Key Pest and Disease Control Methods and Techniques for Chestnut
1. Select good varieties and prepare enough scion wood. Select good varieties. For the improvement of chestnut orchards, the three new varieties Dahongpao, Qingmaozao and Hongmaozao should be selected. These new varieties have been trial-planted in our city and have the characteristics of early fruiting, high quality, high yield, large fruit and strong stress resistance, and are suitable for promotion and planting throughout the city. Scion collection and storage...
1. Young shoots After the young shoots become diseased, brown lesions about 2 mm in diameter appear on the hypocotyl, followed by small dark brown spots 1 mm in diameter on the cotyledons.2. Leaves When leaves are infected, small grayish brown or dark brown raised spots first appear, which then expand into dark brown circular lesions 2-6 mm in diameter, with obvious concentric rings and a yellow-white halo around the edge. When the air is humid, black mold-like growth appears on the lesions, which can cause the leaves to wither and die.
3. Stems, petioles, stems and fruit stalks When infected, the lesions are oval to spindle-shaped, dark brown with concentric rings; when they encircle the lateral branches and main stem, they cause the lateral branches or the entire plant to wither and die.
4. Pods The lesions on pods are basically similar to those on leaves. In severe cases, the seeds stop growing and form red seeds, and the pods tend to split before harvest; when humidity is high, mycelium can grow inside the pods.
Infection cycle
The pathogen overwinters or oversummers as mycelium or spores in diseased plant residues and inside and on seeds. In the south, the disease can occur year-round, causing damage in successive cycles, with no obvious overwintering period. After oversummering and overwintering, the mycelium forms conidia under high humidity conditions, which spread with the wind and cause primary infection. Sowing infected seeds can cause seed rot and seedling death. New conidia produced on diseased plants can spread with the wind and cause multiple secondary infections.
Occurrence characteristics
Brassica rapa (Chinese cabbage type) is the most susceptible, while Brassica napus (cabbage type) is relatively resistant. High temperature and high humidity favor the disease. If high temperature and rainy weather occur during the flowering period of rapeseed, the incubation period is short and the disease develops easily. Rainy weather during pod development is extremely favorable for spore spread and infection. In low-lying fields with continuous cropping and with excessive single application of nitrogen fertilizer, the disease is severe.
Control methods
1. Agricultural control Select disease-resistant varieties or disease-free seeds, and retain seeds from disease-free plants before harvest. Rotate with non-cruciferous crops. Avoid excessive single application of nitrogen fertilizer and pay attention to increasing potassium fertilizer. Water at the proper time and in the proper amount. Clean up diseased plant residues in the field in a timely manner.
2. Seed treatment Soak seeds in warm water at 50°C for 20-30 minutes. Seeds can also be dressed with 0.4% of seed weight of 50% thiram or 0.25% of 50% iprodione, or soaked in 100-fold 40% formalin solution for 25 minutes, then washed clean, air-dried and sown.
3. Field spraying Spray promptly for control at the early stage of disease in the field, once every 7 days, and spray 2-3 times consecutively depending on disease severity. Fungicides can be selected from 1500-fold 50% iprodione solution, or 600-fold 75% chlorothalonil solution, or 500-fold 64% oxadixyl-mancozeb solution, or 800-fold 80% penconazole solution, or 600-fold 12% copper green emulsion oil, or 500-fold 70% mancozeb solution.