Fungus on Dendrobium Orchids

Phytophthora Root Rot

• Phytophthora root rot of dendrobium orchids is commonly referred to as black rot because of its effects on the orchid’s foliage and roots. This soil-borne disease restricts the dendrobium orchid’s vascular system, resulting in its inability to transport water and nutrients throughout the plant. Though soil-borne, phytophthora root rot causes this orchid’s foliage to develop water-soaked lesions that develop into large, black and decaying spots. The blooms become wilted and the shoots may fail to open. The dendrobium orchid’s stems and branches turn yellow and experience dieback while the entire orchid experience growth stunt. There is no cure for phytophthora root rot and the infected plant should be removed and destroyed.

Anthracnose

• Anthracnose is a leaf spot disease that targets all areas of the dendrobium orchid. Caused by a collection of varying fungi, the disease causes the dendrobium’s young foliage to develop small, tan-colored spots that develop into large, decaying lesions. The infected foliage becomes curled and distorted while the mature foliage generally remains unaffected. Severe anthracnose infections are often accompanied by girdling cankers on the branches, stems and base of the orchid. The dendrobium orchid’s stems, twigs and blooms are killed by the anthracnose infection when the disease is not treated promptly.

Petal Blight

• Though the fungal species is named after the camellia, petal blight disease infects the dendrobium orchid, as well as other flowers and plants. The infected dendrobium orchid begins to display symptoms within 24 hours of infection. The dendrobium’s blooms develop small, dark-colored spots that expand into large, brown and yellow lesions. Though the blooms do not wilt or decay, the petals are dried from the infection and defoliate from the tree.

Care

• Although there is no cure for phytophthora root rot, most of the dendrobium orchid’s fungal infections are treatable. The infected dendrobium orchid should be treated upon the first signs of infection to prevent permanent injury and growth. Remove all diseased and injured foliage, stems and blooms with sharp, sterile shears. Treat the dendrobium orchid with fungicidal treatments that are designed for orchid fungal infections. Apply the fungicides according to the package’s instructions for best results. Prevent infections by keeping the dendrobium orchid’s planting area free of debris and defoliation. Thin its densely foliated interior to increase the sunlight and air that flows through the plant.