What are the common pests and diseases of golden privet (Ligustrum × vicaryi)? A detailed guide to prevention and control methods

Golden privet is widely used in landscaping projects in northern China thanks to its easy propagation, rapid growth and tolerance of pruning and shaping. Hengshui City, Hebei Province, has been growing golden privet for more than ten years, and as the planted area and the years of cultivation have increased, its pests and diseases have become increasingly serious. Based on many years of observation and research, the author has summarized the occurrence patterns and control techniques of several of the most common and most damaging pests and diseases.

White grubs

Observation has shown that golden privet is a high-quality food source for white grubs. In plots planted with Japanese barberry (Berberis thunbergii), Japanese euonymus (Euonymus japonicus), Chinese juniper (Juniperus chinensis var. 'Hennan') and Chinese sabina (Juniperus chinensis 'Kaizuca'), only golden privet suffered obvious white grub damage, and in severely affected plots the damage often even killed plants in whole patches.

White grubs are the larvae of scarab beetles. They bite and feed on the roots of golden privet, and the above-ground parts of infested plants first appear wilted from lack of water. If infested plants have plenty of water and the ground stays consistently moist, they will not die, but their growth will be weak. In addition, the root epidermis below ground of infested plants is gnawed away, so the plants are easily pulled out, and plants with sufficient water can only grow a small number of new roots close to the soil surface.

The biological characteristics of white grubs are one generation per year, overwintering in the soil as adults or larvae. In northern China, the period from April to the end of May each year is when overwintering larvae emerge, pupate and lay eggs; May to July is the emergence and egg-laying period of the first-generation larvae; and September to November is the period of vigorous activity of the overwintering larvae.

Prevention and control methods:

(1) When planting seedlings, use compost and barnyard manure as base fertilizer, and apply them only after they are fully decomposed. (2) When the area infested by white grubs is small, pull out the affected seedlings and dig out the larvae near the root zone of the seedlings, enlarging the digging range appropriately. (3) Taking advantage of the adults' habit of playing dead, catch or shake them off the crops where they rest and kill them. Or, taking advantage of their phototaxis, use black-light lamps to trap and kill the adults. (4) When the adults are feeding and causing damage, spray 4.5% beta-cypermethrin at 1000x to 1500x dilution, 50% phoxim emulsifiable concentrate at 1000x, or 15% chlorpyrifos at 1000x and other insecticides to kill the adults; during the larval damage period, drench the root zone of the seedlings with 50% phoxim emulsifiable concentrate at 1000x to 1500x, or 90% trichlorfon at 900x to 1000x. The author's approach is to drench the plots damaged in the previous year with phoxim once in early June and again in early July; these two drenchings completely eliminate the pest.

Mealybugs

Adult and nymph mealybugs pierce and suck plant sap. In severe cases the branches and trunks are covered with the insects, causing weak growth and making the plants susceptible to sooty mold and other diseases. It is a pest that is difficult to control and causes serious damage.

Mealybugs have three generations per year and overwinter as egg sacs in the coarse bark crevices and under loosened bark of branches, in soil and stone crevices near the plants, or in fallen leaves. When the female adult lays eggs, she first forms a cottony waxy egg sac and then lays the eggs inside it. The first-generation nymphs begin hatching in large numbers from mid-to-late May, and this generation hatches relatively uniformly; the second-generation nymphs hatch in large numbers from mid-to-late July, and the third-generation nymphs hatch in large numbers from late August; the latter two generations do not hatch very uniformly. According to observations, Hengshui City suffers relatively severe mealybug damage from June to September.

Prevention and control methods:

(1) Thoroughly clear away and burn fallen leaves in winter and spring, which can greatly reduce the insect population; use a stiff-bristled brush to scrub away the egg sacs in coarse bark crevices and under loosened bark. (2) During the growth period of the first-generation pest, spray it twice at an interval of about 10 days, with remarkable results. Spraying should also be carried out during the damage period of each generation of nymphs. The insecticides used include toxicus, chlorpyrifos, and jieshijing, among others. Spray evenly, and add 0.1% neutral laundry powder when spraying to increase efficacy.

Leaf spot disease

Leaf spot disease has been the most serious disease affecting golden privet in Hengshui City in recent years, and when it breaks out it can even cause the leaves of whole patches of plants to drop. This not only affects plant growth but also deprives the plants of their ornamental value.

Leaf spot disease is a fungal disease. It overwinters as mycelium on diseased plant residues. Conidia spread through air currents or contact between branches and leaves, and invade the host through wounds and stomata. The optimum temperature for pathogen growth is 26°C, and the optimum temperature for spore germination is 18°C to 27°C. In the early stage of the disease, nearly round brown spots appear on the leaves, often with concentric rings, and the outer edge is yellow. The spots are small at first, then expand into irregular reddish-brown large spots with a grayish-white center dotted with small black dots, and in the later stage the spots merge into patches. Affected leaves drop from the branches very easily, so that in the diseased areas of golden privet the branches appear bare.

Prevention and control methods:

(1) Planting density should be appropriate and not too dense; clear away and centrally burn dead branches and fallen leaves in late winter and early spring; prune appropriately, especially with heavy pruning before spring bud break, which can effectively reduce branch density, and appropriate pruning during the growing season can effectively improve ventilation and light penetration and reduce the conditions for disease occurrence. (2) Appropriately reduce the amount of nitrogen fertilizer applied and increase phosphorus and potassium fertilizer to enhance plant resistance. (3) Spray protective fungicides such as mancozeb before the disease appears in mid-June; after the disease appears, spray 50% carbendazim wettable powder at 500x to 800x, or 75% thiophanate-methyl at 700x to 1000x, or 75% chlorothalonil at 600x to 800x and other fungicides once every 10 days, for 5 to 6 consecutive sprays, alternating the several chemicals, with remarkable control efficacy.

Fusarium wilt

Fusarium wilt is a devastating disease for golden privet. Once it occurs, almost all plants die, so prevention work is the key.

After golden privet becomes infected, the leaves wilt and droop, lose their luster, gradually lose their green color and turn yellow and withered, until the entire plant dies, while underground the fibrous roots die.

Golden privet Fusarium wilt is a fungal systemic infection disease. The pathogen overwinters in the soil and in diseased plant residues, invades through the underground roots, spreads to all parts of the plant through the vascular bundles, and multiplies within the vascular bundles, causing blockage or poisoning, which causes the plant to wilt and eventually die. After the pathogen infects the roots, the transport functions for nutrients and water are lost, so the plant suffers nutrient deficiency and then dies. High temperature and high humidity favor the occurrence of the disease, so the peak period of golden privet Fusarium wilt is from June to August each year and continues until October.

Prevention and control methods:

This disease should be prevented first, with prevention more important than cure. Strengthen cultivation management, enhance plant resistance and reduce the chance of disease occurrence. In mid-to-late May, spray fungicides preventively on key diseased areas, using protective fungicides such as zineb and mancozeb. At the same time, drench with 50% carbendazim wettable powder at 500x to 600x, or 75% thiophanate-methyl at 600x to 700x, or 75% chlorothalonil at 600x to 800x and other fungicides, drenching once every 10 to 15 days for 6 to 7 consecutive drenchings, alternating the several chemicals, with relatively good control efficacy.

Pest and disease control of golden privet

A guide to controlling pests and diseases of golden privet

 Golden privet is widely used in landscaping projects in northern China thanks to its easy propagation, rapid growth and tolerance of pruning and shaping. Hengshui City, Hebei Province, has been growing golden privet for more than ten years, and as the planted area and the years of cultivation have increased, its pests and diseases have become increasingly serious. Based on many years of observation and research, the author has summarized the occurrence patterns and control techniques of several of the most common and most damaging pests and diseases.
White grubs
Observation has shown that golden privet is a high-quality food source for white grubs. In plots planted with Japanese barberry (Berberis thunbergii), Japanese euonymus (Euonymus japonicus), Chinese juniper (Juniperus chinensis var. 'Hennan') and Chinese sabina (Juniperus chinensis 'Kaizuca'), only golden privet suffered obvious white grub damage, and in severely affected plots the damage often even killed plants in whole patches.
White grubs are the larvae of scarab beetles. They bite and feed on the roots of golden privet, and the above-ground parts of infested plants first appear wilted from lack of water. If infested plants have plenty of water and the ground stays consistently moist, they will not die, but their growth will be weak. In addition, the root epidermis below ground of infested plants is gnawed away, so the plants are easily pulled out, and plants with sufficient water can only grow a small number of new roots close to the soil surface.
The biological characteristics of white grubs are one generation per year, overwintering in the soil as adults or larvae. In northern China, the period from April to the end of May each year is when overwintering larvae emerge, pupate and lay eggs; May to July is the period of vigorous activity of the first-generation larvae; August to September is the emergence and egg-laying period of the first-generation larvae; and September to November is the period of vigorous activity of the overwintering larvae.

Prevention and control methods: (1) When planting seedlings, use compost and barnyard manure as base fertilizer, and apply them only after they are fully decomposed. (2) When the area infested by white grubs is small, pull out the affected seedlings and dig out the larvae near the root zone of the seedlings, enlarging the digging range appropriately. (3) Taking advantage of the adults' habit of playing dead, catch or shake them off the crops where they rest and kill them, or, taking advantage of their phototaxis, use black-light lamps to trap and kill the adults. (4) When the adults are feeding and causing damage, spray 4.5% beta-cypermethrin at 1000x to 1500x dilution, 50% phoxim emulsifiable concentrate at 1000x, or 15% chlorpyrifos at 1000x and other insecticides to kill the adults; during the larval damage period, drench the root zone of the seedlings with 50% phoxim emulsifiable concentrate at 1000x to 1500x, or 90% trichlorfon at 900x to 1000x. The author's approach is to drench the plots damaged in the previous year with phoxim once in early June and again in early July; these two drenchings completely eliminate the pest.
Mealybugs
Adult and nymph mealybugs pierce and suck plant sap. In severe cases the branches and trunks are covered with the insects, causing weak growth and making the plants susceptible to sooty mold and other diseases. It is a pest that is difficult to control and causes serious damage.
Mealybugs have three generations per year and overwinter as egg sacs in the coarse bark crevices and under loosened bark of branches, in soil and stone crevices near the plants, or in fallen leaves. When the female adult lays eggs, she first forms a cottony waxy egg sac and then lays the eggs inside it. The first-generation nymphs begin hatching in large numbers from mid-to-late May, and this generation hatches relatively uniformly; the second-generation nymphs hatch in large numbers from mid-to-late July, and the third-generation nymphs hatch in large numbers from late August; the latter two generations do not hatch very uniformly. According to observations, Hengshui City suffers relatively severe mealybug damage from June to September.
Prevention and control methods: (1) Thoroughly clear away and burn fallen leaves in winter and spring, which can greatly reduce the insect population; use a stiff-bristled brush to scrub away the egg sacs in coarse bark crevices and under loosened bark. (2) During the growth period of the first-generation pest, spray it twice at an interval of about 10 days, with remarkable results. Spraying should also be carried out during the damage period of each generation of nymphs. The insecticides used include toxicus, chlorpyrifos, and jieshijing, among others. Spray evenly, and add 0.1% neutral laundry powder when spraying to increase efficacy.
Leaf spot disease
Leaf spot disease has been the most serious disease affecting golden privet in Hengshui City in recent years, and when it breaks out it can even cause the leaves of whole patches of plants to drop. This not only affects plant growth but also deprives the plants of their ornamental value.
Leaf spot disease is a fungal disease. It overwinters as mycelium on diseased plant residues. Conidia spread through air currents or contact between branches and leaves, and invade the host through wounds and stomata. The optimum temperature for pathogen growth is 26°C, and the optimum temperature for spore germination is 18°C to 27°C. In the early stage of the disease, nearly round brown spots appear on the leaves, often with concentric rings, and the outer edge is yellow. The spots are small at first, then expand into irregular reddish-brown large spots with a grayish-white center dotted with small black dots, and in the later stage the spots merge into patches. Affected leaves drop from the branches very easily, so that in the diseased areas of golden privet the branches appear bare.
Prevention and control methods: (1) Planting density should be appropriate and not too dense; clear away and centrally burn dead branches and fallen leaves in late winter and early spring; prune appropriately, especially with heavy pruning before spring bud break, which can effectively reduce branch density, and appropriate pruning during the growing season can effectively improve ventilation and light penetration and reduce the conditions for disease occurrence. (2) Appropriately reduce the amount of nitrogen fertilizer applied and increase phosphorus and potassium fertilizer to enhance plant resistance. (3) Spray protective fungicides such as mancozeb before the disease appears in mid-June; after the disease appears, spray 50% carbendazim wettable powder at 500x to 800x, or 75% thiophanate-methyl at 700x to 1000x, or 75% chlorothalonil at 600x to 800x and other fungicides once every 10 days, for 5 to 6 consecutive sprays, alternating the several chemicals, with remarkable control efficacy.
Fusarium wilt
Fusarium wilt is a devastating disease for golden privet. Once it occurs, almost all plants die, so prevention work is the key.
After golden privet becomes infected, the leaves wilt and droop, lose their luster, gradually lose their green color and turn yellow and withered, until the entire plant dies, while underground the fibrous roots die.
Golden privet Fusarium wilt is a fungal systemic infection disease. The pathogen overwinters in the soil and in diseased plant residues, invades through the underground roots, spreads to all parts of the plant through the vascular bundles, and multiplies within the vascular bundles, causing blockage or poisoning, which causes the plant to wilt and eventually die. After the pathogen infects the roots, the transport functions for nutrients and water are lost, so the plant suffers nutrient deficiency and then dies. High temperature and high humidity favor the occurrence of the disease, so the peak period of golden privet Fusarium wilt is from June to August each year and continues until October.
Prevention and control methods: This disease should be prevented first, with prevention more important than cure. Strengthen cultivation management, enhance plant resistance and reduce the chance of disease occurrence. In mid-to-late May, spray fungicides preventively on key diseased areas, using protective fungicides such as zineb and mancozeb. At the same time, drench with 50% carbendazim wettable powder at 500x to 600x, or 75% thiophanate-methyl at 600x to 700x, or 75% chlorothalonil at 600x to 800x and other fungicides, drenching once every 10 to 15 days for 6 to 7 consecutive drenchings, alternating the several chemicals, with relatively good control efficacy.