Warm and wet weather creates ideal conditions for anthracnose, a fungal disease that causes significant damage to cucurbits, primarily cucumbers, muskmelons and watermelons.

Anthracnose survives on diseased crop debris from previous years or infected seed for up to 2 years, and it depends on water for spread and infection. Under wet conditions, the fungus releases airborne spores that infect vines and foliage. This disease can also be spread by equipment or workers when foliage is wet. The spores will not be released without moisture or in temperatures below 40º F or above 86º F, which is why anthracnose is most dangerous in hot, humid conditions.

Infection usually becomes apparent mid-season and affects foliage differently depending on the type of cucurbit crop. Infected petioles and stems on melons have shallow, elongated, and tan lesions. On cucumbers, leaf lesions begin as water-soaked spots which expand to yellow-brownish circular spots. Leaf lesions on watermelons are circular at first, and later grow together in irregular patches of dead tissue.

The most noticeable sign of anthracnose infection is on the fruit where circular, black, sunken cankers appear. When there is moisture present, these lesions become covered in salmon-colored masses of spores.

To best manage anthracnose, growers should implement a preventive program that incorporates a mix of cultural and chemical controls, and should consider the following guidelines:

• Use clean seeds. Seeds are the primary source of inoculum for anthracnose so it is important to start with clean seed.
• Plant disease-resistant varieties. To protect vulnerable seedlings, we recommend planting varieties that are resistant to anthracnose such as Constable cucumber variety or many of our resistant watermelon varieties, including Sweet Dawn, Melody, or Excursion.
• Rotate crops in a three-year rotation. Anthracnose can live for 2 years in the absence of a suitable host. A 3 year crop rotation will allow enough time for the disease to die out.
• Apply an effective fungicide. For foliar protection against this damaging disease, we recommend Quadris Top^® It demonstrates rapid uptake with translaminar movement of difenoconazole and xylem-systemic movement of azoxystrobin for robust, sustainable disease control.

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