Disease and Disorders with the Gold-Dust Plant Aucuba japonica
Ornamental Disease Note No. 21
Creswell, Plant Pathologist
Mike Benson, Plant Pathologist
japonica, the gold-dust plant, is commonly planted in the landscape
of North Carolina. It grows best in part shade. Aucuba may be affected
by several diseases and cultural problems that limit successful cultivation.
rot of aucuba. Note the white fungal grown at the base and small
round, tan sclerotia.
rot, caused by the soil-borne fungus Sclerotium rolfsii, is
a widespread problem of aucuba but occurs infrequently. Additional
hosts include ground covers like ajuga, perennials, bedding plants,
and many other woody ornamentals and trees. In the vegetable garden,
tomatoes, peppers, and carrots are hosts, just to list a few. The
fungus attacks and kills plants at the ground level when humid conditions
resulting from a tight plant canopy or debris near the stem persist.
Eventually, the black decay (necrosis) may extend several inches upwards
in the stem. White fungal growth and sclerotia (small round, tan to
brown over-wintering structures of the fungus about the size of a
BB), are often seen at the base of diseased stems. Foliage of affected
plants wilts and the plant dies quickly. This fungus can attack both
large and small plants. Remove infected mulch near plants and replace
with a 1-2" layer of new mulch.
rot of aucuba is caused by the soil-borne fungi Phytophthora cinnamomi
and P. citricola. Above ground symptoms are similar to crown
rot, however, the roots are usually more extensively rotted, white
fungal growth and sclerotia are absent, and decay may not extend as
far up the stem. Diseased plants eventually die.
above ground symptoms for root rot caused by Phytophthora
sp. and crown rot caused by Sclerotium rolfsii are similar.
nematodes cause root damage to aucuba. The root-knot nematode (Meloidogyne
sp.) is the most common and causes the development of galls on the
naturally thick aucuba roots. These and other nematodes reduce vigor
and growth, as infected plants cannot take up water or fertilizer
as well as healthy plants.
A nonpathogenic root rot may also develop on aucubas growing in soil
very high in organic matter and soil that is poorly drained. Excess
fertilizer placed too close to the crown of the plant can also cause
stem or root injury.
of aucuba displaying galls caused by root knot nematodes. The root
system is poorly developed and beginning to show signs of decay.
of Root Problems
Purchase plants from a reputable nursery. If possible, examine roots
and stems of plants for decay. A well-watered but wilted plant may be
Have soil from the planting bed tested for nematodes before planting
(send samples to the NCDA-Nematode
Advisory Section). If soil tests indicate that nematodes are a problem,
the planting area should be avoided.
Set aucubas in well-drained areas in raised beds with a mixture of soil
and 1/2" pine bark if soil is heavy clay. Do not plant aucuba were
aucubas, azaleas or rhododendrons have died before.
Do not plant deeper than the soil level in the container.
Fertilize only lightly, spreading it evenly over the root zone.
Mulch is fine but keep it about 6 inches away from the main stem.
Foliage problems, such as wilting or necrotic spotting, may reflect a root
problem or other stress condition. Aucubas grow best in shaded areas. Plants
growing in exposed areas may develop black leaf spots or blotches. A dieback
characterized by total decay of leaves, petioles, and branches often occurs
on exposed plants in early spring. This can be caused by exposure to full
sun combined with cold injury. A weakly pathogenic fungus (Botryosphaeria
sp.) is often found in such tissue and is common on many woody ornamental
plants under environmental stress.
Significant dieback is often a sign that the plant may be under stress from
root rot, crown rot, nematodes or other factors.
Plant aucubas in partially shaded areas. Give exposed plants some protection
during cold winter weather. Promptly prune out dead branches several
inches below any sign of discoloration. Avoid excess fertilizer, especially
during late summer and fall.
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