There are several insects that attack our yuccas, agaves, and cactus plants.
Agave snout weevil
This destructive pest bores into the base of the plant to lay its eggs. The female lays her eggs at the base of the plant. When the larvae hatch, they bore into the plant, infecting it with a bacteria. That starts rotting the plant, along with the larvae feeding on the inside. The plant soon collapses.
Right now, the only control is imidacloprid, an EXTREMELY toxic chemical that will kill everything nearby.
To help prevent it, allow space between your plants and keep things cleaned up. Avoid over watering which can stress the plant. When you suffer a loss, double bag the infected plant, secure tightly and put in the trash.
There are two species:Hesperolabops gelastops and Chelinidea sp. (also called cactus corieds)
These are sucking pests that cluster on the pads of opuntia. Control them with powerful blasts of water or a soap-based or neem oil product. However, do not spray plants with these products when temperatures exceed 85?.
Yucca plant bug
This is another sucking insect. Use the same control techniques as with cactus bugs.
Cochineal scale on cactus plants
This insect is related to mealy bugs. This is a soft scale with fluffy white covering. It may resemble tiny cotton balls all over the pads of your opuntias. But if you squish it, you release a red dye that’s been used for many years. That’s the cochineal insect itself that you squished.
Again, control with high pressure water or the soap or neem treatment. If it’s just on one or two pads, you can simply break those off, double bag them and put them in the trash.
Opuntia scale (hard scale on cactus plants)
This hard scale pest can be in really high populations on cactus plants. You may be able to scrape them off. Otherwise, use horticultural oil or soap. Again, be cautious about applying this in high heat.