclerotium rolfsii, causes a watery fruit rot and may also attack the stem. In advanced stages, brown mustard seed-like reproductive bodies (the sclerotia) are found in abundance embedded in the white moldy growth on the underside of the fruits or around the base of the infected stems. The disease is controlled by burying sclerotia and previous crop trash 10 to 14 inches deep using moldboard turning plows equipped with concave disk coulters. Subsequent cultivation should be as shallow as possible. Growing the plants on plastic or polyethylene-covered beds will greatly reduce the fruit rot stage.

Fusarium wilt is caused by the soil-borne fungus Fusarium oxysporum f. melonis and infected plants wilt and die. The fungus remains in the soil for 3 or more years, thus long rotations with non-cucurbit hosts are necessary to reduce soil infestation. The disease is much worse in fields infested with nematodes; an effective nematode control program will reduce the severity. Fusarium wilt-resistant varieties should be planted in areas where the disease is a problem.

Powdery mildew caused by the fungus Erysiphe cichoracearum or Sphaerotheca fuligena is a leaf disease favored by dry weather. It usually starts as white, powdery growths about 1/4 inches in diameter on the underside of older leaves; eventually all green leaf and stem surfaces become infected and leaves wither. Resistant varieties may be available.

Downy mildew, caused by the fungus Pseudoperonospora cubensis is a leaf disease that may be serious during wet periods in mid-to-late season. The fungus does not overwinter in North Carolina, but the spores are blown in from southern states, and occasionally the disease never appears. Leaf spots 1/4 to 1/2 inch in diameter are recognized by their initial angular yellowish to orange color with diffuse borders. Later the spots turn brown and the entire leaf may become blighted.

Gummy stem blight, caused by the fungus Didymella bryoniae, affects the leaves, stems and fruits. On the stem, a gummy substance exudes from lesions, hence the name. It produces large, dark leafspots with diffuse borders. In some cases there is considerable leaf margin blighting without stem lesions. Avoid planting after cotton, snap beans, okra, or any cucurbit crop. Because the disease can be seed-borne, only disease-free, treated seed should be planted.

Anthracnose, caused by the fungus Colletotrichum lagenarium is a leafspot and fruit rot disease. During wet weather the leafspots and fruit lesions develop a salmon-colored substance (spore masses). One or two year rotations with non-cucurbit crops are useful in reducing the disease. Anthracnose is seed-borne and only disease-free, and treated seed should be planted.

Alternaria leafspot, caused by the fungus Alternaria cucumerina, is recognized by the dark brown leaf spots with concentric rings.

Soft rot of fruit is caused by the bacterium Erwinia carotovora and related species. They usually enter at the stem end of the fruit and cause a soft, smelly rot. Soft rots also start where the skin of the fruit has been broken by accident or by chewing insects. These rots are more common in warm, wet weather.

Disease Control Program for Cantaloupes

Diseases of cantaloupes can be controlled by properly using all disease control practices described herein. This program will help avoid diseases and minimize their severity if they do occur. Consult the NC Agricultural Chemicals Manual or your local extension service for recommendations for fungicides and nematode control.

Seed
Select varieties with resistance to prevalent disease if available,
Purchase seed of known quality that have been produced under disease-free conditions and that have been treated with a fungicide.

Soil
Select fields that have not been in any cucurbit crop for at least 2 years,
Select well-drained and fertile fields,
Take soil samples and have them assayed for fertility and nematodes

Other Links

Plant Disease Information Notes Home Page
North Carolina Insect Notes
North Carolina Agricultural Chemicals Manual

Recommendations of specific chemicals are based upon information on the manufacturer's label and performance in a limited number of trials. Because environmental conditions and methods of application by growers may vary widely, performance of the chemical will not always conform to the safety and pest control standards indicated by experimental data. All recommendations for pesticide use were legal at the time of publication, but the status of registration and use patterns are subject to change by actions of state and federal regulatory agencies.

Published 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.

Revised Sept. 2007 Tom Creswell