Ohio State University Extension Fact Sheet

Ohio State University Fact Sheet

Entomology

1991 Kenny Road, Columbus, OH 43210-1000


Root Weevils and Their Relatives

HYG-2069-95

William F. Lyon

Common Name Scientific Name
Black Vine Weevil Otiorhynchus sulcatus (F.)
Rough Strawberry Root Weevil Otiorhynchus rugosotriatus (Goeze)
Strawberry Root Weevil Otiorhynchus ovatus (L.)
Imported Longhorned Weevil Calomycterus setarius Roelofs
Asiatic Oak Weevil Cyrtepistomis castaneus (Roelofs)
Tulip Tree Weevil Odontopus calceatus (Say)

Several kinds of adult root weevils and their relatives may crawl or hitchhike into homes and other buildings, sometimes in relatively large numbers. Although annoying and a pest by their presence, they do not bite or harm humans, domestic animals (pets), structures, furnishings or foods. Some feel many beetles migrate in search of moisture and hibernating quarters. They invade the house accidently and usually do not live indoors over a few days. However, occasionally a few adults may hide and overwinter. Adults do not fly and males are not required for successful reproduction.

Identification

Adult weevils (shaped like a pear or light bulb), known as "snout beetles," have hard-shelled bodies with rows of small round pits on the wing covers. The head extends downward into a curved, short, broad snout with long antennae (usually elbowed and clubbed) inserted in the sides. Beetles are oval-like, elongated, cylindrical or rather flattened, usually covered with a dense coating of scales. The abdomen (rear part) is rounded. Mouthparts are located at the end of the snout. Legs are often short or long with wings developed, reduced or lacking. Hard wing covers normally cover the abdomen. Larvae are C-shaped, smooth or wrinkled, robust with a few hairs and usually legless.

Black Vine Weevil Rough Strawberry Root Weevil Strawberry Root Weevil

Black Vine Weevil

Adults are about 1/3 inch long, black with patches of yellow scales, have wing covers with coarse, strial punctures and cannot fly. No males have been observed. There is one generation per year outdoors. Eggs are deposited without fertilization (parthenogenesis) on the soil of host plants during July and August. After eggs hatch, white or pinkish larvae with brown heads burrow into the soil and feed on plant roots. They overwinter as well-grown larvae in the soil, pupate in late May or early June with new adults appearing in June and early July. Adults feed on the foliage at night and hide during the day in debris and loose soil under host plants. Severe injury to Taxus occurs in northeastern Ohio at nurseries, sometimes with hundreds of Taxus plants killed by root feeding larvae after growing to the stage where they were sold for landscaping purposes. Injury occurs on rhododendrons and azaleas primarily by adult foliage feeding and by larval feeding on the crown and roots. Other hosts include grape, strawberry, blackberry, blueberry, cranberry, etc. Although a major pest of woody ornamentals in commercial nurseries, they cause occasional injury in greenhouses where Taxus plants are being propagated by both adults and larvae. Beetles can crawl into houses and other structures, causing alarm by homeowners.

Rough Strawberry Root Weevil

Adults are slightly more than 1/4 inch long and resemble the strawberry root weevil and black vine weevil except for size. They are black, shiny, without scales and with coarse, strial punctures on the wing covers. Adults are common on fruit trees in June. It has not been a serious pest of strawberries in Ohio, but may occasionally enter residences for hibernation. Adults feed at night and hide during the day.

Strawberry Root Weevil

Adults are about 1/5 inch long, shiny black with thinly scattered yellowish short hairs (pubescence), reddish-brown antennae and legs, and coarse, deep, strial punctures on the wingless wing covers (wings fused together). No males have been found. They feed at night on leaves and berries, crawl rapidly (they cannot fly) and, sometimes in late summer and autumn, appear on sides of houses and within houses in large numbers. They may crawl throughout the house from baseboard to the ceiling, dropping to the carpet and repeating the process. They hide in clothing, bedding, carpet or appear in sinks, bathtubs, drains and other places where moisture is present. Outdoors, adults feed on leaves and larvae on plant roots and between them both, injure, weaken and sometimes kill the plants. Larvae especially injure roots of hemlock, spruce, Taxus and arborvitae in nurseries and plantations. Other hosts include strawberry, raspberry, grape, apple, peach, etc. The white muscardine fungus, Beauveria bassiana is important in controlling this troublesome weevil.

Imported Longhorned Weevil

Adults are about 1/4 inch long, gray with irregular tan markings, rounded abdomen, white scales with short blunt hairs on the wing covers and long, prominent antennae. Adults emerge from the soil in late June and become abundant during July and August. These wingless, parthenogenetic (development from unfertilized eggs) adults feed on a wide variety of foliage including alfalfa and red clover. When abundant, they crawl on humans, vehicles and in dwellings on walls, ceilings, furniture or even food on tables. Both this weevil and the strawberry root weevil can cause complaints by many homeowners.

Asiatic Oak Weevil

Adults appear similar to the imported longhorned weevil in size and shape distinguished by iridescent blue to green scales and pointed hairs. Adults are strongly attracted to lights where they may invade homes as a result. Hosts are red, scarlet, white and pin oaks. Alfalfa is sometimes infested.

Tulip Tree Weevil

Adults are about 3/16 inch long, black-colored, large prominent eyes and a curved snout. Homeowners confuse adults with ticks except ticks do not fly and these weevils do and are attracted to lights. Weevils overwinter in protected places and females insert their eggs in the midrib of host tree leaves in mid-May. Larvae mine leaves of magnolia, sassafras and tulip popular until pupation in the midrib with adults appearing in large numbers in June. New adults feed a week or more before aestivation.

Control Measures

Prevention

Since some adult weevils do not fly, they can only gain entrance into buildings by crawling or hitchhiking on plant materials. Be sure to caulk cracks tightly. Special stripping around door sills, windows and other potential points of entry may be needed. Snug fitting screens and doors will reduce the number of weevils crawling into a building.

Weevils are strongly attracted to water and can be trapped in shallow pans of water placed around the house foundations. Removal of wild strawberries, brambles and other host plants may help reduce annoying weevil populations.

Since some weevils are attracted to lights, subdue the lighting around the windows and doors by using less-attractive yellow light bulbs. Avoid excessive lighting directly upon the house when weevils are prevalent. Indoor lights should not shine directly out of door or window openings. Colored walls that do not reflect light are preferable to glossy white.

Plant Protection

Black vine weevil larvae damage the roots of Taxus, azalea, rhododendron, hemlock red maple, spruce and Douglas fir. Adult weevils eat notches out of leaves from these plants, plus many others. Euonymus is a favorite. To protect plants, use acephate (Orthene) insect spray in early June and follow with three to four more sprays at three-week intervals. Spray plants thoroughly and wet the soil underneath them. Other larvicides include oxamyl 10G, Turcam 76% WP and Steinernema carpocapsae. (Follow label directions and safety precautions.)

Inside the House

Collect individual adult weevils with a strong suction vacuum cleaner or broom and dustpan and discard. It may be difficult to treat with an insecticide because weevils may become widely scattered throughout the house. They like moist places.

Outside the House

At the first sign of adult weevil activity or by late June, spray the outside foundation of the building with an insecticide for crawling insects such as acephate (Orthene), carbaryl (Sevin), chlorpyrifos (Dursban) or diazinon, giving special attention to the sides and bases of steps and porches, around doorways, around basement windows, and at other potential points of entry. Also, treat the grass away from the foundation for 10 feet. Repeat the applications again in mid-July, and repeat a third application three weeks later if nuisance weevil populations remain. Be sure to read and follow the label directions and safety precautions.


All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.

Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension.

TDD No. 800-589-8292 (Ohio only) or 614-292-6181



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