1、 Brown spot:

The disease acts on the leaves, making them grow dark brown spots, affecting the growth and ornamental of dew Rhododendron. It often occurs from May to August when the temperature is high and the humidity is high. It is necessary to timely shade and prevent humidity, and prevent ponding in the planting soil from causing plant rhizome rot& gt;

If there are already leaves with lesions, first, they should be removed in time, and second, they should be sprayed with mancozeb (50% concentration, 500 times solution), methyltobutrazine (70% concentration, 1000 times solution) and Triadimefon (20% concentration, 4000 times solution). It takes seven to eight times every ten days

2、 Leaf swelling:

The disease originates from fungi and acts on buds, new leaves and shoots. After infection, it will not only make them swollen, thick and hypertrophic, but also have a gray white powder layer attached to the surface

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

In order to prevent, it is generally necessary to spray special fungicides before budding; When the new and slightly new leaves will come out, spray Bordeaux liquid (1:1:200) and remove the diseased leaves in time. After confirmed as leaf swelling, spray mancozeb (about 70% concentration, 500 times solution) or stone sulfur mixture (0.3-0.5 Baume degree) three to five times

3、 Coin disease:

The disease can be caused after the leaf is stabbed and infected by aphids, which generally acts on the front of the leaf

At this time, the potion added with copper sulfate should be sprayed, and the diseased leaves should be removed at the same time

4、 Crown net bug:

The crown net bug is a kind of pest. It pricks and sucks the leaves of the dewdrop Rhododendron to produce pale spots on the front and rust like yellow on the back, but the whole leaf has no green, which eventually leads to the falling of the leaves and the inability of the flowers to germinate

The disease is generally prevented and treated in winter. First, we should use white paint to brush the trunk; Second, spray special potions once every ten days and a half months, a total of two or three times; Third, we should strengthen the cleanliness and timely clean up the surrounding weeds and fallen leaves

V Starscream:

Red spider is similar to the crown web bug. It stabs and sucks the leaves of dew azalea to make them have pale spots, causing the leaves to fall

The disease mostly occurs in high temperature in summer, the pest is reduced in cloudy and rainy seasons, and the pest is aggravated in dry seasons. In winter, clearing the surrounding weeds and fallen leaves can play a preventive effect. When pests occur, use mirex to kill insects