Cause Leaf spots of Aucuba have been a common problem sent into the OSU Plant Clinic. A wide variety of fungi have been isolated and many have been considered secondary invaders (such as Pestalotia sp.) to abiotic issues such as sunburn. The fungi Colleotrichum gloesporeiodes and a Phomopsis sp. have been found by the OSU Plant Clinic and reported from WA.
Symptoms Leaf injury to Aucuba generally turns black and spots may be of many sizes. Phyllosticta aucubae infection results in brown or black zonate spots along the margin of leaves with small, black fruiting bodies (pycnidia). Defoliation may also occur.
Not to be confused with yellow spots and blotches that are normal for most cultivars of the Gold-dust (variegated) type. Winter injury will cause lower older leaves to turn brown to black and fall off.
Cultural control
- Remove and destroy infected plant parts.
- Avoid overhead irrigation that keeps leaves wet for extended periods of time.
- Plant in shaded areas for this shade loving plant.
- Protect from full sun exposure.
Chemical control
- Mancozeb-based products. Group M3 fungicides. 24-hr reentry.
- Fore 80 WP at 1.5 lb/100 gal water plus a spreader-sticker.
- Protect DF at 1 to 2 lb/100 gal water plus 2 to 4 oz
spreader-sticker.
Reference White, R. P. 1935. Pestalotia spp. on Aucuba, Cibotium and Leucothoë. Mycologia, 27:342-346.