Ecogrow

Black Vine Weevil otiorhynchus sulcatus

Description | Damage | Lifecycle | Spread | Monitoring | Control | Hint

Description

Adult
Adult vine weevils are about 10 to 12mm long and are brown/black with faint yellow spots. They have the elongated snout of a weevil. This accounts for their other common name, elephant beetle. Adults are flightless and are most active at night.


Larvae
Larvae are white, curved, legless and about 10mm long when fully grown. They have orange/brown heads.

Damage

Roots
The voracious larvae feed on the root system and may be found 20 to 40mm down in the soil near the roots. Cyclamen corms may have hollows chewed into them by larvae.

Leaves
Adults produce telltale notches around the edges of leaves and flowers. They rest during the day so are seldom associated with the damage.

Stems and stalks
Adults may also chew fruit stalks of grapes. On rhododendrons and azaleas the larvae may girdle the plant by chewing bark from the lower stems.

Host Range
Ornamentals
e.g. Cyclamen, maidenhair fern, polyanthus, woody ornamentals (fuchsia, rhododendron, rose) nursery containers.
Fruit
e.g. apple, blackberry, blackcurrant, gooseberry, grape, strawberry
Nuts – walnut
Vegetables – seedlings
Weeds - various

Life cycle

Complete metamorphosis

(egg, larva, pupa, adult) with 1 generation. Adults are all female and can lay up to 1000 fertile eggs without mating. Eggs are white, round and 0.7mm in diameter. They are usually deposited in the soil or potting medium near the base of the plant.

The egg hatches into larva after 10 to 25 days. The legless larvae are whitish pink and live in the ground for about 6 months. The pupa is about 8mm long with the wing cases being free and remain in this state for approximately 20 days.

Life Cycle

Spread

Adults can walk as far as 1000 meters in a day. Larvae are often spread by plant movement of potted crops.

Monitoring

Plants
Inspect plants regularly during the spring and summer for telltale notching of the leaves. Check under the rims of pots for adults hiding during the day. In hot weather check the root system of plants that appear healthy but look stressed when subjected to slight drought stress, or continue to wilt when well irrigated.

Media
Randomly check the roots of susceptible plants for larvae from March onwards.

Trapboards
(A sheet of wood or Iron which they will use as a habitat ie to live and hide under during the day as they are active at night mostly)
Regularily lift up the trapboard to see if there are adults they will be at rest so you can physically remove them.
Note …Check for adults weekly from November to March using strategically placed trap-boards.

Pots
Check under the rims of pots for adults hiding during the day.

Damage

 

DAMAGE FROM A BLACK VINE WEEVIL

Control

Cultural
Discard badly infected plants and treat remainder.
Repot plants into fresh bark mix after the larvae have hatched.
Use susceptible varieties as indicators of infestation.
Purchase stock for resale when adults aren't active.
Purchase stock for resale from suppliers with a control program.

Chemical

Drenching larvae has proven relatively ineffective in the past due to the associated problems:
Leaching of chemicals out of the growing media alter irrigation.
Making contact with the larvae
Uniform coverage. This is difficult as the media is often protected by the foliage canopy.
Hardening of the plant cells and a reduction in growth.
Shelf life. Chemicals need to be used within a specified time or they loose efficiency.

Spraying
Spraying adults at night has proven relatively ineffective due to the fact that they drop to the ground quickly when disturbed.

Biological
Entomorpathogenic Nematodes. (EN's).
WEEVILNEM ®

They are amongst the best of biological controls.
They have no odors
They do not injure plants
They do not harm greenhouse workers

Can tolerate most commonly used pesticides used to control other pests and diseases.

Apply in the Autumn after eggs have hatched.
OR
Apply in the Spring prior to pupation and when soil temperatures have increased above 12 degrees.

Hint

Telltale signs of BVW activity Leaf notching see photo
Use trap boards as a means of detecting activity see monitoring
Check the root system of plants that suddenly deteriorate under drought or heat stress or that become flaccid.
Check under the rims of pots for adults hiding during the day.