Key points for pest and disease control techniques for Ligustrum japonicum 'Howardii'

Ligustrum japonicum 'Howardii' (Ligustrum sinense 'Howardii'), as a hot-selling variety of landscaping color-block seedlings in recent years, will occupy an important position in the recent engineering color-block seedling market. Ligustrum japonicum 'Howardii' is an evergreen small tree of the genus Ligustrum in the family Oleaceae, sharing the common characteristics of general privet: it prefers warmth, grows very fast under slightly acidic soil conditions, and has a high fertilizer demand during the growing period; however, it grows poorly under soil conditions that are relatively sandy and poor in fertility. Ligustrum japonicum 'Howardii' originated in Japan, so it is relatively cold-tolerant, and the lower the temperature, the more vivid the golden yellow of the new leaves. At the same time, it has strong heat tolerance, and high temperatures above 35 degrees will not affect its ecological characteristics and ornamental characteristics. Its golden-leaf period is long, with the golden leaves dominating in spring, autumn and winter, making it the golden mainstream of the future.

Pest and disease control

Ligustrum japonicum 'Howardii' shows different pest and disease damage in different regions. In this locality, the main disease is rust, which is the most serious, especially in areas with many pear trees and cypress trees around the nursery, where the many sources of infection make large-scale outbreaks likely, so sufficient attention must be paid. Reasonable placement density is an effective measure to prevent disease; generally, the placement density per mu should not exceed 40,000 pots, as excessively high density often causes outbreaks of disease. Rust is most serious from June to September, so special attention should be paid, with key control starting from May to June. Fungicides such as triadimefon, Score (difenoconazole), chlorothalonil and DuPont Fuxing can be used in rotation, applied once every 10-15 days for 3-5 applications. During control, 0.2% water-soluble fertilizer or trace-element fertilizer can be added for topdressing and supplementing trace elements to enhance the plant's disease resistance. Among insect pests, root-feeding pests such as white grubs and cutworms are the most serious, occurring around July to September. The control method is to promptly remove surrounding weeds and weeds in the pots; for severely affected areas, drench the roots with 800-fold phoxim dilution. When drenching the roots, take care to avoid high-temperature periods and maintain humidity in the pots to prevent phytotoxicity.