Scale Insects
This problem spreads through handling, insects or soil rather than the weather, so there is no live forecast risk — focus on prevention below.
When it strikes
About
Scale insects are immobile sap-suckers that attach to stems and leaves of fruit trees, citrus, houseplants and shrubs under protective waxy shells, slowly draining vigour.
Symptoms
Small brown, tan or white bumps along stems and leaf veins that do not rub off easily; yellowing leaves, dieback, sticky honeydew and sooty mould.
Organic Treatment
Scrape off light infestations, dab with rubbing alcohol, and spray horticultural oil to smother crawlers and adults. Encourage parasitic wasps and ladybirds.
Chemical Treatment
Horticultural oil timed to the crawler stage, or systemic insecticide for severe woody-plant infestations.
Prevention
Inspect new plants, prune out heavily infested wood, apply dormant oil to fruit trees, and keep plants healthy and unstressed.