Causes of Leaf Drop in Golden Privet During the Growing Season and Solutions

Golden privet (Ligustrum × vicaryi) is an excellent colorful shrub. In practical cultivation in some places, during the growing season its leaves, especially new leaves, successively develop spots, which then progress to drying up, leaf drop, and the branches gradually die back from top to bottom, with a small portion dying. According to surveys, the deaths mostly occur in the middle of the planting plots, while the plants around the edges grow well. The causes are mainly the following two aspects.

1. Caused by disease

The cause of this condition is golden privet leaf spot disease. Leaf spot disease 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 lesions sometimes merge together, and eventually the leaves scorch and drop off.

2. Damage by scale insects

Scale insects are relatively small, about 2 mm, and crawl quickly on the branches before settling. Where branches and leaves are too dense and ventilation and light penetration are poor, the pest damage is severe, often causing leaf drop and even causing the plants to wither and die.

Control measures

1. The planting site should be conducive to drainage, and waterlogging must not occur. Plant at a reasonable density, and as the plants grow, thin out the branches appropriately to enhance ventilation and light penetration inside the plants and reduce humidity.

2. Reduce sources of disease infection. Remove diseased and residual plant material from the planting site, and remove weeds at any time.

3. Strengthen fertilizer and water management. In road landscaping, the soil is generally rather poor, and combined with little fertilization, this easily leads to nutrient deficiency in the plants. Applying fertilizer once in spring and broadcasting compound fertilizer during the rainy season in conjunction with rainfall are both beneficial for improving the disease resistance of golden privet and promoting early recovery after disease.

4. Prune at the appropriate time and treat wounds promptly. Heavy pruning can be done in winter, but pruning should be reduced once the rainy season begins, to reduce wounds and lower the chance of pathogens invading through wounds. Spray fungicide immediately after pruning. Many years of practice have proven that the more frequently pruning is done during the rainy season, the more severe the disease.

5. Spray chemicals regularly for control. Starting in late June, spray once every 7-10 days until the rainy season ends in September. In the early stage of the disease, systemic fungicides can be used, such as carbendazim, thiophanate-methyl, and Likojun. In the later stage, protective fungicides can be used, such as Bordeaux mixture and mancozeb. To prevent the pathogens from developing resistance, the chemicals can be used alternately. To control scale insects, imidacloprid can be used together with fungicides before the insects have settled.