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).

Capnodis tenebrionis is one of the most important pests in cultivated stone fruit (f.e. cherries, apricots and almonds) and in some cases seed fruit (apples and pears). The beetle has been a serious threat in the Mediterranean area and Middle-East for several decades.

 

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.

• Adults of Capnodis tenebrionus feed on twigs and young branches mainly causing problems in tree nurseries and young plants. The greatest damage is caused by the larvae. They penetrate into the roots of the trees and feed on the cortex. Young trees die as a result of this damage. A few larvae can also cause the death of an adult tree in 1 or 2 years.