Black rot; more often at Cattleya, Laeliocattleya and Laelia detectable and feared as "black-leggedness" and "falling over" in seedling cultures.
Spraying over the plants spreads the fungal spores easily. High humidity and heavy watering promote infestation. Young plants turn black overnight, if they don't dry off in time in the afternoon. They are particularly sensitive after they have been transferred to a new substrate. Large plants can usually no longer be saved, if there are dark brown to blackish rot spots on the leaves. The diseased tissue becomes soft and rotten, tissue destruction quickly spreads to bulbs and roots. If recognized early enough, cutting off the diseased parts and transferring the plant to dry ones may help, moving air. With reasonable ventilation, this phenomenon is hardly to be feared.
Focal spot diseases can be recognized by their circular or irregular shape, but sharply demarcated brown spots. They develop from millimeter size up to 2 cm in diameter or more and may cause. Death of the leaves and bulbs. The pathogens are fungi of various genera. Your reaching around is caused by excessive temperature and humidity, Light mangle, too frequent spraying with water and excessive nutrition. The spread of the disease is countered by immediately removing the diseased parts and spraying with fungicidal agents – i.e. fungicides and the creation of normal environmental conditions.
Viral diseases are still relatively rare in orchids. Black stroke disease is known (Cymbidium stroke virus) an Cymbidium. Control is initially only possible by completely destroying infested plants and keeping them free from aphid infestation, because the aphids can be carriers of the virus.
The pesticides were not mentioned by name. They are constantly being improved and perfected, and their application in orchids does not differ from the type commonly used in other plants. A marked sensitivity to certain drugs – as with other plants z. T. known – does not exist when used according to regulations.
The only problem for the orchid lover is the application of the partly. highly toxic agents in inhabited areas. Plants to be treated must be brought outdoors or in remote rooms, to exclude any danger to people. Preventive treatment at regular intervals (different depending on the pathogen) is always better than hesitation, until damage can be seen. In conclusion, it should be said in summary, that reasonable care and the most favorable environmental conditions are the best prerequisites for healthy plants.