If you are looking for a guide that will help you get rid of vine weevil, you have landed on the right page.
Perhaps, the lone weevil you have ever heard of is the boll weevil, i.e. Anthonomus grandis.
This one is infamous for devastating cotton fields in the United States in the early 20th century.
However, you may neglect another better only at your own risk: the black vine weevil.
In fact, according to historical interests, experts advise the average gardener to pay more attention to the black vine weevil, Otiorhynchus sulcatus.
Moreover, this one is native to Europe, than to its better-known relatives.
This weevil uses a host for a number of plants popular in landscaping, which can cause unsightly, albeit, not life-threatening damage.
However, worst yet, the attacks of its larvae tend to take place at the root level, in some cases, inflicting lethal damage.
It is important to note that the pest is found throughout much of southern Canada and the northern United States.
Find out more about the black vine weevil.
What Does Black Vine Weevil Look Like?
It is important to note that the black vine weevil is an insect that tends to have a gray or dull black color and is about 3/8 inch long.
Moreover, it tends to have a pear-shaped body that is covered in pit marks and has six legs.
Two antennae tend to protrude far out from the head and the snout is also prominent.
Another important thing to note is that black vine weevil does not fly, it gets around by walking.
These pests start out as larvae or grubs, that tend to resemble the grubs of better-known beetles like June Bugs, Phyllophaga longispina, and Japanese beetles, Popillia japonica.
These larvae are worm-like, have no legs, are 1/2 inch long, and tend to take the shape of the letter C.
Furthermore, their bodies tend to be white, with reddish-brown heads.
Sings of Balck Vine Weevil Infestation
It is important to note that the adult black vine weevil tends to be very active from mid-spring to late summer.
Their grubs tend to stay around for a longer time, i.e. mid-summer to the following spring.
Moreover, adult black vine weevils tend to eat the leaves of the plants during the night, and they tend to leave behind a crescent-shaped hole along the leaf margins.
This damage mars the appearance of the plant, however, it is unlikely to result in any serious health consequences to the plant.
On the other hand, the larvae tend to eat the roots of plants and can grindle their lower stems.
This damage tends to cut off necessary water and nutrients moving from their sources to the above-ground growth of the plant.
The damage they do to the plant is more serious than the one the adults will do.
Also, the damage they inflict tends to cause the plant to wither and turn brown, it can even result in the death of the plant.
Due to this destructive activity in the larval stage, an alternative common name for this species is ‘root weevil’.
During May and June, make sure to look for the damage caused by the adult black vine weevil on known host plants.
For instance, grapevines, ir Vitis spp. are a well-known target of these pests, thus, the ‘vine’ is the common name.
As the larvae also produce visible signs of damage on affected plants, you can wonder why we let the detection of their damage serve as an indicator of a black vine weevil infestation.
The reason tends to be two-fold: grub activity tends to take place underground, so you are unable to see them, and by the time the impact of larval feeding is visible at the surface, much of the damage to the plant will have already occurred.
Also, it is irreversible for the garden of the year.
However, if you tend to inspect the plants carefully going forward and find, in a timely manner, the adults that develop from the larvae, act promptly to eradicate them.
Thereby keeping them from laying eggs.
Doing so will help to prevent the emergence of another generation and save the next year’s garden.
Causes of Black Vine Weevil Infestation
As black vine weevils do not fly, they will not cover much territory on their own.
However, they can exploit human activity to travel a number of miles surreptitiously.
That potted plant you tend to buy at a garden center might be a Trojan Horse, with larvae that are present in the root ball.
When the larvae tend to mature, they can spread to other plants on your property.
Make sure to try to buy your potted plants only from reputable nurseries.
You may have to pay more, however, it is worth it.
This is because reputable nurseries are more likely to treat the soil that they use to prevent black vine weevil, you have just bought or planted in the ground.
They also tend to inspect the root area for grubs first and kill any that they find.
4 Ways to get rid of Black Vine Weevils
The best approach to control this pest is to know what causes behind infestation and take preventive infestation, accordingly.
However, in case if it is too late for that, they are a few ways to get rid of this pest.
Handpicking: As adult black vine weevils are nocturnal, looking for pests themselves is not the easiest way to find an infestation.
However, it is one option in case you do not mind wielding a flashlight and inspecting the leaves of known host plants on a few nights in May and June.
If you find any weevils, you can pick them off the foliage and kill them.
Pesticides: If you do not mind using pesticides in your garden, a systemic kind is your best bet.
A systemic pesticide that tends to be effective against both black vine weevil adults and their larvae is imidacloprid.
Apply it at the ground level with water so that the soil around the plant become drenched.
Make sure to follow label instructions and mix the imidacloprid in a bucket with water.
The amount of imidacloprid to use depends on the height of the plant.
Traps: There are a number of traps that are effective for getting rid of this pest.
Some you can make yourself, while others are available at home improvement stores.
For instance, a homemade trap you can make that puts it to good use is an old piece of burlap laying in the corner of your garage.
At the end of the day, wrap the trunks of evergreen plants that the pests attack like the hemlock tree with the burlap, in anticipation of nighttime feeding.
The beetle tends to use such material for shelter.
In the morning, you will need to inspect the burlap for pests and kill any black vine weevil you find in it.
While an example of a store-bought trap is Tanglefoot, which you will wrap around the trunk of a host tree or shrub.
This product tends to work on the same principle as the flypaper that you use indoors.
Predators: Another way to avoid any major infestation while staying organic in addition to handpicking and traps is to use predators for these pests.
It is important to note that pests can kill the larvae before any further plant damage takes place if the application occurs in a timely manner.
In this case, the predators are parasitic nematodes, Heterorhabditis bacteriophora.
You can find them through online biological control businesses.
Moreover, it is important to note that nematodes can be both good, and bad, and in this case, they can help you to fight a pest.
Just like a systemic pesticide, this method ‘gets to the root of the problem’.
The nematodes are drenched into the soil beneath the host plants, and make sure that your soil is sufficiently well-drained to receive them properly.
The best application time is when this pest larve is first expected to be present, which is in the mid-summer.
You will need to apply the drench in the early morning or in the evening.
The ground in the area should be watered before the application to make it evenly moist, and make sure to keep it evenly moist for at least 2 weeks after application.
Preventing Black Vine Weevil Infestation
Even if black vine weevil larvae were to find their way onto your property, there are certain ways to thwart or at least impede the adults that develop from them.
Moreover, the best way to deprive them of the host plants that they feed on for sustenance.
Places that are commonly attacked by the black vine weevils are:
- Hosta (Hosta spp.)
- Euonymus (Euonymus spp.)
- Hemlock (Tsuga canadensis)
- Mountain laurel (Kalmia latifolia)
- Azalea (Rhododendron spp.)
- Yew (Taxus spp.)
In case you tend to love one or more of these known host plants and decide that you need to take the risk and grow them in your yard, there is still a way to slow down the attacks that will come from the black vine weevils.
This tactic tends to take advantage of the fact that this pest cannot fly.
Make sure to simply prune the branches of the known host shrub, like the mountain laurel, growing in mass or with other plants, creating spaces between vegetation.
Moreover, doing so will help eliminate the ‘bridges’ that black vine weevils will need to move from one plant to another.
In the same way, as much as you may like the look of a branch arching down to the ground, prune off such branches on known host plants so that these pests cannot climb them to access your plants.
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