Rhododendrons are highly susceptible to the Black Vine Weevil. The Root Weevil is the larvae version of this insect. The adults resemble a small black beetle with a distinctive long nose, and feed mostly at night. When they feed, they cause characteristic notches around the edges of the leaves and flowers.
Black Vine Weevils are very difficult to control and can repopulate very quickly. Unfortunately, there is no magic cure for this problem. The most we can hope for is to carry out treatments that will prevent their population from getting out of hand. The most effective control is to target the larvae of the Black Vine Weevil (Root Weevil).
The recommended treatment is with Nematodes (microscopic worms) which aggressively seek out the Root Weevil. They enter the grubs through natural body openings, and once inside, they release bacteria which will kill the insect quickly. These nematodes are non-toxic, occur naturally in the soil, and are completely safe to the environment. The time of application is critical for the Nematodes to work so we recommend 2 treatments, the first in the fall and the second in the spring.