Beetles

Introduction

There are some beetles which cause damage in the horticulture, arable farming and public green spaces. An important pest species in the ornamentals is the black vine weevil, Otiorhynchus sulcatus, while the garden chafer, Phyllopertha horticola, causes a lot of damage in the grassland. Asparagus growers face the problem of the common asparagus beetle (Crioceris asparagi).

Biology

Beetles go through four life stages, namely egg, larva, pupa and adult. Larvae has biting mandibles and mostly feed themselves with the same food as the adults. Some larvae are legless and look like caterpillars.

Damage symptoms

• Vine weevils are only active at night. They take semi circular bites from the edges of the leaves. This notching decreases the ornamental value of the plant. Larvae sometimes damage shrubs and young trees by feeding on buds and soft bark.
• Larvae cause most damage. Smaller larvae feed mainly on root hairs, but the larger larvae feed on roots and the stem base. That hinders growth and eventually causes the plant to turn yellow and wither. One larva is enough to kill a plant, if it girdles the base of the plant stem.
• Larvae of the rose beetle Phyllopertha horticola cause severe damage to lawns by eating the roothairs of the grass. This reduces the uptake of water and nutrients. Moreover, animals like birds, fox, swine and hedgehogs searching for grubs, damage the lawn seriously.
• The larvae of the common asparagus beetle eat the parts of the asparagus plant that are above ground. The larvae climb down the plant to pupate in the soil. The adults eat only asparagus foliage.