Pest Problems Pests can be controlled by chemical insecticides or, in greenhouses, often by natural predators. Systematic insecticides are absorbed into the plants sap, poisoning any insects that are feeding on the plant and are more efficient than a contact application. Use a systematic insecticide 2-3 times during the growing season as a preventative measure even if your cactus is not infested. In addition to the pests, roots are also eaten by mealybugs, which leave powdery white deposits along roots. To save the infested plant, stand its root ball in a bath of soapy insecticide, then allow it to drain.
Brown dots are a sign of spider mite attack on young growth.
The tiny, yellow, red, or brown mites resemble ground pepper, thrive in dry greenhouses, and spine fine webs. Spider Mites are extremely small, therefore a magnifying glass is needed to clearly see them. Do not confuse Spider Mites with a harmless red mite which is much larger. These mites can be best controlled using a miticide. They usually appear on the stems and lower leaves of an indoor or greenhouse plant, and migrate up the stem.