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Root weevils are larvae of snout nosed beetles – usually flightless and all females – that feed on roots of a wide range of plants. Several species can be serious pests in nurseries and greenhouses. Some root weevil pests include the black vine weevil, strawberry root weevil, rough strawberry root weevil, clay colored weevil and woods weevil. Depending on the species, adults range from 1/5 to 1/2 inch long.

Root weevils will spend the winter as adults in some parts of the U.S, but in most areas root weevils winter as larvae in the soil. Larvae pupate and adults of many species emerge in early to late spring – in greenhouses emergence can be much earlier. In the Pacific Northwest, adults can emerge well into summer. Adults need to feed on plants for 3 – 6 weeks before beginning to lay eggs. Adult weevil injury usually appears as semicircular notches on leaf margins. Developing buds may also be damaged. Feeding occurs at night. Adults can remain active for several months.

Eggs are laid in the soil or in debris near host plants. Larvae feed on roots and root hairs, passing through five or six instars. Older larvae may girdle entire stems. Larvae have brown heads, are usually white to cream colored, legless and C–shaped. Injured plants in nurseries and greenhouses may die suddenly. Outdoors there is one generation per year. In greenhouses there may be two generations.

Discus(TM) - Nursery Insecticide
For control of root weevil adults and larvae, apply 3.4 to 5.6 fluid ounces per 1000 ft2 as a banded spray to the soil surface, followed by irrigation or rainfall to move the active ingredient to the root zone; OR apply .75–1.5 fluid ounces per inch of trunk diameter (at breast height) or per foot of shrub height. Use a minimum of 10 gallons of water per 1000 ft2 as a drench; OR mix 13 fluid ounces (385 ml) in the appropriate amount of water for containers (see label). Apply when adults are laying eggs to target the very young larvae.

Apply 25 fluid ounces per 100 gallons as a foliar spray to target adults. Apply when feeding injury first appears.

Marathon® II - Systemic and Translaminar Insecticide
For control of root weevil adults and larvae, apply 1.7 fluid ounces in the appropriate amount of water for smaller containers (see label), or 0.1–0.2 fluid ounces per inch of trunk diameter (at breast height) or per foot of shrub height. Use a minimum of 10 gallons of water per 1000 ft2 as a drench. Apply when adults are laying eggs to target the very young larvae. Shake well before use.

Marathon® 1% G – Systemic Insecticide
Marathon® 1% Granular systemic insecticide is applied topically to the growing media or incorporated prior to planting. Media incorporation has provided excellent root weevil larval control. Apply when adults are laying eggs to target the very young larvae.

Azatin® XL – Insect Growth Regulator
Apply 21 fluid ounces per acre as a foliar and soil application for larval control. The pH of the spray solution should be maintained between 3 and 7. For best results use a spray adjuvant. Repeat applications at 5–7 day intervals. Always read the label.