Black spot disease

Blackspot [ Phytopathology ]
Black spot disease, Black rot

Dictionary of botanic terminology - index of names

Any of several fungous diseases of plants that produce small black spots on the leaf or stems of many plant species.

Black-spot disease of stapeliads [ Phytopathology ]

A common fungal disease which principally affects succulent Asclepiadaceae , it can cause serious damage, and plants may succumbs to it (especially seedlings)

Black spot looks exactly what the name describes. The surface of the plant will develop blackish areas on the epidermis. Depending on the type of rot, these spots may be either wet or dry and may extend underneath the dermal surface. Wet rots are much more serious than dry rots. One of the more common wet rots is caused by phytophthora, a fungus. If these show up, it is best to discard the plant and start over. Because this disease can be spread in contaminated soil, it is best to throw the whole pot in the trash. Don’t think to recycle the potting soil it will simply spread the disease to other plants.

This diseases are due principally to inadequate cultural conditions like low winter temperature, poor ventilation, overwatering and excess of nitrogen. Plants are particularly at risk during the overwintering ( when most of the plants don’t tolerate temperature under 10°C) and some species proved to be very problematic (Tavaresia spp., Hoodia spp., Larryleachia (Trichocaulon) spp.) sometimes even during the growth season.

Prevention and cultural disease control is the most important step in reducing this problem as there is no an effective treatment, anyway when black rot is seen at an early stage it is possible to try to recover the plants removing and disposing carefully the affected parts and placing the plant in quarantine.
Reduce water applications to any plants suspected of stem rot disease and be sure to start with fresh potting medium, pots and pathogen-free cuttings for each crop.

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Holdfast roots [ Botany ]
Dictionary of botanic terminology - index of names

Some species of climbing plants develop holdfast roots which help to support the vines on trees, walls, and rocks. By forcing their way into minute pores and crevices, they hold the plant firmly in place.

Climbing plants, like the poison ivy (Toxicodendron radicans), Boston ivy (Parthenocissus tricuspidata), and trumpet creeper (Campsis radicans), develop holdfast roots which help to support the vines on trees, walls, and rocks. By forcing their way into minute pores and crevices, they hold the plant firmly in place. Usually the Holdfast roots die at the end of the first season, but in some species they are perennial. In the tropics some of the large climbing plants have hold-fast roots by which they attach themselves, and long, cord-like roots that extend downward through the air and may lengthen and branch for several years until they strike the soil and become absorbent roots.

Major references and further lectures:
1) E. N. Transeau “General Botany” Discovery Publishing House, 1994