Many different types of fungus attack cantaloupe crops. Resulting diseases affect stems, leaves, roots or the plant's fruit. Nematode infestation in soil exacerbates the problem. Spores from fungus can remain dormant in soil for up to 10 years, causing problems for future crops. In addition, some fungus spores are easily spread to other areas by wind or rain. However, specific measures can be taken to control fungus infestations.
Common Cantaloupe Fungal Infections
Southern blight, caused by the fungus Sclerotium rolfsii, produces a water fruit rot that might also attack the stem. Fusarium wilt, a soil-borne fungus, causes the plants to wilt and die. Powdery mildew causes leaf disease. Although most fungi thrive in periods of high humidity, powdery mildew disease favors dry weather. Downy mildew, gummy stem blight and alternaria leafspot all affect the plant's leaves, although gummy stem blight also eventually affects stems and fruits of the plant as well. Anthracnose develops during wet weather, causing leaf spotting and fruit rot.
Spread of Fungus
Fungi easily spread from one plant to another, and from one region to another, via wind, water and soil, making it difficult to completely rid a region of a particular fungal infection. For example, the downy mildew fungus does not survive winters in North Carolina. Yet, the fungus continues to infect North Carolina cantaloupe crops because the sexually reproducing elements from the fungus, the spores, are blown in from southern states.
Fungi spores are designed to last in a dormant state for long periods of time, sometimes 10 years or longer. They lie dormant in the ground or move along with wind or rain. When conditions are favorable for infecting a host, such as planting a new crop, the dormant spores become viable and attack the plant root.
Spores can also be spread by water splash. For example, cercospora leaf spot, a disease caused by the Cercospora fungus, and gummy stem blight both produces spore that disperse through the air and through water splashed about from a rainstorm or sprinkler system.
Effects of Nematodes
Nematode infestation of soil can increase the fungus disease problem. For example, the soil-borne fungus fusarium wilt becomes even more problematic in nematode-rich soil. Proper control of nematodes can help alleviate the severity fungus problems.
Signs of Fungal Infections
Discoloration of the leaves, roots, and stems are signs of fungal infection. For example, in southern blight or fruit rot, symptoms include a white moldy growth on the underside of the fruits. Powdery mildew starts off as a white powdery growth on the underside of older leaves. Downy mildew is characterized by leaf spots having angular yellowish to orange color and diffuse borders that eventually turn brown. Gummy stem blight oozes out a gummy substance on the stem. Alternaria leafspot causes dark brown leaf spots having concentric rings.
Controlling Fungus Infections
Fungal infections in cantaloupe plants can be controlled by selecting fungal-resistance seeds or seeds that have been treated with a fungicide. Other measures include keeping nematode infestation under control; rotating crops in fields so that cucurbits (melons and gourds) are planted in fields that have not had any cucurbit plants in at least two years; selecting well-drained and fertile soil; properly water plants; and being vigilant in checking for the first signs of fungal infection so that treatment can begin immediately.
