Controlling Cochineal Mealybugs on Prickly Pear

White Spots on Prickly Pear: Cochineal Mealybug Infestation

A central Arizona gardener battles recurring white, sticky mounds on prickly pear pads. Conflicting advice suggested insects vs. fungus; the correct diagnosis is cochineal mealybugs (scale insects).

Identification

The white, cottony masses are protective coverings for the tiny insects. They feed on plant sap, weakening the cactus and potentially killing it if unchecked.

Treatment Options

• Early stage: Blast off with a strong jet of water from a hose-end nozzle.
• Moderate infestation: Scrub pads with a long-handled brush dipped in insecticidal soap or unscented dish soap solution.
• Severe infestation: Power-wash, then spray thoroughly with a mix of spectracide (or similar insecticide) and insecticidal soap. Do not rinse.
• Winter (dormant season): Apply neem oil spray per label directions; no scrubbing needed.
• Organic approach: Power-wash, then spray with neem oil + natural soap, scrub, respray, no rinse.

Long-Term Prevention

Mealybugs often live in soil. Consider starting clean pads in a new bed, or bare-root existing plants, inspect roots, and repot in fresh, sterile cactus mix. Let old soil sit fallow to starve remaining pests.

Note on Bordeaux Mix

Bordeaux mixture is a copper-based fungicide, ineffective against insects. The problem is insect, not fungal.