Common diseases and insect pests of rhododendron and their control

Rhododendron is mainly for ornamental use, and has strong vitality and is easy to plant. Cuckoos have four love and five fear habits, that is, love semi-shade, love cool, love moist, love acid soil; afraid of hot sun, afraid of heat, afraid of thick fat, afraid of soot, afraid of sulking. This paper introduces the common diseases and insect pests and their control methods.

(1) rhododendron disease. In the process of cuckoo growth, the diseases on the leaves can be divided into two types: physiological diseases and pathological diseases.

(1) physiological diseases. In the process of cuckoo growth, iron deficiency chlorosis often occurs if there is a lack of trace element iron. In the early stage of the disease, the new mesophyll becomes chlorotic and yellow, and the leaf vein is still green, thus forming green reticulate leaves. With the aggravation of the disease, the whole leaf is yellow and white, leaf tip, leaf edge scorched, and finally lead to leaf fall. To prevent and cure rhododendron chlorosis, regular supplement of iron can be adopted, that is, 0.2%-0.3% ferrous sulfate is sprayed on the leaves at the initial stage of the disease, slightly mixed with adhesive, once every 25 days, and the effect is quite good.

(2) pathological diseases. Due to the invasion of germs, cuckoo leaves often suffer from diseases such as brown spot, coal fouling, gray mold and so on. In practice, it is found that the incidence probability of brown spot and coal fouling disease is higher, accounting for more than 75% of pathological diseases, and the closer to the urban area, the higher the proportion.

Brown spot: the disease spot on the leaf is reddish brown, brown, and gradually becomes yellowish white or grayish white in the later stage, with a dark brown leaf margin. The shape of the disease spot is often round and polygonal, and there are gray-black mildew spots on the surface when it is wet. The control method is to strengthen cultivation management, cut off diseased leaves, and timely spray 50% methyl topiramate wettable powder 800 times, once every 15 days, until the end of August.

Coal fouling disease: there is a layer of coal ash on the leaves, when it is serious, the whole plant is polluted, the branches and leaves wither, and the plant dies. In control, it is necessary to eliminate vector pests, scale, aphid, etc., and maintain ventilation and light transmission, and spray with 1000 times of carbendazim wettable powder, the effect is better.

(2) Rhododendron pest. The most common pests of cuckoos are red spiders and military insects.

The main results are as follows: (1) the damage of red spiders: in the high temperature season from June to August, the damage of red spiders is serious and often makes the leaves of rhododendron turn yellow and fall off. The control method can be sprayed with triclofenac 1000, once a week for 4 consecutive times.

(2) damage caused by military insects: rhododendron is often damaged by military insects from May to July every year, and spreads more rapidly when the climate is dry. The commonly used control method is to spray with 1Comp1500 dimethoate or dichlorvos.