Monday, February 25, 2013

Pest #5 - The Root Weevil

Thanks for keeping up with the worst garden pests of all time.  If you missed the beginning of this series, you can check it out from the beginning here.

Pest #5 is the Root weevil.  

Root Weevil

The root weevil likes to hang out in berry plants and ornamental plants; especially rhododendrons
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.

Uproot, Weevil!

Here's what you can do to kick these buggers to the curb:
1. Kick dirt away from the plant base. Scout the crown of the roots for bite marks.
You'll have to do some sleuthing at night since these guys are nocturnal.  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. 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.

3. Get to know the habits of each life stage. Adults are mostly active at night.

4. Determine how badly you are infested. 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. Determine what your plan is.  Will you do nothing or call in the swat team, aka, your local tree service that offers plant health care?
Start by inspecting new leaves closely for notches-good clues for determining population size. If no newnotches appear, you don't need to do anything.
-Handpick weevils off plants at night or whenever you see them. One method to get rid of these pests is to 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.
Here are a few things you can do to control the weevil problem
-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 garden stores, or the Internet.
For a more serious problem, here are a few measures you can take.
-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 plants.
-When using chemicals, follow directions for use, storage, and disposal. 

6. How well did you do?  Are the root weevils gone?
Root weevils may leave 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 them scram.
Stayed tuned for more on pests later this week.

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