Disease and Pest Control of Rhododendron dew

one. Brown spot disease:

The disease affects the leaves, causing them to develop dark brown spots, affecting the growth and ornamental value of the Dewdrop Azalea tree. It often occurs from May to August when the temperature is high and the humidity is high. To prevent it, timely shade and moisture-proofing are required, and water accumulation in the cultivation soil should be prevented to cause root rot of the plant. >

If the leaves have already started to become diseased, they must be removed in time. Second, spray pesticides must be prepared, including mancozeb (50 percent concentration, 500 times diluted), thiophanate-methyl (70 percent concentration, 1,000 times diluted) and triadimefon (20 percent concentration, 4,000 times diluted). Spray once every ten days, for a total of seven to eight times.

two. Leaf swelling:

The disease is caused by fungi and affects young buds, new leaves and new shoots. Once infected, they will not only become swollen, thick and hypertrophic, but also have a grayish-white powdery layer attached to the surface.

Leaf swelling is most common at the turn of spring and summer, followed by late summer and early winter, especially in rainy and humid weather.

For prevention purposes, special fungicides should be sprayed before buds emerge; Bordeaux mixture (1:1:200) should be sprayed when new shoots and leaves are about to emerge, and diseased leaves should be removed in time. After confirming that it is leaf swelling disease, spray mancozeb (about 70% concentration, 500 times liquid) or lime sulfur mixture (0.3-0.5 degrees Baume) three to five times.

three. Coin plague:

This disease is caused when leaves are infected by aphids, usually affecting the front end of the leaves.

At this time, spray the plant with copper sulfate solution and be sure to remove the diseased leaves.

Four. Crowned web bug:

The crown web bug is a pest that sucks dew from the leaves of azalea, causing pale spots on the front and rust-like yellow on the back, leaving the entire leaf completely devoid of green, eventually causing the leaves to fall and the flowers to fail to germinate.

This disease is generally prevented and controlled in winter. First, use white paint to brush the tree trunks. Second, spray special medicine once every ten days or half a month, for a total of two or three times. Third, strengthen cleanliness and clean up the surrounding weeds and fallen leaves in time.

5. Red spider:

Spider mites are similar to crowned webbing bugs and can suck dew from azalea leaves, leaving them with pale spots and causing the leaves to drop.

This disease often occurs during the high temperatures in summer. The insect pests are reduced during rainy seasons and worsen during the dry season. Cleaning up the surrounding weeds and fallen leaves in winter can have a preventive effect, and then use insecticide to kill insects after pests appear.