Troubleshooting
Common box problems — and how to fix them
Common box (Buxus sempervirens) is generally forgiving once you match its basics, but a few issues come up again and again. Here is what each one looks like, why it happens, and the fix.
Box blight (Cylindrocladium/Pseudonectria)
Tan-coloured leaf spots, rapid defoliation, and black stem streaking, usually in wet summer conditions. Remove all fallen leaf debris which harbours spores, disinfect tools between cuts, and apply a triazole fungicide (e.g., tebuconazole) protectively. Badly affected sections should be removed and disposed of — not composted.
Box tree moth (Cydalima perspectalis)
Invasive pest across Europe (first UK record 2011, now widespread). Green-and-black caterpillars strip foliage and leave a webbing. Check for eggs (flattened, pale-yellow clusters on leaf undersides) from April. Treat with Bacillus thuringiensis var. kurstaki (Btk) biological spray every 2 weeks during larval activity or use a pheromone trap system.
Box psyllid
Tiny sap-sucking insects cause cupped, pale-green new shoot tips ('rosette' distortion) from April to June. The damage is cosmetic and plants recover fully after clipping. No chemical treatment usually needed; clip off affected shoot tips.
Prevent common box problems before they start
Most common box issues are care-mismatch, not bad luck. Dial in the basics:
Looking for common box in general rather than its problems? Read the full common box care guide — light, water, soil and feeding.
Common box problems — FAQ
Why is my common box box blight (cylindrocladium/pseudonectria)?
Tan-coloured leaf spots, rapid defoliation, and black stem streaking, usually in wet summer conditions. Remove all fallen leaf debris which harbours spores, disinfect tools between cuts, and apply a triazole fungicide (e.g., tebuconazole) protectively. Badly affected sections should be removed and disposed of — not composted.
Why is my common box box tree moth (cydalima perspectalis)?
Invasive pest across Europe (first UK record 2011, now widespread). Green-and-black caterpillars strip foliage and leave a webbing. Check for eggs (flattened, pale-yellow clusters on leaf undersides) from April. Treat with Bacillus thuringiensis var. kurstaki (Btk) biological spray every 2 weeks during larval activity or use a pheromone trap system.
Why is my common box box psyllid?
Tiny sap-sucking insects cause cupped, pale-green new shoot tips ('rosette' distortion) from April to June. The damage is cosmetic and plants recover fully after clipping. No chemical treatment usually needed; clip off affected shoot tips.