Otiorhynchus sulcatus F Vine weevil

This insect is one of the most important pests of horticultural crops, both outdoors and under protection. The adults notch the edges of leaves, and often cause extensive damage in strawberry beds and in gardens and nurseries, especially on favoured plants such as camellia and rhododendron; the adults can also ring-bark young plants. The larvae are usually of even greater significance. They feed voraciously on the root system of a wide variety of cultivated plants, destroying the fine rootlets and larger roots; attacked plants often wilt and die. The larvae also burrow into crowns, corms and rhizomes. Larval damage is often severe on herbaceous plants, soft-fruit crops and containerized ornamentals.

BIOLOGY

This species is univoltine and parthenogenetic, adult females on outdoor crops usually appearing in May and June. They feed at night and rest during the daytime on host plants or hide amongst debris on the ground. Eggs are laid in the soil from late July onwards, each female depositing up to 800 or more in her lifetime. On low-growing plants, such as strawberry, eggs are sometimes placed in folds on the lower leaves.

The eggs hatch 1-2 weeks later. The first-instar larvae are very mobile and immediately migrate to the root system where they begin to feed. Individuals pass through several instars and become fully fed in the following spring. They then pupate, each in a small earthen cell. The adult stage is attained from mid-April onwards but individuals remain in situ for a period before finally emerging. Most adults die before the onset of winter but some may survive for one or more years. In heated glasshouses and other protected situations, the life-cycle is often accelerated and young adults may emerge in the autumn. Also, the period of egg laying is often protracted and, as a result, all stages of the pest may occur together.

DESCRIPTION

Adult 7-10mm long, mainly black and shiny; prothorax and elytra deeply sculptured, the latter often with several patches of yellowish hairs. Egg 0.7 mm in diameter, white and shiny when newly laid but soon becoming brownish if viable. Larva up to 10 mm long; body creamish to brownish-white; head reddish-brown (Fig. 234). Pupa 7-10 mm long, white with distinct wing pads and other appendages. NOTE Several other species of Otiorhynchus, e.g. O. clavipes (Bonsdorff), O. ovatus (L.) and O. rugosostriatus (Goeze), are associated with fruit crops; weevils from related genera (e.g. Barypeith.es and Sciaphilus) are also of pest status, e.g. on strawberry.

Fig. 234 Larva of vine weevil, Otiorhynchus sulcatus (x!5).
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