Vegetable Weevil
Listroderes costirostris
📖 Description
The vegetable weevil is a flightless, parthenogenetic snout beetle of South American origin that has become established in warmer regions worldwide. All individuals are female, and each can reproduce without mating, allowing rapid population buildup from even a single introduction. Both adults and larvae are pests — adults feed nocturnally on foliage, creating characteristic notches along leaf margins, while larvae feed on roots and stems at or below the soil surface. They are particularly damaging to young vegetable transplants and root crops, and can be difficult to detect because of their nocturnal habits and subterranean larval feeding.
⚠️ Symptoms to watch for
- C-shaped notches chewed from leaf margins
- Larvae feeding on roots and crowns at soil level
- Wilting and collapse of young transplants
- Ragged holes in foliage from adult nocturnal feeding
- Girdled stems near the soil surface
🩹 Treatment
- Hand-pick adults at night when they are actively feeding (organic)
- Apply beneficial nematodes to soil for larval control (organic)
- Use spinosad-based sprays applied in the evening for adult control (chemical)
- Apply bifenthrin or permethrin as a border treatment (chemical)
🌿 Organic treatments
- Hand-pick adults at night when they are actively feeding
- Apply beneficial nematodes to soil for larval control
🧪 Chemical treatments
- Use spinosad-based sprays applied in the evening for adult control
- Apply bifenthrin or permethrin as a border treatment
🛡️ Prevention
- Rotate crops to non-host plants to reduce resident populations
- Cultivate soil in fall to expose larvae and pupae to predators and weather
- Use floating row covers on young transplants until established
- Remove crop residues and weed hosts after harvest
🪴 Affected plants
- Tomatoes
- Potatoes
- Carrots
- Turnips
🦋 Natural predators
- Birds
- Ground Beetles
- Spiders
- Parasitic Nematodes
🌱 Host plants
- Solanum tuberosum
- Solanum lycopersicum
- Daucus carota
- Brassica rapa
🔄 Lifecycle
- Vegetable weevils have one generation per year.
- They overwinter as adults in protected locations such as plant debris and soil crevices.
- Adults become active in early spring and feed for several weeks before laying eggs on host plants or in soil.
- Larvae feed for 6-8 weeks before pupating in the soil.
- New adults emerge in midsummer, feed briefly, then enter a summer aestivation period before becoming active again in fall.
- All individuals are female, reproducing by parthenogenesis.
📅 Season
- Spring to Fall (most active in spring and fall)
🔎 Appearance
- Vegetable weevil adults are small, greyish-brown snout beetles with a distinctive elongated snout and a mottled appearance from light and dark scales covering their body.
- They have a broad, oval shape and appear somewhat hunchbacked when viewed from the side.
- The wing covers have shallow grooves and are often marked with a faint V-shaped lighter band near the middle.
- Larvae are legless, creamy white with a brown head, and feed concealed within plant tissue or at the soil surface.
💥 Damage level
- Moderate
🔁 Reproduction rate
- Moderate
🗺️ Geographic regions
- South America
- Southern North America
- Australia
- New Zealand
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