Mealybugs
White, cottony insects that hide in leaf joints and under leaves, weakening plants and spreading easily to neighbours.
Also known as: Mealy bugs
Symptoms and identification
White, fluffy or waxy clumps in leaf axils, along stems, under leaves and sometimes on roots. Leaves turn yellow and drop, growth slows, and sticky honeydew with black sooty mould may appear. Heavily infested hibiscus buds drop before opening.
Causes
Mealybugs usually arrive on a new plant or cutting. They thrive in warm, sheltered spots, and their waxy coating protects them from many sprays. Overfeeding with nitrogen and ants that farm them make outbreaks worse.
Organic treatment
Dab small groups with a cotton bud dipped in 70% isopropyl alcohol. Then spray the whole plant with insecticidal soap or neem oil, paying attention to leaf joints. Repeat weekly for at least three to four weeks, because eggs hidden under the wax keep hatching. Cut off and bin badly infested shoots.
Prevention
Keep new plants apart for two weeks and check them closely before placing them with others. Look into leaf joints and under leaves regularly, especially on hibiscus and houseplants. Remove fallen leaves and avoid overfeeding.
Chemical treatment (use with care)
For persistent infestations on ornamental plants, a systemic insecticide labelled for mealybugs can be used according to the label. Do not use systemic products on herbs or plants you eat.