Why Does My Cactus Have Black Holes?

Saguaros and Nesting

• Holes in saguaros are more likely to occur and be noticeable than in other, smaller plants. A prime cause of these holes is that saguaros make ideal nesting spots for a variety of birds, including woodpeckers, hawks and owls. These holes can be life threatening to the cactus if they are too deep, but as often as not the nests are not deep enough to put the cactus in any real danger.

Saguaros and Feeding

• You may find smaller black holes in your saguaro. These may be the nesting grounds for larvae of a variety of beetles and other insects. In a large cactus, these holes are harmless. However, gila woodpeckers frequently dig into saguaros in search of food, making small holes larger, though usually still not threatening to the cactus. Woodpeckers in search of food are the prime cause of holes in saguaro cacti.

Black Holes in other Cacti

• Smaller ornamental cacti in the home or outside may also have small black holes in them. These plants are too small to be nesting grounds or even hunting grounds for birds or other larger animals, but a variety of insects will bore into a smaller cactus, regardless of the state of the plant's health, to make a home there. These holes are generally created by very small populations of very small insects, and though cosmetically less than pleasing, a cactus being inhabited by insects like these should remain otherwise healthy.

Rot

• If your cactus is developing black holes that appear wet or slimy, it may be getting overwatered and suffering from rot. Water your cactus less, usually once every week or two will suffice. If the problem appears to be growing, you may want to cut out the part of the cactus that is rotting to save the rest of the plant.