Common Pests and Disease Problems of Watermelons

Plant Diseases Common to Watermelon

Fusarium Wilt

Watermelons are attacked by Fusarium wilt at all stages of development. Seeds may decay in the soil. Seedlings wilt collapse and die before or after emergence.

Older plants wilt, wither, and die any time during the growing season. If melons do form, they are generally small and unpalatable.


Anthracnose is a Very destructive disease of watermelons and other curcubits. Anthracnose attacks all above-ground parts of the plant. Watermelon can be infected at any stage of development, however, disease symptoms are first noticed as round to angular reddish brown spots on older leaves.

Spots may later dry, turn almost black and tear out, giving a leaf a ragged appearance. Often the leaves at the center of the plant are killed first, leaving the stem and a portion of the runners bare.


Bonide Infuse Systemic Disease Control ConcentrateDisease treatment Product for Watermelon  Treats powdery mildew, anthracnose, black spot and dollar spot [See Label]

Blossom End Rot

Blossom End Rot can be caused by a calcium deficiency and occurs frequently on acid soils or during stress periods on soils with seemingly sufficient calcium.

Recommended treatment – Blossom-End Rot ControlWatermelon Blossom End Rot Control

Gummy Stem Blight

Causes damping off, crown rot, leaf spot, stem canker, and fruit rot of watermelons. Lesions on the cotyledons and leaves are round or irregular and brown in color. Lesions on the crown and stem are brown and turn white as they age. Early infection usually comes from diseased seeds.

As the season advances, gummy stem blight attacks vines causing elongated, water soaked areas that become light brown to gray. Cankers are most common near the crown of the plant. Gum oozes from the stem cracks, and runners usually die one at a time. Gummy Stem Blight generally does not cause fruit rot in watermelons.

See Also: Gummy Stem Blight and Phoma Blight on Cucurbits

Watermelon Mosaic Virus

Caused by two distinct viruses referred to as Watermelon Mosaic Number I and Watermelon Mosaic Number II [How clever!].

The most common symptom is mottling of the leaf, some plants are stunted with abnormally shaped leaves. The diseases is usually spread by aphids which can spread through an entire planting during the growing season.

Common Pests

  1. Aphids
  2. Worms – wireworms, cutworms, and pickle worms
  3. Beetles -Cucumber Beetles
  4. Mites– red spider mites
  5. Vegetable leafminer– Colorless to bright yellow maggot, up to 3 mm long, with pointed head, makes serpentine mines in leaves; each mine slightly enlarged at one end

Nematodes – microscopic worms which live in the soil and feed on the host plants roots preventing the the plants from taking up the nutrients they need to grow . Some forms of nematodes are highly beneficial , while others can wreak total destruction . Tomato plant nematodes are prevalent throughout North America, but they are most damaging to tomato plants in the Southern regions of the US.

Pest Control Methods

Citric acid destroys the wax coating of the insect’s respiratory system. When applied directly, the insect suffocates. It is biodegradable. Persons with known citrus allergies may be affected. Do not spray on red mature fruits. Effective on most insects including aphids, beetles, caterpillars, cutworms, earwigs, flies, gnats, lacebugs, leafhoppers, loopers, mites, moths, snails/slugs, mosquitoes, whiteflies

Hot Pepper Wax repels bugs from your plants, fruits and flowers. 100% natural spray uses pepper extract and wax to effectively discourage pests. Helps to reduce stress on cuttings.

Related: What Stunts Watermelon Growth?