Black Vine Weevil Fact Sheet
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|Adult black vine
weevil -- Photo courtesy of David Shetlar
| Black vine weevil
larvae -- Photo courtesy
of David Shetlar
|The black vine weevil, Otiorhynchus
sulcatus (Fabricius), is a serious pest in nurseries as well as in
home ornamental plantings in Pennsylvania. While the adult weevils
feed on foliage, often resulting in an unsightly appearance, the
more serious damage is done by grubs (larval stage), which feed
on the roots and may girdle the main stem often killing the plant.
|Black vine weevil
feeding on Wintercreeper Euonymus, Euonymus fortunei
-- Photo courtesy of Michael Masiuk
Adult will feed on over 100 different kinds of trees, shrubs,
vines, and flowers in Pennsylvania landscapes. They have a strong
preference for Taxus (yews), and various species of rhododendrons,
but can also be found on Tsuga (hemlock), Pieris japonica (Japanese
andromeda), Euonymus, Kalmia (mountain laurel) and Ilex crenata (Japanese Holly). Occasionally, this pest will feed on herbaceous
plants including houseplants placed outside during the summer.
Adults are 3/8" long, oblong-shaped, with a short snout, and
elbowed antennae. Their bodies are a dull, slate gray to brownish-black
color, and their wing covers have numerous small pits with small patches
of short golden hairs. All adults are female and unable to fly. The
legless, C-shaped larvae are cream colored with shiny brown heads
and measure 5/8" long at maturity. Black vine weevil eggs, which
are initially white but turn brown as they mature, are laid in the
soil or leaf litter at the base of the affected plant.
||Immature larvae spend the winter in the soil. On occasion, adults overwinter.
||In early spring, the larvae mature and feed on roots. The larvae pupate inside an earthen chamber before emerging as adults from late May through June. Adults weevils must feed on plant material for 21-45 days prior to egg laying.
||Adults begin egg laying in July, depositing an average of 200 eggs in the soil or leaf litter during their 90-100 day lifespan. Eggs hatch in 2-3 weeks and the larvae begin to feed on small plant rootlets. As larvae mature, they begin to feed on larger roots and underground stems.
||Maturing larvae continue to feed on roots until the soil temperatures drop, signaling them to move deeper in the soil, where they overwinter.
Look for the characteristic marginal notching on new foliage. The
injury is easier to spot on broad-leaved evergreens, such as rhododendron,
and more difficult to find on narrow-leaved ones, such as Taxus (yews). Monitoring should be directed to the lower foliage. Since
the weevils crawl and cannot fly, the foliage onthe lower portion
of the plant will be injured first. Black vine weevil adults feed
at night and hide at the base of plants during the day. Placing a
6" x 6" board on top of the mulch beneath the affected plant
or loosely wrapping a piece of burlap around the stem will provide
a place for the adults to hide and can be checked easily during the day to
determine early season adult activity.
||The entomopathogenic nematodes, Steinernema and
Heterorhabditis spp., have been effective for controlling larvae,
especially in potted plants. Sufficient water must be used during
application to wash the infective nematodes into the soil and root
zone. Applications of these nematodes in landscapes have produced variable
||Hand removal of adults can be effective
when utilizing the 6" x 6" board or burlap, especially on small plantings
or individual plants.
||Egg and larval survival are helped when soil moisture
is moderate to high in July and August. Heavy mulches also help maintain
critical moisture levels. Remove excessive mulch layers and do not
water plants unless necessary. Excessively damp soils in the fall
also force larvae to move up the base of the plant where girdling
||Some rhododendrons show resistance to weevil feeding.
Varieties with a rolled leaf edge may be difficult to weevils to feed
||Treat for the adults 2-3 weeks after emergence (before
egg laying occurs). Apply the insecticide thoroughly to the plant
and a surrounding two foot radius of soil. Because the adults emerge
over an extended period of time, a second foliar spray should be applied
three weeks after the first application was made. (Insecticides
labeled to control Black Vine Weevil in Pennsylvania)
Black Vine Weevil Fact Sheet
Authored by: Michael Masiuk, Commercial Horticulture
Extension Agent, Allegheny County, Pennsylvania
Last Updated: Tuesday, February 11, 2003