1. Calonectria pseudonaviculata infection
Likelihood: HighThe fungus directly infects leaves and young twigs. It produces characteristic lesions and fruiting bodies when conditions are wet, and it can kill foliage quickly under favorable weather.
Identification
- remove_circle_outlineCircular tan to brown leaf spots with darker margins; spots often develop a bleached center.
- remove_circle_outlineRapid defoliation starting on older leaves and progressing upward through the plant.
- remove_circle_outlineBlack pinpoint fruiting bodies visible on wet lesions with a hand lens or after rain.
- remove_circle_outlineTwig cankers and dieback where infected leaves fall but twigs remain symptomatic.
The Fix
- 1Remove and dispose of heavily infected plants or severe sections-bag and burn where allowed, or send to municipal green-waste if permitted.
- 2Sanitize pruners and tools between cuts with 10% bleach or 70% alcohol to avoid moving spores.
- 3Avoid overhead irrigation and schedule watering for early morning so leaves dry before nightfall.
- 4Apply fungicides as a protectant on healthy plants during warm, wet periods and follow local extension label guidance for frequency and timing.
- 5Quarantine new boxwood purchases and inspect for leaf spots for at least 2-4 weeks before planting them near existing shrubs.