Aucuba japonica, a member of the dogwood family, is also commonly known as the "gold-dust plant," "gold spot aucuba" or "Japanese aucuba." This evergreen shrub is enjoyed for its foliage, showy fruits and an ability to thrive in shaded or partially shaded areas. Although the Japanese aucuba is relatively pest- and disease-free when properly maintained, it is still susceptible to being attacked by a few pests.
The Japanese aucuba may be attacked by certain species of aphids, small insects that use a piercing mouthpiece to penetrate plant tissue and feed on fluids. A small aphid population will cause minimal damage to plants, but a large population can cause leaf distortion and yellowing and stunt growth. Aphids also excrete a sticky substance known as honeydew, which hosts the sooty mould fungus and negatively impacts the aucuba's appearance. Aphids rarely warrant serious control efforts. Maintaining healthy levels of aphid predators like certain wasps, lacewings and lady beetles will keep aphids in check. A strong spray of water will knock the aphids off the plant. If necessary, apply insecticidal soap, neem oil or a narrow-range oil to control this pest.
Several species of scales, including the oleander scale, may infest aucuba. Scales are small, generally immobile and feed on plant fluids, but they rarely cause serious damage to plants. A heavily infested plant can suffer from leaf yellowing, distortion and premature drop. A problematic scale presence can be addressed using thorough applications of horticultural oil when the scales are still in their crawler stage. Plants that are properly cared for will typically withstand a scale problem easily.
Mealybugs are soft-bodied, wingless, light-coloured insects less than 1/5 of an inch long that may be a problem for aucuba in some areas. Mealybugs generally group in large numbers, appearing as white, fluffy masses. A heavy infestation can slow plant growth and cause leaf drop. Treat for mealybugs by maintaining plant vigour with proper care practices. If necessary, spray the plant with water to dislodge the pests or treat the mealybugs using insecticidal soap or narrow-range oil.
Several nematode species can damage aucuba roots. Frequently, the most serious nematode is the root-knot nematode, which can cause the development of galls on roots and affect the plant's ability to absorb water and nutrients from the soil. Test the soil for nematodes prior to planting and maintain good plant health by using proper cultural practices.
Fungi such as Sclerotium rolfsii and Phytophthora can cause crown and root rot. Sclerotium penetrates and kills the plant, beginning near ground level. Rot caused by Phytophthora may not show visible decay above the soil line, but plants wilt, roots are extensively rotted and affected plants die. Remove and destroy plant debris and plant only resistant plants in the area.