Dragon fruit (Hylocereus undatus), commonly called pitaya, is a member of the cactus family known for its ornate and colorful fruit. This Mexican native thrives in the tropical regions of Asia, North America and South America. The stems of this plant can grow up to 20 feet long, while its flowers can reach almost 1 foot in diameter and length. Several bacterial and fungal pathogens cause stem rot diseases on dragon fruit plants, diminishing their aesthetic value and threatening the survival of the entire plant.
Bacterial Stem Rot
A variation of the Xanthomonas campestris bacteria is associated with stem rot disease on dragon fruit. This type of bacteria has a multitude of variations that attack a large number of plants, including vegetable and tree species. This stem rot is also known as black rot, because infected tissue turns to a dark black or brown color. Controlling insect pests is an integral part of managing the spread of this disease. Aphids and mites are common pests that can transmit viruses and bacteria to healthy plants. According to the International Tropical Fruits Network, the Erwinia caratovora bacteria is known to cause a stem rot disease in Malaysia, which is one of the main producers of dragon fruit.
Fungal Stem Rot
Several fungal agents can damage the stems of dragon fruit plants. The Fusarium oxysporium fungus is a problematic pathogen responsible for diseases on trees, shrubs and herbaceous plants. The Fusarium fungus causes light discoloration of infected tissue and causes stems to lose their consistency, according to the Ontario Ministry of Agriculture, Food and Rural Affairs. Damaged shoots eventually break as the decay destroys the fibrous material in the plant's stems. Other fungi, like those in the Pantoea genus, are also associated with stem disease in dragon fruit.
The long stems of dragon fruit are a liability in the face of stem rot diseases. If the base of the stem is infected, the entire stem and all the leaves, flowers and fruit attached to it may die. Infected plants have an increased risk of suffering from environmental damage, like drought or excessive heat, and are more likely to be attacked by other pathogenic fungi or bacteria. Unsightly yellow and brown discolorations resulting from stem rot diseases mar the aesthetic value of dragon fruit plants, which are prized for their ornamental value.
Inspecting dragon fruit plants on a regular basis and ensuring they are growing in a healthy environment is critical to preventing an outbreak of stem rot disease. Heavy soils that become easily saturated are not suitable for dragon fruit plants. Overly moist environments foster the growth of fungi and may weaken the plant by strangling its root system. If an infection of stem rot is identified on a plant, all infected stems should be removed as soon as possible. Plant debris should be cleared to prevent the fungus from surviving in rotting tissue on the ground.
- North Dakota State University; Leaf Spot and Stem Rot (Bacterial Blight) of Gernaium (Pelargonium spp.); Raymond J. Taylor et al.; July 1996
- University of Hawaii Cooperative Extension; Pitaya; Francis Zee et al.; June 2004
- Interntional Tropical Fruits Network; Pitaya Pest and Diseases Management; Ahmad Kamil et al.
- Ontario Ministry of Agriculture, Food and Rural Affairs; Fusarium Stem and Root Rot of Greenhouse Cucumber; Raymond Cerkauskas; August 2009