Mealy Bug & Root Mealy Bug
Mealy bugs are small, woodlouse-like insects, about ⅛ inch (2-3mm) long, with a white waxy coating. They create a woolly nest to lay their eggs, and harm plants by sucking sap from the leaves, stems, and roots. There are two primary types: one that targets the foliage, and the root mealy bug, which lives in the soil and attacks the plant's roots. Root mealy bugs are harder to detect as they live beneath the soil's surface. To determine if your plant has a root mealy bug infestation, you must remove it from its pot. Presence of these pests is indicated by little white patches inside the pot and the mealy bugs on the plant's roots. 

Treatment: Remove the bugs and the wool using a small paintbrush dipped in methylated spirits. Then spray with a contact insecticide, or for really woolly plants you can water systemic insecticide into the soil. Repeat after 7 days.

For Root Mealy Bugs, remove all of the soil from the roots and wash them in a solution of contact insecticide. Allow to dry completely for two to three days before repotting into a clean pot with fresh compost. Do not water for two weeks.

Red Spider Mite
Red Spider Mites are tiny little creatures almost invisible to the naked eye. They are actually sap sucking mites, and not spiders as the name suggests. They thrive in warm and dry conditions. Indications of an infestation are evident by brown patches on the plant body, which can lead to permanent scarring. These tiny mites spread quickly through collections. 

Treatment: Since the pest is a sap-sucker, the use of a systemic insecticide is the best means of defence. Contact insecticide can also be used directly onto the mites. They seem to have a strong resistance to contact insecticide, so it's important to check the insecticide you're using specifies Red Spider Mite. Repeat every two weeks for the next three months, then treat two to three times a year as a preventative measure.

Scale Insect
These are tiny insects inside a waxy scale. They appear as small round brown patches with a raised centre. 

Treatment: Spray with a contact insecticide or water the soil with a systemic insecticide. After a coupe of days you can pick off the scales from the plant. Scale Insect is unsightly but not usually fatal.

Aphids (Greenfly)
Aphids are small insects that feed on plants by sucking out their sap. They are known for their ability to reproduce quickly and can cause significant damage to plants if left untreated.

Treatment: If you suspect that your cactus has aphids, it is important to take action to prevent further damage. One effective method is to physically remove the aphids from the plant. You can do this by gently wiping them off with a cotton swab dipped in soapy water or by using a stream of water to dislodge them from the plant. Alternatively, a contact insecticide can be used.

Sciarid Fly (Fungus Gnats)
The adult fly is very small with an erratic flight pattern, often found near plants. These insects scurry across the compost surface and quickly hide when threatened. They prosper in damp environments, laying eggs at the plant's base. The eggs hatch into tiny, nearly transparent larvae that primarily consume decaying organic matter. However, cactus sciarids also attack the plants, burrowing into the base and moving upward, leaving behind a hollowed-out plant. The moist conditions ideal for seed germination are also perfect for these pests, and an infestation can swiftly devastate young seedlings.

Treatment: While repeated spraying with contact or systemic insecticides can safely control the adult flies, the larvae within the compost present a greater challenge. Applying systemic or contact insecticides directly into the compost is the most effective method of eradication.

Thrips
For cactus and succulent growers, Lithops are particularly susceptible to Thrips (Western Flower Thrips or WFT). These pests are tiny, only 2–3 mm in length, with mouthparts designed to scrape and puncture plant tissue. They feed on the sap that oozes from these wounds and also consume pollen, often residing in flower heads. While Thrips may not seem to cause significant harm to cactus and succulent flowers, they can severely disfigure Lithops. These insects tend to infiltrate the new growth, especially when Lithops are blooming. They gather within the flowers to feed on pollen and also damage the soft tissue of the emerging plant body. The damage may not be noticeable during the flowering period and might only become evident the following year when the new growth appears.

Treatment: Controlling this insect is challenging due to its variable life cycle, which includes numerous stages which accelerates with rising temperatures. Systemic insecticide applications, carefully timed over roughly three weeks to cover one insect generation, should maintain control. However, if additional spraying is needed later, a different insecticide must be used to avoid the pests developing immunity to the product.