What's eating my sweet orange?

Sweet orange (Citrus sinensis) hosts a wide range of pests. Citrus leafminer is the most visible on young trees, disfiguring flush growth. Scale insects and soft scales coat branches and fruit, producing honeydew that fuels sooty mould. Aphids weaken new growth and spread citrus tristeza virus. Spider mites cause silvering in hot dry spells.

Larvae tunnel silvery, serpentine trails through new leaf flushes; affected leaves curl and harden; opens entry wounds for citrus canker bacteria Time sprays of neem oil or spinosad to coincide with new flush emergence; encourage parasitoid wasps (Ageniaspis citricola); mature trees tolerate damage with little yield loss

Encrusted bark, stems, and fruit; sap removal weakens the tree; heavy infestations produce copious honeydew that coats leaves in black sooty mould Apply horticultural oil (white oil) in spring; introduce or conserve natural enemies (Aphytis spp. parasitoid wasps); control ants with sticky tape barriers, as ants protect scales from predators

Colonies on young shoot tips cause curling and stunting of new growth; transmits citrus tristeza virus (CTV), a serious disease of sweet orange Spray new flushes with insecticidal soap or neem oil; conserve parasitic wasps; healthy mature trees tolerate low populations without treatment

Silvery-grey stippling on upper leaf surfaces; fruit russeting; worst in hot dry summers; can cause premature leaf drop on stressed trees Apply horticultural oil or miticide (abamectin); introduce predatory mites (Phytoseiidae); ensure adequate irrigation to reduce heat stress