Download Home-Invading Root Weevils

OC0403
Michigan State University Extension-Oakland County
Home-Invading
Root Weevils
The strawberry root weevil (Otiorhynchus
ovatus), the black vine weevil (O. sulcatus), the
rough strawberry root weevil (O. rugosotriatus),
and the Sciapilus weevil may become
household nuisance pests because of their
tendency to invade homes in summer and fall.
None of these weevils attack foodstuffs,
furnishings or woodwork, nor are they
dangerous to humans or pets. They are strictly
a nuisance invader.
IDENTIFICATION
The adult root weevils are snout beetles with
hard-shelled bodies and rows of small round
pits on the wing covers.
The strawberry root weevil is ¼ inch (5-6 mm)
long and brownish-black with a short, blunt
snout protruding from the front of the head.
The rough strawberry root weevil imported long
-horned weevil and clay-colored root weevil
may invade the home in considerable numbers.
The black vine weevil is shaped like the
strawberry root weevil except larger – ½ inch
long (10-12mm). The wing covers have small,
scattered patches or whitish or yellowish hairs.
The immature feed on the roots of many
evergreens and shrubs.
The Sciapilus weevil is mostly a problem in the
upper Peninsula. They are 8 mm in length and
more slender than the preceding weevils. The
body is tannish-gray with a slightly lighter
colored head. This weevil is also associated
with strawberries. It is often first seen in May
and attempts to control it should be made at
this time.
LIFE CYCLE AND HABITS
Adult root weevils are unable to fly because the
wing covers are joined. These flightless adults
are females that develop from unfertilized eggs.
Host
plants
include
taxus,
hemlock,
rhododendron, primrose, strawberry, raspberry,
loganberry, grape, azalea, red clover, grass,
and many other nursery and flower garden
plants. Damage is caused by the larvae
devouring the roots and the adults feeding on
the leaves.
The life cycles are similar, with most spending
the winter as nearly grown larvae in the soil
among roots of the host plants. They change to
pupae in the spring, emerge as adults in June
and begin laying eggs near the crown of plants.
Hatching occurs in about 10 days, and tiny
larvae burrow into the soil to feed on the roots.
There is usually one generation per year. The
strawberry root weevil begins to migrate into
homes in early to mid July and for one or two
months afterwards may be found in cupboards
and bathtubs and on walls and ceilings.
CULTURAL
METHODS
(NON-CHEMICAL)
CONTROL
Because adult root weevils do not fly, they can
only gain entry into buildings by crawling or by
hitchhiking on plant materials. Be sure to caulk
cracks tightly. Special stripping around
doorsills, 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
attached to water and can be trapped in
shallow pans of water placed around house
foundations. Removal of wild strawberries,
brambles and other host plants may help
reduce annoying weevil populations.
Control of weevils inside the home is more
difficult. They are usually found in widely
scattered places, so it would be difficult to use
an insecticide. Therefore, it is best to remove
the offending beetles with a vacuum cleaner or
a broom and dustpan. They like moist places.
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
do even a third application three weeks later if
nuisance weevil populations persist or
reappear. Be sure to read and follow the label
directions.
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 form these plants,
plus many others. They are active at night only.
Euonymus is a favorite. To protect plants, use
a labeled pesticide in early June and follow with
three to four more sprays at three week
intervals. Spray plants thoroughly and wet the
soil underneath them.
CHEMICAL CONTROL METHODS
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
containing carbaryl (Sevin), malathion or
diazinon, giving special attention to the sides
Would you like additional information?
Additional information is available on-line. Please see MSU Extension-Oakland
County’s publications as well s MSU Extension’s Bulletin Office on campus.
Contact our Plant & Pest Hotline (248/858-0902) for assistance with plant
identification, pests and diseases, weeds, trees and shrubs, lawn, flowers,
fruits, vegetables, grasses and groundcovers, native plants, plant propagation,
and many other gardening topics.
Distributed by MSU Extension-Oakland County, 1200 N. Telegraph Road, Pontiac, MI 48341, 248/858-0880,
www.msue.msu.edu/oakland
MSU is an affirmative-action equal opportunity employer. Michigan State University Extension programs and materials are open to all without regard to race, color, national origin, gender, gender identity, religion, age, height,
weight, disability, political beliefs, sexual orientation, marital status, family status or veteran status.