A Detailed Guide to the Prevention and Control of Pests and Diseases of Rhododendron delavayi

I. Leaf Gall Disease

Leaf gall disease is one of the common diseases of rhododendron flowers, also known as blister disease. Leaf gall disease mainly attacks the young leaves and flower buds of Rhododendron delavayi, including all new tender tissues. The symptoms of leaf gall disease are translucent yellow round patches on the upper surface of the leaves, while the underside of the leaves is pale red and accompanied by enlarged, thickened leaves. After the flower buds are attacked, they also become abnormally thick and fleshy, and in severe cases this disease causes the affected parts to dry up and drop off. The prevention and control method is also very simple: before leaf gall disease occurs, you can spray Bordeaux mixture at a concentration of 1:1:200; if leaves with leaf gall disease are found, they need to be removed. Before sprouting, Bordeaux mixture at 1:1:200 also needs to be sprayed 2-3 times, generally once every seven to ten days; if leaf gall disease has already been found, then 65-80% mancozeb 500-fold solution or 0.3-0.5 degrees Baume lime sulfur mixture needs to be sprayed 3-4 times, generally also once every seven to ten days.

II. Leaf Spot Disease

Leaf spot disease has another name, brown spot disease. As the name suggests, its symptom is that it turns the leaves red-brown, and in severe cases they turn dark brown. The prevention and control method for leaf spot disease is to spray 70% thiophanate-methyl 1000-fold solution, 20% triadimefon 4000-fold solution, and 50% mancozeb 500-fold solution between May and August each year, generally once every ten days, for a total of seven to eight sprays. Only in this way can the development of the disease be checked.

III. Coin Blight Disease

Coin blight disease is a disease caused by aphids biting and infecting the leaves, so the most important thing is to kill the aphids. The symptom of coin blight disease is that the leaves become covered with a mite-like layer, and in severe cases it causes the leaves to dry up, affecting the ornamental value of Rhododendron delavayi. The method to prevent and control this disease is to promptly remove the diseased leaves and promptly spray a medicinal solution containing copper sulfate to kill the aphids.

The pests and diseases of Rhododendron delavayi are actually very easy to prevent and control; the most important thing is to always pay attention to the growth state of the flowers, identify the disease, treat it with the right remedy, and remove it promptly.