Rhododendron is a beautiful flower, but it may encounter some pests and diseases during the maintenance process. Here are some common rhododendron pests and diseases and how to control them:
1.*Disease**:
Brown spot disease**: Caused by cercospora fungus, it appears as a reddish-brown dot on the leaves that gradually expands into near-round or polygonal lesions. Control methods include clearing fallen leaves, maintaining ventilation and light, and spraying with polysulfide suspension or carbendazim wettable powder.
Leaf blight**: Caused by Polychaete disc, it mainly occurs in old leaves, forming irregular leaf margins and dry leaf tips. The control method is to remove fallen leaves and spray with mancozeb wettable powder or propiconazole emulsifiable concentrate.
Leaf swelling disease**: caused by ectobacterium, mainly harms young leaves and young shoots. Control methods include winter and spring cold protection, and spraying with carbendazim wettable powder or zebzeb wettable powder.
Lobular disease**: caused by zinc deficiency, manifested by significantly smaller leaves and hard and brittle leaves. The control method is to improve the soil so that the soil pH is less than 6, and apply zinc sulfate at the onset of the disease.
Yellowing**: Caused by iron deficiency, it is characterized by the initial greening of the leaves and the complete yellowing of the whole leaves. Control methods include soil improvement, spraying with ferrous sulfate solution or root irrigation.
2.*Pests**:
Red spider**: small in size, serious damage to rhododendrons. Control methods include manual killing and spraying with stone sulfur mixture.
Matchworm**: Adults are small and flattened, mainly sucking leaf sap on the back of leaves. Control methods include spraying with trichlorfon, dimethoate EC or pine borer emulsion.
Aphids**: Mainly damage young branches and leaves, causing them to lose their green color or curl up. Control methods include spraying stone sulfur mixture during the overwintering period to eliminate overwintering eggs, and spraying dimethoate or oxydimethoate during the aphid-infested period.
Brachybeard moth**: often sucks sap near the main vein on the dorsal side of the leaf. Control methods include spraying stone sulfur mixture and insecticidal aqueous agent in mid-to-late October and early spring in March.
The above information is ** in the encyclopedia. It is recommended to read carefully and follow the product instructions when controlling pests and diseases to ensure safety and effectiveness.