Control Methods for Common Diseases and Pests of Golden Privet

The diseases commonly affecting golden privet mainly include: leaf spot, ring rot, and sooty mold. The main pests include: scale insects and white grubs.

Brown spot disease

Brown spot disease is the most serious leaf spot disease of privet and is caused by pathogenic fungi. In the early stage of the disease, small brown spots appear on the leaves, surrounded by purplish-red halos, and black mold-like substances are visible on the spots. As the temperature rises, several spots sometimes merge together, and eventually the leaves wither and fall off. The optimum temperature range for the growth of this pathogen is 25°C to 30°C, and the optimum temperature for spore germination is 18°C to 27°C. Under suitable temperature and high humidity conditions, the spores can germinate within a few hours. After the rainy season begins, if plants are densely planted and ventilation and light penetration are poor, a relatively stable environment with high humidity and suitable temperature forms among the plants, which is very favorable for the germination and invasion of pathogen spores, and the pathogen can infect repeatedly. If not taken seriously, the disease may occur on a large scale. When the disease occurs, a large number of leaves fall off, seriously affecting the landscape. Spray 1000 times diluted carbendazim solution or 1200 times diluted ethirimol solution.

Sooty mold

The occurrence of sooty mold is mainly induced by the secretions after damage by scale insects. After being damaged, the plants, leaves, and branches are covered with black soot-like substances, and leaf photosynthesis is inhibited. In addition, the branches, trunks, and leaves of the whole plant are all damaged. The control method should combine pest and disease treatment: spray a mixture of 50% thiram wettable powder at 600 times dilution plus 40% omethoate emulsifiable concentrate at 800 times dilution.

Comstock mealybug

Also known as the mulberry mealybug. The female adult is about 5 mm long and about 3 mm wide, with a flat oval body, pink in color, and the body surface covered with white waxy powder; the nymph is oval, flat, light yellow, and also covered with white waxy powder on the body surface; the egg is oval, light yellow, and the egg sac is white and cotton-like. Dozens of eggs gather into masses. It has 3 generations per year. The peak occurrence period of the first-generation nymphs is mid-to-late May, the peak occurrence period of the second generation is mid-to-late July, and the peak occurrence period of the third generation is late August to early September. It sucks plant sap, causing branches and leaves to lose water and wilt, and in severe cases the whole plant shrinks and dies. It can also induce sooty mold.

In autumn and winter, clean up dead branches and fallen leaves and burn them in a centralized manner to kill overwintering eggs or female insects among them. Chemical control is most effective during the peak hatching period of eggs or the first-instar nymph stage. Spray 1000 to 1500 times diluted solution of methidathion or chlorpyrifos once every 5 to 7 days, and use it continuously 2 to 3 times to completely eliminate them. When spraying, be sure to spray the whole plant (each time you spray, do not only spray the leaf surface; the spray gun should pass through the surface leaves and reach the branches and trunk), so as to achieve a good control effect.

White grubs

White grubs damage the root system of golden privet seedlings planted for more than two years, biting and feeding on the capillary roots and the epidermis of the main roots, causing root necrosis and rot, and sometimes leaving only the surface capillary roots on the plant, resulting in poor water absorption capacity. After the root system is damaged, once high-temperature weather occurs, the whole plant wilts, and in severe cases it dries up and dies.

During the damage period, use poisoned bait to trap and kill them. Mix 0.5 kg of phoxim with 0.5 kg of water and 15 kg of half-cooked seeds or other bait materials, and evenly scatter it on the seedbed at night during the damage period. Or drench the roots with 1000 times diluted phoxim. Phoxim has strong photodegradation, so it is best applied at night or buried in the soil.

For the prevention and control of diseases and pests of golden privet, in addition to strengthening plant maintenance and management, rational fertilization, and scientific watering to enhance plant growth vigor and disease and pest resistance, the following points should also be noted: for diseases, adhere to "treat when diseased, prevent when healthy." At the same time, during the growing season, try not to prune heavily. If pruning is necessary for uniformity, then after pruning, spray a protective solution such as 1500 times diluted mancozeb or 1000 times diluted carbendazim once every 5 to 7 days. Spray continuously 3 to 4 times. In hot and humid seasons, also spray a fungicide once a week to prevent diseases; for pests, combine winter pruning with cleaning up residual branches and dead leaves, and eliminate adults to avoid a large occurrence of nymphs in the following spring.