Prickly pear cacti, also known as Opuntia, are lovely cactus plants that can be planted in an outdoor desert garden or kept as a houseplant. Unfortunately, there are several common diseases that can attack these beautiful plants. One of the most serious diseases that affects prickly pear is cactus sunscald.
What is Cactus Sunscald?
So, what is cactus sunscald? Despite the name, cactus sunscald disease is not a result of sun exposure. It is actually a disease caused by the fungus Hendersonia opuntiae. This fungus infects the cladodes, or cactus pads, which are the thickened, flattened, green stems of Opuntia cacti.
Cactus sunscald disease first causes discoloration and cracking in a localized area of one cladode, then gradually spreads. This eventually causes the entire cactus to rot.
Signs of Cactus Sunscald Disease
Cactus sunscald is common, so it is important to recognize the signs. The problems begin when a small, circular, greyish-brown spot appears on one of the cactus pads. The discolored area may also be cracked. The infected area will later expand across the cladode, and the outer portion may turn reddish-brown. Finally, the entire cactus will rot. Once cactus sunscald begins to attack a cactus, other fungi may also take advantage of the infection and begin growing in the damaged area.
Mycosphaerella fungi can also cause a similar disease, also known as sunscald or scorch, on prickly pear cacti. This disease causes similar symptoms and will also eventually kill the cactus.
Sunburn on cactus can appear similar to cactus sunscald, but the affected area will appear yellowish or white and will not appear to be gradually spreading from a small original area. Sunburn can be prevented by shielding the cactus from intense sun. As long as the sunburn is not severe, it will not kill the plant.
Cactus Sunscald Treatment
Unfortunately, treating cactus sunscald is difficult or impossible. There is no cure, and infected plants usually cannot be saved. If you have more than one Opuntia cactus, focus on preventing the disease from spreading to the healthy plants.
The first step it to recognize the disease and to distinguish it from a sunburn. If your cactus does have sunscald, you should remove and dispose of the infected cactus as soon as possible to prevent the disease from spreading to healthy plants.