Citrus Greening (HLB)
Candidatus Liberibacter asiaticus
Symptoms
Blotchy asymmetric yellowing (mottling) of leaves that does not match across the midrib. Fruit stays small, lopsided and stays green at the base with bitter taste; trees decline and die over a few years.
Prevention
Plant only certified pathogen-free seedlings and control the citrus psyllid vector aggressively. Remove and destroy infected trees immediately — they are a reservoir for spread.
Treatment
Organic
There is no cure. Manage the psyllid vector with neem oil and natural predators (ladybugs, parasitic wasps) and maintain tree vigour with balanced nutrition.
Chemical (last resort)
No chemical cures HLB. Suppress the psyllid vector with imidacloprid (soil drench on young trees) or foliar spirotetramat; rotate groups and observe PHI.
Affects 2 crops
Sources
MARDI Citrus Production Guide; DOA Plant Quarantine Bulletin