Furrowed vine weevil
| Furrowed vine weevil | ||||||||||||
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Furrowed vine weevil ( Otiorhynchus sulcatus ) |
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Otiorhynchus sulcatus | ||||||||||||
| ( Fabricius , 1775) |
The furrowed black weevil ( Otiorhynchus sulcatus ), also known as the white weevil , is a beetle from the family of the weevils (Curculionidae). The adult animals ( Imagines ) feed polyphagous , mainly on leaves, buds or young plants instincts of agricultural crops and ornamental plants, while the larvae feed on roots. Preferred plant genera and species are, for example, strawberries , rhododendrons , cherry laurel , eu cone and yew .
features
The beetle grows to around ten millimeters. The top of its body is colored black and has dark brown spots. It can be grainy or wrinkled. The upper wings (elytres) are hardened like armor, elliptical and strongly rounded at the shoulders. The thigh is strongly thickened in the middle. The trunk is provided with strongly developed pterygias (shell- or ear-shaped bulges on the outside next to the antennae pits).
The larvae are about the same size as the beetles. They are yellowish-white in color with a brown head capsule. The larvae are legless and curved belly. The adult animals are crepuscular or nocturnal and live on herbaceous plants or smaller woods. There they appear from April to October. Although adult beetles are unable to fly, they can cover relatively long distances on foot.
Occurrence and distribution
The genus Otiorhynchus is native to Europe. The furrowed black weevil is endemic to regions with a temperate climate . It was transported to various other regions of the world via the import of plant material and spread to various plant species. Today it is a major pest in the United States, Canada, Japan, New Zealand, Southeast Australia and Tasmania.
The adult animals are crepuscular or nocturnal and live on herbaceous plants or smaller woods. There they appear from April to October. The pest is often introduced with the substrate or via potted plants, from which they then spread to the various plant species.
Reproduction and development
Often there is a virgin generation ( parthenogenesis ) among the animals , so that they are not dependent on sexual reproduction. The offspring are all female. The laying of eggs - 500 to 1000 eggs per female - takes place individually from around June or in piles at the bottom of the feeding plants or in humus soil. The initially white, but soon brownish, approximately spherical eggs with a diameter of approx. 0.7 mm initially have a liquid, clear, later whitish content. After two to three weeks, the larvae hatch and feed on the roots. The last larval stage digs a small cave in the ground for pupation. The young beetles hatch around the end of May / beginning of June and are sexually mature after four to five weeks. They overwinter mostly as a larva, less often as a pupa or as an adult beetle. One generation develops per year under natural conditions, whereby the larvae appear preferentially in spring (overwintered "old larvae" from the previous year) and in autumn (young larvae from oviposition in summer). New generations of beetles develop over and over again via the egg, larva and pupa.
Damage
The larvae cause the main damage through their feeding activity in the root area: Woods show stunted growth, while herbaceous plants show signs of wilting. If the larvae are heavily infested, the plants can even die. The adult beetles, on the other hand, eat semicircular indentations in the leaf margins (pests); the leaf margin appears notched like a gear. Damage to buds or shoots caused by gnawing off the bark can also be observed. The furrowed black weevil can cause great damage in viticulture , tree nurseries, strawberry plants and ornamental plants.
Combat
Adult beetles can be controlled with insecticides . Collecting the adult animals can only serve to determine the infestation pressure and does not constitute a control. Entomophage nematodes of the genus Heterorhabditis can be used against the larvae which cause much more severe damage . These penetrate through the skin or body orifices into the beetle larvae and give symbiotically with nematodes living bacteria of the species Photorhabdus luminescens to the insect blood from. This bacterium multiplies rapidly and leads to the death of the beetle larva within a few days. Infected larvae turn reddish or brownish in color. The nematodes themselves feed on the bacteria, multiply, then swarm out of the dead larva and look for new larvae. To control black weevil larvae with nematodes, the soil temperature must be at least 10 ° C. In addition, the soil must be moist for approx. 10 days after the treatment so that the nematodes can move freely. The nematodes also act against the pupae of the black weevil.
Individual evidence
- ^ R. van Tol, 2002: Fatal Attraction. Novel Strategies for Vine Weevil control. Academic proof. ISBN 90 76894 21 3 .
- ↑ Rebstichler - Dickmaulrüssler, Merkblatt 021, Agroscope Changins-Wädenswil ACW ( page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.
literature
- M. Fortmann, 1993: The great cosmos book of beneficial insects. New ways of biological pest control. Franckh-Kosmos publishing house.
Web links
- Fauna Europaea: Taxonomy (English)