Vine weevil on rhododendron and azalea
Rhododendron and azalea are the host everyone recognises. Adults chew half-moon notches in the leaf edges at night, and that damage is cosmetic. The grubs in the soil are what kill the plant: they strip fine roots in autumn and larger roots in spring, and can girdle the stem below the soil line. UMass reports that nematodes work well against spring larvae in container stock, but results in the landscape have been varied. Water the soil first and keep it moist for several days after application.
At a glance
- Damage
- Notched leaf edges above, C-shaped grubs eating the roots below
- Type
- Root
- Settings
- Garden, Indoors, Under glass
- Threshold
- Half-moon notches on the leaf edges show adults are present
- Release
- Heterorhabditis bacteriophora
- Rate
- 250k–500k /m² of soil under the canopy; water the ground first and keep it moist afterwards
How to confirm it
Tip a wilting plant out of its pot. Vine weevil grubs are plump, white, legless and C-shaped with a light brown head, about 3/8–5/8 inch (10–15 mm) long when full grown, curled among the roots. Adults are dull black snout beetles 3/8–1/2 inch (9–13 mm) long that cannot fly and cut half-moon notches in leaf edges at night.
Identification, lifecycle, degree days and every control option are on the full Black vine weevil profile. Not sure it is this pest? Answer four questions about the damage.
Work it out
How many do I need?
Carries Heterorhabditis bacteriophora and azalea & rhododendron through so nothing is re-entered. Open the calculator →