Weevils are one of the most common and destructive rhododendron pests. The insects eat the leaves of the plant, weakening it and eventually killing it. Weevils live in leaf litter on the ground and climb rhododendrons at night to feed. This feeding pattern makes controlling weevils easy, though it does require spending some time outdoors at night.
Fill a bucket with water and two squirts of liquid dish soap. Agitate the water with your hands to create suds. Take the bucket outside to your rhododendrons.
Wait until nightfall, then lay a white towel or sheet under the base of the plant, wrapping the trunk. Gently shake the rhododendron. Watch as the weevils fall off the plant and onto your towel. Weevils, which are grey or blackish brown in colour, are about 1/4- to 1/2-inch long and have a short broad snout with antennae attached. When you stop seeing weevils fall, quickly submerge the towel in the soapy water and leave it underwater to drown the bugs.
Use a flashlight to thoroughly examine the plant after you remove most of the weevils by shaking. Pick off any remaining weevils you see and dunk them in the soapy water.
Wrap the base of the rhododendron in clear cling film. Coat the plastic in a layer of sticky insect barrier. The sticky barrier traps the weevils as they try to climb up the trunk of the shrub. Remove the cling film once every three days and replace it with new sticky barrier.
Pour a 1-inch layer of coffee grounds around the base of the shrub. The grounds act as a natural repellent.
Clear any dead leaves or mulch from the base of the plant. Weevils live in loose litter near the trees, and removing their living environment prevents them from breeding near your plants.
Use garden shears to remove any branches that touch the ground.