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Vegetable beetles

Agronomist, Cam Conboy (Gorst Rural), has observed extremely high numbers of adult vegetable beetles (Gonocephalum sp.) in two wheat paddocks near Tatyoon, in the Western district of Victoria. Cam says the beetles are particularly abundant in bare patches within the paddocks (e.g. along wheel tracks). The presence of vegetable beetle adults in spring is not unusual and is generally not of concern. Vegetable beetles typically attack germinating crops in autumn.

Vegetable beetle larvae are minor pests of winter cereals, while the adults can attack emerging canola seedlings. The adults can occasionally attack spring-sown crops, such as sunflowers. Typical damage includes chewing seedlings at or above ground level, ring barking plants or completely cutting stems. Despite the high beetle numbers, Cam says no feeding damage to wheat plants in either paddock has been observed.

Vegetable beetles (sometimes referred to as ‘false wireworms’) usually have one generation per year, with adults emerging in spring. Common species are 6-10 mm long, and have a dark grey-black coloured body, which is oval-shaped and often covered in soil. Larvae are elongated, hard-bodied, cream, yellow or tan in colour, with three pairs of legs just behind the head. The body is cylindrical and up to 20 mm in length. Click here for images of vegetable beetles.

In recent years there has been an increase in reports of vegetable beetles attacking crop plants in many regions of south-eastern Australia. It is unclear exactly what has triggered this increase. High populations are often associated with patches of high plant residues. Factors including temperatures > 20°C, moisture stressed crops, and light, dry soils have also been associated with cases where vegetable beetles have been found attacking crops.

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