**Nursery Weevils** is a general term often referring to weevil species that are major pests of ornamental plants in nurseries, greenhouses, and landscapes, most notably the **Black Vine Weevil** (*Otiorhynchus sulcatus*) and the **Strawberry Root Weevil** (*Otiorhynchus ovatus*). The conflict is severe and twofold: the adults cause minor, aesthetic **leaf damage** (notching), but the larvae (white grubs) are voracious pests of the plant **root systems**, leading to stunting, wilting, girdling of crowns, and plant death, especially in containerized stock.
Taxonomy and Classification
Weevils belong to the order Coleoptera (snout beetles). They undergo complete metamorphosis. The adults are nocturnal and flightless (in the case of the Black Vine Weevil), making them difficult to detect. Many pest species are **parthenogenetic** (females reproduce without males), which allows populations to build rapidly from a single individual.
Physical Description
Adult Weevils are 1/4 to 1/2 inch long.
- **Adult (Key ID):** Black or dark brown, hard-shelled beetles with a characteristic elongated snout (rostrum). The Black Vine Weevil has small, yellowish-gold hairs on its body.
- **Larvae (Grubs – Key ID):** Creamy white, legless, C-shaped grubs with a brown head capsule, found coiled up in the root ball or soil.
- **Damage Sign (Key ID):**
- **Leaf Notching:** Adult feeding causes characteristic **C-shaped or scalloped notches** chewed out of the leaf margins (edges) of host plants (e.g., Rhododendron, Yew).
- **Root Loss:** Container plants show wilting or sudden death due to the larvae eating the roots and girdling the crown.
- **Conflict:** Severe ornamental and nursery crop loss.
Distribution and Habitat
Nursery Weevils are cosmopolitan. Their habitat is the foliage and root zone of their host plants, particularly favoring those in container nurseries, which offer ideal conditions (dense roots, consistent moisture) for the grubs.
Behavior and Conflict
The conflict is cumulative root destruction.
- **Hidden Damage:** The most destructive stage, the root-feeding grub, is hidden underground until severe plant symptoms appear.
- **Nocturnal Habits:** The adult leaf-notching damage (while minor) occurs at night, making the adult beetles hard to spot, though they can be found by inspecting plants with a flashlight after dark.
- **Girdling:** Large grubs can completely chew around the woody stem just below the soil line, effectively girdling and killing the plant.
Management and Prevention
Control is integrated pest management (IPM), targeting the larval stage in the soil.
- **Nematodes:** Apply **Entomopathogenic Nematodes** (*Heterorhabditis* species) to the soil/potting mix when soil temperatures are warm (60^\circ \text{F}) to target and kill the feeding larvae. This is highly effective in container stock.
- **Larval Treatment:** Apply a soil drench insecticide to target the grubs in the soil, timed for when the larvae are small (late summer/early fall).
- **Adult Treatment:** Apply a residual insecticide to the foliage and ground in the evening to target the nocturnal adults before they lay eggs (less common).
Conservation and Research
Nursery Weevils are managed as high-priority nursery pests. Research focuses on improving the application and viability of beneficial nematodes, developing less-toxic chemical controls for greenhouse/nursery use, and preventing the spread of parthenogenetic species through horticultural commerce.