Garden weevil in vineyards

Page last updated: Tuesday, 28 August 2018 - 12:21pm

Garden weevil (Phlyctinus callosus) was accidentally introduced into Western Australia from South Africa. This weevil is now a severe pest of grapevines and other horticultural crops. Adults feed on any soft plant tissue, and the soil-borne larvae feed on roots.

Left uncontrolled, vigour, cosmetic fruit quality, yield and growth of host crops can be adversely affected.

This article provides details on the identification, biology and management options for garden weevil in grapevines but much of the information is relevant to other crops attacked by this insect.

Description and life cycle

The garden weevil originated from South Africa where it is known as the banded fruit weevil.

Garden weevil eggs and emerging larva are pale green
Garden weevil eggs and emerging larva

Garden weevil eggs are laid in groups in loose organic matter on the soil. Eggs are small and almost impossible to find. They hatch in 10 to 14 days.

Garden weevil larvae have brown heads and are legless
Garden weevil larvae have brown heads and are legless

Larvae of garden weevil are soil-dwelling, legless and have brown heads. Young larvae immediately burrow into soil after hatching and feed on plant roots.

They are difficult to distinguish from brown-headed larvae of the apple weevil (Otiorhynchus  cribricollis), spotted vegetable weevil (Desiantha diversipes), and sitona weevil (Sitona discoideus). But they can be distinguished from white-headed weevil larvae of Fuller's rose weevil  (Asynonychus cervinus) and whitefringed weevil (Naupactus leucoloma) and leaf feeding larvae of vegetable weevil (Listroderes obliquus).

Presence of the more easily identified adult stage of weevils is a good guide to the species of larvae in vineyards. To distinguish between larvae of garden weevil and these other species, see Identifying soil beetle pests.

Larvae develop slowly during winter and more rapidly as soil temperature increases in spring. They become milky as they mature and form a smooth-sided earthen cell in which they pupate.

Garden weevil pupae are white when newly formed
Newly formed garden weevil pupae
Garden weevil pupae close to emergence as adults are darker
Advanced garden weevil pupa

Pupae are a delicate, soft-bodied stage and most abundant in September. They are white at first, and then darken. The duration of the pupal stage depends on weather conditions but it is usually completed in three to four weeks. The eyes become black and the body turns grey-brown just before they emerge as adults.

Garden weevil adults are slightly bulbous and grey with a light V stripe across the top of the abdomen
Garden weevil adults

Adult garden weevils are grey-brown, about 7 millimetres long, and are flightless. They have a bulbous abdomen with a prominent pale white V stripe across the end of the abdomen.

The adult is similar in appearance to apple weevil, Fuller's rose weevil and vegetable weevil. Another weevil that may be found occasionally in vineyards is whitefringed weevil. To distinguish between adults of garden weevil and these other species, refer to Identifying soil beetle pests.

Adult weevils emerge from the soil in mid to late October and are most numerous during November and early December. Many adults survive until April with some present through winter.

As the weevils are most abundant in spring, they appear to only have one generation each year. However, in some situations there may be two generations.

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Contact information

Stewart Learmonth
+61 (0)8 9777 0167