Affection: soft bacterial rot and brown bacterial rot

Pathogen: Pectobacterium (syn. Erwinia)

Symptoms: small watery spots on the leaves, often with yellow edges. Untreated, the infection will spread quickly and affect the roots and leaves, spreading more slowly in the case of rhizomes and pseudobulbs. An unpleasant odor may be noticed.

Taxa affected: Phalaenopsis, Vanda, Dendrobium, Paphiopedilum, Grammatophyllum, Oncidium, Cambria.

Recommended treatment: Funguran, Champ, Aliette.

Affection: brown bacterial spotting

The pathogen: Acidovorax (syn. Pseudomonas)

Symptoms: the most common and dangerous condition of the Phalaenopsis genus, it is manifested by the appearance of small, soft spots, in the form of swellings filled with liquid, of small size, located anywhere on the leaves, initially green in color; later, as their size increases, the color changes to brown or black, drying and appearing as deep areas in the leaf surface. When the infection reaches the tip of the leaf, it secretes liquid infected with bacteria, which contributes to the contamination of other plants. Prevalent in the warm season.

Affected taxa: Phalaenopsis, Cattleya, mainly any species.

Treatment: Aliette, Champ, Funguran.

Affection: brown rot, fungal root rot

The pathogen: Rhizoctonia

Symptoms: root rot occurs when the culture medium decomposes, the drainage is insufficient and the plants are overwatered, its installation being favored by mechanical injuries to the roots or due to the deposition of salts, following excessive fertilization. In Cattleya species, the pathogen settles more slowly, from the oldest to the newest pseudobulbs, climbing along the pseudobulbs and producing their browning, followed by their hardening. The roots of old plants, like other plant organs, will die. Although it is a disease of the roots, the symptoms can also be observed in the aerial parts, being similar to those produced by fusarium, namely the yellowing of the leaves, their drying and raisining, followed by their falling and the browning of the pseudobulbs from the lower part towards the top.

Affected taxa: Phalaenopsis, Paphiopedilum, Miltonia, Oncidium and its hybrids, with extension on the artificial genus Cambria.

Treatment: Folpan, Dithane.

Disease: anthracnose

Pathogens: Colletotrichum, Glomerella

Symptoms: it affects the aerial parts of the plant, most often the leaves, whose tip turns brown from the apex, moving towards the base. It develops spots, sometimes with the appearance of concentric circles, sometimes in the form of dark bands, in large numbers, positioned transversely on the laminar surface. The affected areas are clearly defined, sometimes slightly deepened, while the rest of the leaf has a normal appearance. Sporiferous bodies develop in the infected areas. Watery, black or brown pustules appear on the flowers, generally higher and appear preferably on the dorsal parts of the older petals and sepals, which can fuse and cover the entire flower. The pathogen most frequently associated with anthracnose is Colletotrichum gloeosporioides (in the asexual stage, the sexual stage being known as Glomerella cingulata). Another known pathogen is Colletotrichum theobromicola, which was not known in orchids until now. It produces a chlorotic (greenish) spot on the upper surface of the leaf, but the respective spots also correspond on the lower surface, forming deep or necrotic spots at the same time.

Affected taxa: Paphiopedilum, Masevallia, Phalaenopsis, Stanhopea, Oncidium, Cattleya, Dendrobium.

Treatment: Dithane.

Affection: leaf spotting

Pathogens: Cercospora, Pseudocercospora, Guignardia, Phyllostycta, Septoria.

Symptoms:

Cercospora: the infection initially appears as a yellow spot on the lower part of the leaf, and shortly after it appears, it also becomes visible on the upper part. As its surface increases, it presents a slightly deep and necrotic appearance and turns purple-brown to black-violet. The spots continue to increase in size, forming a circular or irregular pattern, until they cover the entire leaf. The edges of the spots remain yellow. Massively infected leaves fall prematurely, especially if the infection started from their base.

Pseudocercospora: generates spots on the leaves, manifested differently depending on the pathogen species and the orchid cultivar, and can have circular to almost circular shapes, which reflects the way the fungal colony grows. Sometimes their color is purple-black, with small and numerous brown or black spots towards the inside, as the size of the spots increases. Other species of Pseudocercospora produce smaller, irregularly shaped spots, but in larger numbers. When larger leaf surfaces are affected, a general mosaic pattern is observed on the upper surface of the leaf, while the lower areas are covered with dots, represented by sporiferous bodies and which correspond to the pattern on the upper surface.

Guignardia : the first signs of infection appear as small, dark purple, elongated lesions on any of the leaf surfaces, arranged parallel to the laminar venation, taking on an elongated or rhomboid appearance. Sometimes, the adjacent lesions merge, acquiring irregular shapes, which can affect large surfaces of the leaf. With age, the center of the affected areas changes color, becoming darker, while sporiferous bodies develop inside them, having a rough texture. The disease mainly affects species of the genera Ascocentrum and Vanda, as well as their hybrids. The pathogen is also known as Phyllosticta, the name referring to a different sexual stage of the same fungus.

Phyllosticta: the spots produced can be initiated in any region of the pseudobulbs or leaves, in the form of small, yellow and slightly deep lesions. As they grow, they become round or oval, grow in depth, especially if the infection appears on the leaves. Over time, they darken in color, becoming gray or dark brown, developing a slightly raised edge, reddish to purple-black. Finally, the development of central sporiferous structures is observed. Individual spots are approximately 6.5 mm in diameter. Leaves with severe infections may drop prematurely. The installation of the disease is favored by conditions of insufficient light radiation. Phyllostachia represents a sexually different stage of the Guignardia pathogen.

Septoria : small spots can appear on any surface of the leaf, in the form of small, deep, yellowish lesions, which continue to grow, becoming brown or black, circular or irregular in shape. At the same time, they can merge, forming irregular, large-sized patterns. Severely infected leaves may drop prematurely.

Affected taxa: Cattleya, Vanda, Oncidium, Phalaenopsis.

Treatment: Dithane .

Affection: spotting of flowers

The pathogen: Botrytis

Symptoms: small spots, approximately 1 mm in diameter, on the flowers, black or light brown in color. They can increase their size and cover the entire flower. They appear in conditions of high humidity, especially if the spent flowers are left on the flower stems or in contact with the culture medium.

Affected taxa: Phalaenopsis, Cattleya, Vanda, Oncidium.

Treatment: Folpan, Dithane, Topsin.

Affection: Fusarium wilt

The pathogen: Fusarium

Symptoms: blocks the flow of liquids through the vascular system of the plants, leading to their wilting. Infected leaves turn yellow, thin, wither and wrinkle, these symptoms being followed by the death of the plant in a period of 3 to 9 weeks, in the case of severely affected plants, or, in the case of moderately affected plants, their decline can last up to a year or more. The diagnosis in the case of species of the genus C attleya is given by the presence of a ring or a discolored band, purple or purple-pink in the outer layers of the rhizome, visible when it is sectioned. In serious cases, the entire rhizome can be affected by the respective coloration, which can also extend into the pseudobulbs. Phalaenopsis and Paphiopedilum species can be infected due to too high concentration of salts, too low temperatures of the substrate, excessive watering or excess of fermented peat soil in the substrate. The roots will rot, and the bundle of the plant will be affected by a dry black rot. The deep spots on the leaf surface will enlarge, while the old leaves will become leathery and the young ones will turn red. The flower stem will develop pits with rot, eventually leading to the fall of the flowers.

Affected taxa: Cattleya, Vanda, Phalaenopsis, Epidendrum, Cochleanthes, and many other species.

Treatment: Topsin, Dithane.

Affection: black rot

The pathogen: Pythium, Phytophthora

Symptoms: initially partially translucent, later black spots, large, with a tendency to expand rapidly, affecting any organ of the plant, especially leaves and new growth. It appears especially in hot and humid seasons.

Affected taxa: Cattleya, Vanda, Phalaenopsis, Epidendrum, Cochleanthes and many other species.

Treatment: Funguran, Champ, Aliette, Dithane, Curzate Manox, Folpan .

Affection: package rot

The pathogen: Sclerotinia

Symptoms: the main symptom of parcel rot is represented by the rapid fall and rotting of the roots, pseudobulbs and the lower parts of the leaves, which turn yellow-cream, and the tissues subsequently turn brown, due to the invasion of other pathogens. Finally, the disease destroys the entire basal portion of the plants. The affected leaves turn yellow, wither and die. You will notice small, yellow or gray areas, similar to mustard seeds, located on the affected tissues, which represent the resistant forms of the fungus.

Affected taxa: Brassidium, Brassia, Oncidium, Cymbidium, Phalaenopsis, Vanda, Cattleya.

Treatment: Topsin.

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