VANDALIZING LEAVES AND ROOTS, CAUSING HARM TO INNOCENT
Bandit; Snout Beetle, Black Vine Weevil, Clay Colored, Root Weevil, Otiorhynchus
spp.; Obscrue Root Weevil, Sciopithes spp.
Hangout: Berry plants and ornamental plants; especially
Physical Features: Young bend their bodies
into c-shapes, are plump and usually legless with white bodies and brown
heads; adults are 1/4" - 1/2" beetles with long protruding noses
and pear-shaped bodies with gray, black or brown coloring
A root weevil's ruthless assault is from top to bottom. Larvae hatch from
eggs laid in the soil or, in the case of the obscure root weevil, from
eggs laid on leaves. These murderous munchers spend the winter eating
plant roots, weakening them. In mid-spring, the young deviants mature
into adult offenders, continuing the assault by climbing up the trunk
and chomping on leaves, usually at night. They make a characteristic notching
pattern, vandalizing the edges of the leaves. Most root weevil species
are all female so they reproduce by cloning in the summer.
MOST SPECIES OF ROOT WEEVIL ARE TRUE FEMMES FATALES, WITH NOT EVEN ONE
MALE LEFT IN THEIR MIDST.
1. Patrol the area
- Kick dirt away from the
plant base. Scout the crown of the roots for bite marks.
- Stake out suspicious areas
at night, using a flashlight to look for adults eating leaves. Check
leaves close to the ground. Different species begin feeding at different
times in the growing season. The earliest weevils begin in early spring.
- Look for notched edges of
leaves. Notches may be from a previous invasion, so record where you
see notches and check for new bites, or bites on new leaves.
2. Make a positive I.D.
- Check out adult beetles.
Soil-dwelling larvae are harder to identify. Don't confuse them with
predaceous ground beetles, which are good guys.
- In general, adult root weevils
are pretty easy to identify, but figuring out the exact species is difficult.
It's essential to research the correct species because information you
find about one type of weevil is not necessarily true for other types.
Let a trained eye help you out at the Cooperative Extension office.
3. Do a thorough background
- Get to know the habits of
each life stage. Adults are mostly active at night, so this would be
a good time for S.W.A.T. missions.
4. Determine the danger
- Plants can handle some damage
from weevils. Bites out of leaves are ugly, but bites out of roots are
more harmful. Check the root crown for damage.
5. Make a plan.
- Do-Nothing Method
Inspect new leaves closely for notches-good clues for determining population
size. If no newnotches appear, you don't need to do anything.
- Manipulative Measures
-There's nothing better than S.W.A.T.! Handpick weevils off plants at
night or whenever you see them. They are hardened criminals, so be prepared
to expend some energy cracking 'em. Or if you prefer, place a white
sheet under the plant, shake vigorously, and dump apprehended weevils
into a bucket of soapy water.
-Don't mulch over the root crown. Young weevils that eat underground
roots can hide under the mulch and could nibble the plant to death.
-Trap rascally root weevils in sticky roadblocks around tree trunks.
You can buy kits at a garden store. Just wrap tree gauze or tree bands
around the trunk, apply a 3-4" wide band of the sticky stuff, and
replace it after it's filled with weevils or not sticky anymore. It's
not expensive, less toxic than insecticides, and effective!
-Purchase plants that can hold their own against weevils. See Passive-Aggressive
Plants for a list of resistant or tolerant rhododendrons.
- Secret Agents
-Ground beetles and other predators will hungrily devour weevils.
-Send in squads of parasitic nematodes, micro-worms that'll destroy
weevils. Follow directions for use, storage, and disposal carefully.
Not doing so could mean death for your helpers. Locate suppliers through
Cooperative Extension, garden stores, or the Internet.
- Armed and Dangerous
-Chemical weapons are not effective against all types of root weevils.
Be sure you know species you have before you arm yourself.
-If you must use chemicals, spray leaves in the evening since weevils
get the midnight munchies. Spray before adults lay eggs, which is usually
by June, but it depends on the species. Only spray leaves of assaulted
-When using chemicals, follow directions for use, storage, and disposal.
6. Evaluate the results
- Root weevils may leave the
scene of the crime quickly, but the bite marks they leave behind are
essential evidence. Document bites on roots, notches in leaves, and
the size of their mob. Also note if you did anything that may have made