How to Diagnose Cactus Pests

Walk around your cactus plant looking for a line of ants. Ant infestations are often the cause of nutrient sucking pest problems. Nutrient sucking pests such as aphids, whiteflies and scales produce a substance called honeydew that ants love to eat.

Feel the container or any smooth part of the cactus. Honeydew coats anything that nutrient sucking pests crawl past. To treat your nutrient sucking pest problem, remove honeydew and reduce your ant infestation, spray your cactus plant with an insecticidal soap.

Lift up your pot to see if there are slugs or snails crawling underneath. Snails and slugs are treated with metaldehyde bait applied to the soil. Water the soil after applying the bait.

Pull your cactus out of its container to inspect its root system if you see discoloration on the base of the plant. Root rot is a fungal disease that often occurs from over watering. Black mushy roots and cactus base discoloration are indicators of root rot. Cut out the discolored portions of the cactus with bypass shears or a sharp knife and apply a fungicide that contains sulfur. Replant the cactus.

Examine cactus leaves for white and yellow spots that indicate thrips. Thrips are insects that suck the nutrients from leaves. Apply a miticide or solution of nicotine sulfate to treat thrips problems.