What is Cactus Scab?
Cactus scab is particularly common on prickly pear cactus but can affect many other varieties. It is a form of edema, where something has stimulated an abnormal increase in the size of the cells. This results in strange patches on the skin of the plant. It occurs in many other plants too, such as:
Tomatoes Cucumbers Potatoes Begonia Violets Cabbage
Cracks, discoloration, dry scabby lesions? Identifying the issue is quite easy, although the appearance can be mistaken for sunscald or spider mite attacks. Initial signs of scab of cactus are pale yellow spots on the skin of the plant. These become irregular, corky, or rusty. Hence, the name corky scab. The whole effect looks like the cactus has a patch of eczema. Essentially, the cells in the epidermis are breaking and opening up, resulting in almost wound-like lesions. The oldest parts of the plant are usually the first to show signs, with young shoots rarely being affected until they mature. Some plants experience just a few patches, while others can become covered in them.
What Causes Corky Scab on Cactus?
It is believed to be caused by poor cultivation methods and once noted, can be halted before it damages any more of the plant. Corky scab on cactus is primarily an aesthetic disease, but it can have an economic impact on commercial growing. Luckily, the problem is easy to prevent by changing cultural methods. As one of the more common diseases of cacti, corky scab is thought to be the result of overwatering, low temperatures, and poor ventilation. It is most common in areas where there is abundant warm water in the soil and cool, moist temperatures. Other situations thought to stimulate the disease are high light, injury to the plant, chemicals, and poor drainage. Since most of these conditions can be controlled, cactus scab treatment relies upon changing the cultural situation and methods. Outdoor plants may need to be moved to a location where more control over wind, temperature, and ambient humidity is possible.
Cactus Scab Treatment
There are no sprays, drenches, or systemic preparations for cactus scab treatment. Avoid irrigating in cool, moist weather and ensure good drainage is occurring. Never let a cactus sit on a saucer in water. If plants are indoors or in a greenhouse, increase ventilation. Increase the temperature of the area in which the plant is being grown. Avoid fertilizing in fall and winter, and do not use a formula with high nitrogen content. Keep light bright but not above 14,000-foot (4,267 m.) candles, or lumens. If necessary, repot the plant into a fresh cactus mixture. Generally, going back to good cactus cultivation and ensuring good light, watering practices, and diminishing humidity will prevent any further corking and see your plant back on the road to optimum health.
