What are Vine Weevil?
Vine weevil cause damage to bonsai trees and accent plants in two main ways; the adult weevil will eat leaves during spring and summer, while the larvae feed upon roots over autumn and winter.
The larvae do the most damage, they can go undetected in the soil and can ultimately kill the bonsai.
Vine weevil tend to prefer potted plants putting bonsai at special risk, rarely infesting ground growing trees.
What Trees do they infest?
The adult vine weevil will target the foliage of most herbaceous plants and shrubs, particularly Azalea and evergreens such as Euonymus.
The larvae stage will feed upon soft roots of most trees, especially Yew and plants such as sedum, sempervivum and strawberries.
Other species of weevil will target trees such as privet but like vine weevil the larvae do far more damage.
How to Spot them
- In spring and summer you may notice irregular-shaped notches cut out of leaf margins
- Adult vine weevils are approximately 9mm long and dull black colour
- A bonsai with vine weevil larvae infestation in the soil will wilt and possibly die during spring.
- The larvae grow to approximately 10mm long, tend to be ‘C’ shaped, white in colour with a light brown head.
Non Pesticide Control
- Vine weevil prefer a soft, damp soil for larvae habitat and use of inorganic soils are the best deterrent
- You can go out during a spring or summer evening and pick off the adult weevils by torchlight, also look under pots
- You can use insect glue traps placed around pots or benches to trap adult weevils
- Biological pest control is available for vine weevil, these include Steinernema Kraussei, Heterorhabditis Megidis, Heterorhabditis Bacteriophora and Steinernema Feltiae.
- The best chemical treatment is Bug Clear Ultra Vine Weevil Killer which is a systemic pesticide containing neonicotinoid insecticide acetamiprid. This is applied to the soil as a dilute during late summer or early autumn.