How to Prevent and Control Sunflower Brown Spot? A Detailed Guide to the Latest Methods
Brown spot is one of the diseases that commonly occur in sunflowers, one of the main diseases causing yield loss and empty seeds in sunflowers, and one of the main reasons affecting their yield. So how should sunflowers be protected against brown spot? Let's take a look together.
1. Symptoms
When seedlings are affected, nearly round lesions form on the cotyledons or young leaves. The front of the lesion is brown with a yellow halo around it, while the back is grayish white. When plants are affected at the adult stage, irregular or polygonal brown lesions form on the leaves, surrounded by yellow halos, with the center of the lesion gray and scattered with small black dots, namely the pathogen's conidia. In severe cases, the lesions merge into patches, the leaves wither and die, and the petioles and stems can also be infected, showing narrow brown streaks. Its symptoms are somewhat similar to leaf spot, but the lesions of brown spot are larger and have concentric rings. When the weather is humid, brown mold-like growth appears on the lesions.
2. Occurrence Pattern
Brown spot overwinters as pycnidia or mycelium on diseased plant debris. When temperatures are suitable in spring and summer, especially during continuous rainy days, the pathogen multiplies in large numbers and releases a great many conidia, which spread by wind and rain. Generally, the disease is more severe in continuous cropping fields and low-lying fields, in plots with severe disease the previous year, and when field humidity is relatively high.
3. Agricultural Control
Crop rotation is the best way to prevent this disease. Rotating with grass family crops for more than 3 years can greatly reduce the likelihood of this disease occurring. Before planting, thoroughly remove diseased and residual leaves and deeply plow the soil to reduce sources of inoculum. At the same time, select varieties with strong disease resistance according to local conditions, plant at a reasonable density, and apply sufficient well-rotted organic fertilizer to strengthen the plants' disease resistance. Strengthen field management, drain promptly after rain to reduce field humidity, and irrigate reasonably; flood irrigation should be avoided.
4. Chemical Control
When the disease occurs, promptly remove diseased leaves and spray chemicals for control at the same time. Brown spot is a fungal disease, and many fungicides have good effects against it. For example, carbendazim, thiophanate-methyl, basic copper sulfate, basic copper sulfate and other chemicals. Generally, spray once every 10 days, and 1-2 consecutive treatments are sufficient.
The above is an introduction to the prevention and control methods for sunflower brown spot. We hope it can help you. To learn more related knowledge, please stay tuned to us.