ORGANIC CONTROL OF VINE WEEVILS |The Garden of Eaden

Organic control of vine weevils

As garden pests go, the hatred that gardeners have for vine weevils is right up there along with slugs and aphids. But it’s not just the amount damage they cause that is the problem, it is the sneaky way they go about it. The adult vine weevil, in between making a significant number of unsightly, irregular notches in the sides of your plants leaves, will lay their eggs in the soil at the base of their preferred plants so that the larvae can munch their way through the root system completely unnoticed until your plant topples over in a unrecoverable heap.

Unfortunately, not only is this often the first symptom you'll come across, it is usually far too late to do anything about it.

Although there are a number of effective chemical treatments available, they are all non-specific, able to kill off beneficial pollinating insects such as lacewings, bumble and honey bees just as easily as the vine weevil.

BIOLOGICAL CONTROL

Adult vine weevil

This can be a very effective method of control on infected pot grown stock where both the roots and the larvae are localized. Parasitic nematodes, which occur in minute numbers naturally in the soil, are watered into the growing medium in very large numbers.

Surprisingly it is not the nematodes that kills the larvae directly but a particular strain of bacteria that they carry which will infect the vine weevil larvae, killing it. The nematodes then invade the body to feed on the contents and breed. The bacteria are very host specific and have no effect on mammals, reptiles, or earthworms.

HAND PICKING

For the extremely environmentally conscious gardener, you can actually go out and collect vine weevil adults yourselves although this will have to be done after dark when the adult vine weevils are active. Wait a couple of hours after sunset then, taking a torch, you should be able to see the vine weevils feeding off the leaves. Simply knock them off into a container and either kill them or – for the squeamish - release them far away from your prized plants.

Adult vine weevils hide in debris around the bases of your plants so try to keep the area immediately under them free of dead, fallen leaves and reducing the number of places that they can hide.

PHYSICAL BARRIERS

Adult vine weevil eating a hole in a leaf

Organic control of vine weevils

As the adult vine weevil will lay its eggs in the soil at the base of its preferred plants you can consider using physical barriers such as heavy duty landscape fabric to prevent the newly hatched larvae from entering the soil. This is a simple yet effective method that will deter the adults from laying eggs preventing further insect damage. You can also try sprinkling a layer of grit thickly around the plants that are already affected but you will need to act as quickly as possible for best results.

ENCOURAGING NATURAL PREDATORS

This is the best ‘Lazy Gardeners’ option as all of the hard work if done by the surrounding wildlife. We are lucky in this country as there are a number of native predators that will make short work of both adult and larval vine weevils; it is just a matter of encouraging them into your garden. The easiest way is to provide a wildlife pond and or log piles. This will attract a number of very useful mammals, amphibians and predatory insects into the garden which will feed on vine weevils, but it doesn't stop there as they will also devour other garden pests such as slugs and snails.

Below is a list of the most commonly found native animals which among other garden pests will also eat vine weevils.

The common frog

The common shrew

The common toad

Hedgehogs and ground beetles