What to Do About Golden Privet Leaf Drop During the Growing Season? Causes and Control Methods

Causes and Control Measures for Leaf Drop of Golden Privet During the Growing Season

Caused by Disease According to expert research, this leaf spot disease is caused by the pathogenic fungus Alternaria (afternaria) of the order Moniliales, class Hyphomycetes, subdivision Deuteromycotina. In the early stage, small brown spots appear on the leaves, surrounded by purplish-red halos, and black mold-like growth is visible on the spots, namely the pathogen's conidiophores and conidia. As temperatures rise, several spots sometimes merge, and eventually the leaves wither and drop off. Alternaria fungi mainly overwinter as mycelium on diseased plant debris on the soil surface. Conidia spread through airflow or contact between branches and leaves, and invade the host through wounds, stomata, or directly. The incubation period is 10 to 20 days. The optimum temperature for pathogen growth is 26°C, and the optimum temperature for spore germination is 18°C to 27°C. Under suitable temperature and high humidity, spores can germinate within a few hours. Last year, the Hengshui area entered the rainy season early in June, and it lasted until September. Because the plants were planted densely and ventilation and light penetration were poor, a relatively stable environment of high humidity and suitable temperature formed among the plants, which was very favorable for spore germination and invasion, causing a major outbreak of the disease.

Scale insect damage Scale insects are relatively small, about 2 mm, and crawl quickly on branches before becoming fixed. Where branches and leaves are too dense and ventilation and light penetration are poor, pest damage is severe. It often causes leaf drop, and in severe cases can also cause plants to wither and die.
To prevent and control leaf drop of golden privet during the growing season, the following control measures can be taken, with good results.
1. Choose a good site and get planting right. Keep the planting site on relatively high ground; it must never accumulate water. Plant at a reasonable density, and as the plants grow, thin out branches reasonably to enhance internal ventilation and light penetration and reduce humidity.
2. Strengthen cultivation management and apply more organic fertilizer. Use nitrogen and phosphorus fertilizers together so that the seedlings grow vigorously and their stress resistance is enhanced. Avoid over-applying quick-acting nitrogen, which causes leggy growth of the seedlings.
3. Clean up the planting site and block the source of the pathogen. After each pruning, promptly remove the cut leaves and branches from the planting site, remove weeds at any time, and always keep the planting site clean and free of debris. Reduce overwintering mycelium and block the source of the pathogen.
4. Prune at the right time and treat wounds promptly. Once the rainy season begins, prune little or not at all to reduce wounds and lower the possibility of pathogen invasion. No matter when you prune, spray a fungicide immediately after pruning for protection.
5. Spray regularly for prevention and control. Disease control must focus on prevention, combining prevention with control. Starting in late June, spray a fungicide every 7 to 10 days, and spray an additional fungicide after each rain, until the rainy season ends in September. In the early stage of the disease, systemic fungicides such as carbendazim, thiophanate-methyl, and Liketjun can be used. To control scale insects, imidacloprid can be used together with fungicides before the insects become fixed. In the later stage, protective fungicides such as Bordeaux mixture and mancozeb can be used. To prevent the pathogen from developing resistance, systemic fungicides and protective fungicides can be used alternately.

Causes and Control Measures for Leaf Drop of Golden Privet During the Growing Season