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Common
Disease and Disorders with the Gold-Dust Plant Aucuba japonica
Ornamental Disease Note No. 21 Tom Creswell, Plant Pathologist Mike Benson, Plant Pathologist |
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Aucuba
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.
Root Problems
 Crown rot of aucuba. Note the white fungal grown at the base and small round, tan sclerotia. |
Crown 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. |
| Root 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. |
 The above ground symptoms for root rot caused by Phytophthora sp. and crown rot caused by Sclerotium rolfsii are similar. |
| Several
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. |
 Roots of aucuba displaying galls caused by root knot nematodes. The root system is poorly developed and beginning to show signs of decay. |
Foliage ProblemsPrevention 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 diseased.
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.
Control of Foliar Problems
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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Recommendations
of specific chemicals are based upon information on the manufacturer's
label and performance in a limited number of trials. Because environmental
conditions and methods of application by growers may vary widely, performance
of the chemical will not always conform to the safety and pest control
standards indicated by experimental data. All recommendations for pesticide
use were legal at the time of publication, but the status of registration
and use patterns are subject to change by actions of state and federal
regulatory agencies.
Published by the North Carolina Cooperative Extension Service
Distributed in furtherance of the Acts of Congress of May 8 and June 30,
1914. Employment and program opportunities are offered to all people regardless
of race, color, national origin, sex, age, or disability. North Carolina
State University at Raleigh, North Carolina A&T State University, U.S.
Department of Agriculture, and local governments cooperating. 5/94/200