The vine weevil, scientifically known as Otiorhynchus sulcatus, is a garden and nursery pest whose diet changes dramatically throughout its life cycle. Understanding what this insect eats requires distinguishing between the adult beetle and its larval stage. Both forms feed on plant material, but they target different parts of the plant, resulting in two types of damage. The adult primarily consumes foliage, which is often a cosmetic issue, while the larva feeds exclusively beneath the soil, making it the most destructive stage of this pest.
The Adult Diet: Leaf Damage and Notching
The adult vine weevil is a dark, black beetle, measuring about 9 millimeters in length, that feeds on the leaves of many host plants. These insects are nocturnal, emerging from hiding places after dark to feed. During the day, they remain hidden, often allowing their presence to go unnoticed until damage becomes visible.
A defining feature of the adult diet is the characteristic, irregular, crescent-shaped or C-shaped notches chewed along the edges of leaves. This notching is most frequently observed on broad-leaved evergreens like Rhododendrons and Camellias.
Because the adults only consume the leaf margins, this feeding rarely impacts the plant’s overall health. The plant can tolerate the loss of leaf tissue. Adult weevils are flightless because their wing covers are fused, meaning they must crawl to find food sources and egg-laying sites.
The Larval Diet: Root and Crown Destruction
The larval stage causes the most damage. It is a creamy-white, legless grub that develops in the soil. These C-shaped larvae, up to 15 millimeters long, feed on the plant’s roots. They initially target fine feeder roots, hindering water and nutrient absorption.
As the grubs mature, they progress to feeding on larger structural roots and the plant’s crown. They chew away the outer tissues of the roots and the stem base, a process known as girdling. Girdling severs the plant’s transport system, preventing water and nutrients from reaching the shoots.
This destruction often results in plant death, especially during autumn and spring when the grubs are most active. An infested plant will wilt and collapse, even when the soil is moist, because the root system has been eaten away. This damage often goes unnoticed as the weevil activity is hidden beneath the soil.
Most Targeted Plants and Environments
The vine weevil is polyphagous, feeding on a wide variety of plants, with over 100 species listed. Adult beetles feed on shrubs and herbaceous plants, including Rhododendrons, Azaleas, Hydrangeas, and evergreen Euonymus. The larvae are particularly damaging to plants like Cyclamen, Primula, Heuchera, Begonias, and Strawberries.
Containerized plants are highly affected by vine weevil larvae. The confined space of a pot concentrates the larvae within the root ball. This focused feeding quickly leads to the complete consumption of the root system and the death of the container-grown plant.
Even plants the adult weevils do not feed on, such as Sedum, can still be damaged by the larvae. Adults lay eggs near many plants, and the resulting grubs feed on whatever roots are available, making the pest a threat across diverse garden settings. This affects commercial nurseries and home gardeners who utilize potted plants.