What are the methods for controlling rhododendron pests?
1. Red spider mites
Red spider mites on rhododendrons mainly occur on the underside of the leaves, and when the infestation is relatively large, they are also distributed on the underside of the leaves and the young shoots. After red spider mites appear, the leaves develop fine, scattered spots of alternating yellow and green.
Control methods: Create a well-ventilated environment so that the rhododendron grows vigorously and its resistance to red spider mites increases. If the infestation is relatively large, the heavily infested areas can be cut off to reduce their population; if the infestation is dense on many branches, insecticides of the nicotine-based bio-source type such as abamectin can be sprayed.
2. Rhododendron lace bugs
Rhododendron lace bugs mainly occur on the underside of the leaves. When they appear, some black spots and small insects about 2-3 mm long with transparent wings can be seen on the underside of the leaves, and spots of alternating yellow and green also appear on the upper side of the leaves, but they are finer than the spots that appear with red spider mites. When they occur, they spread from the leaf veins toward the leaf margins, and the infestation in the center of the leaf is noticeably greater than at the margins.
Control methods: If there are relatively few pests, the diseased leaves can be picked off and burned to prevent re-infection; if the infestation is relatively large, imidacloprid can be used for control.
3. Aphids
Aphids mainly occur on the underside of the leaves and on the young shoots, where some small greenish-white insects appear, some winged and some wingless, usually clustered together.
Control methods: When the infestation is small, they can be taken to a faucet and washed off; or some yellow sticky traps can be hung around the rhododendron; soaking tobacco in water can also be used for control. If the infestation is relatively large, imidacloprid can be sprayed. After one application, a second application should be made 3-7 days later to kill the larvae that have not hatched from the eggs.