Common problems with cactus and succulents

Damaged by the Agave Snout-nose weevil

Cactus and succulents are relatively problem free, as long as growing conditions, soil, drainage and sun orientation are correct for the species. Always make sure you are purchasing plants are suitable for both the heat and cold. Not all of these plants can handle the brutal low elevation summer heat, or temperatures dipping into the teens. When in doubt: Plant natives!

Cochineal scale is relatively common on prickly pear and cholla. It is evidenced by cottony-like spots on the pads and stems. This insect sucks out nutrients. If left without treatment, it will eventually kill the plant. Control is simple by using repeated hard sprays of water. It’s important to catch this early, however. If the entire plant is covered with the white substance, it’s unlikely you’ll ever be able to get rid of it. It’s been to remove and replace the plant. As a side note, the female of the insect that causes the white cottony mass is the source of a red dye known as cochineal red. The red dye is used in clothing and candy, so if you are vegetarian, think twice about eating candy dyed red!

The cactus longhorn beetle attacks some columnar cactus and prickly pears leaving chewed areas on the uppermost parts. It is identified by very long antennae, as long as the beetle itself. Hand picking is considered the best control method, so you’ll need to be vigilant. The larvae will eat the inside of the plant, so they are hard to detect and control before the plant is dead.

Sahuaro rot (bacterial necrosis), is an infection caused by a number of things. It can result from sunburn, injury (including transport to planting site), frost damage, too much water and poor drainage. Bacteria spreads inside the plant before you notice what is happening. When a black, odorous liquid oozes out of the plants epidermis, it is too late to save. If this appears on an arm, removal of the arm may save it, but it must be caught before the rotting spreads into the main stem.

And what about those holes in sahuaros made by birds? Birds and sahuaros have lived harmoniously together for centuries, so trust me, the sahuaro will be fine. Those holes, usually made by woodpeckers, will later become homes for other critters, including bats and the tiny pygmy owl.

Some agave species are attacked by the agave snout-nose weevil. You’ll know you’ve got them if the leaves of the agave are laying flat on the ground. This insect prefers stressed plants (think thirsty, overwatered, too much sun, too little sun, poor drainage, temperatures too hot or too cold) and seems to prefer the Century Plant, one of the largest of the agave species. Infestation is hard to detect, and by the time the plant wilts it is too late. Remove, dig up the weevil, and kill it before replanting.