Warm temperatures and blossoming buds get us all moving. But when everything beautiful is bursting to life, so are bugs and pesky pests. These little invaders can cause serious damage to your trees, and it won’t be long before you see your favorite tree losing its charm.
With a wide variety of wood-borers and leaf-eaters out there, you need to know the tell-tale signs of pest infestation and understand how to stay ahead of these tiny creepers.
The 8 most common pests that can attack and damage your trees include:
Let’s break them down and explore each pest’s life cycle, host trees, and the right approach to deal with them.
Sap-suckers
Aphids
These soft-bodied insects usually exist in colonies and are not seriously harmful to healthy trees. Aphids attack your tree’s luscious leaves, eat away all the sap from the stem, and leave behind honeydew, which is a sticky syrup-like substance. They mainly attack fruit trees, willows, pines, maples, oaks, poplars, etc.
Aphids may develop wings in their fully mature state and can range from 1/16 to ⅛ inches in length. You can easily tell them apart from other tree pests by their tail-like ends. Aphids lay eggs in the fall that hatch in the springtime. So, if you have an aphid outbreak, it’s safe to assume that you would be dealing with a huge number.
How to tell if you have an aphid infestation
You can spot little aphid bugs crawling on the leaves and stems of your tree. Severe infestations might cause leaves to curl or become misshapen. Honeydew will also allow sooty mold to develop on the undersides of leaves.
Other signs of an aphid invasion include dead plant shoots, stunted growth, and yellow foliage. If you have lawn furniture or a car under an infested tree, you would find them covered in a sticky fluid from the aphid secretions. It’s a sweet goo that also attracts ants.
How to get rid of aphids
Mostly, aphids are nothing to worry about unless you see them engulfing your plant in large numbers. If that’s the case, simply hose off the tree with a strong stream of water.
If you are dealing with a heavy infestation, use an insecticide soap or a natural pesticide that dehydrates the insects and kills them a few hours later. You can also use neem, horticultural oils, or botanical insecticides.
How to prevent aphids
Early detection can save you and your tree a lot of stress. Examine your trees weekly. Check the undersides of new leaves and buds for colonies or clusters of aphids. Remove them by pruning branches, or crush aphids by hand. A few more tips to keep aphids at bay include:
- Plant onions or members of the onion family because aphids are repelled by their smell.
- Grow plants that attract predatory insects to discourage or trap aphids. Soldier beetles, ladybugs, hover flies, spiders, big-eyed bugs, hornets and many other kinds of bugs feed on aphids.
- Regularly weed around trees.
Whiteflies
Whiteflies, also known as snow flies, are tiny insects that love to feed on the undersides of leaves. Whitefly larva look like a scale insect with a flattened oval shape, while fully mature insects resemble small moths. The wings and body of the adult whitefly are covered in a powdery white wax, too.
These pests excrete a sticky substance called honeydew that causes sooty mold to develop. They are also known to transfer plant viruses, and that’s when they pose a real danger to your trees. Broadleaf trees and shrubs, including citrus, Bradford pear, ash, and flowering fruit trees are common hosts for whiteflies.
How to tell if you have whiteflies
The easiest way to detect whiteflies is to check under the leaves. Whiteflies congregate around the veins and new growth, so examine those unfurled leaves, too. You will notice little white bugs flying away in swarms as you approach the plant.
You can also tell something is amiss from the sticky substance whiteflies leave on leaf surfaces. If they are present in large numbers, your trees and shrubs will have silvering, yellowing leaves, and general discoloration and distortion. Whiteflies usually attack fruit trees, and ornamentals.
How to get rid of whiteflies
The simplest way to shoo them away is with a hose or a spray bottle. Whiteflies will scatter and flee, and the pressure from the water stream will dislodge nymphs and eggs too.
If your tree is heavily infested, consider using insecticidal soap and targeting the undersides of the leaves. You can also opt for a homemade mixture of dish soap and water to scatter whiteflies. If all else fails, or you don’t have access to other solutions, you can use a handheld vacuum to suck them up.
How to prevent whiteflies
As a general rule, always inspect new plants you’re adding to your yard to be sure pests are hitching a ride on the new landscaping. Nonetheless, a few tips to prevent whitefly invasion include:
- Planning a habitat that attracts and keeps natural predators around. Ladybugs, green lacewing larvae, spiders, hummingbirds, and dragonflies all love to hunt whiteflies.
- Avoid using chemical insecticides for whiteflies because it won’t always work, and you’ll end up killing off the beneficial insects in your yard.
- Set out bright yellow index cards covered in petroleum jelly or a mixture of petroleum jelly and dish soap to monitor and catch whiteflies. The yellow color looks like new foliage to the whiteflies, and when they sit on it, they get stuck in the jelly and die. This works especially well if you are growing tomatoes, cabbage, or sweet potatoes.
- Try to mulch early in the season, especially around peppers and tomatoes, with an aluminum reflective mulch. Reflective mulch makes it hard for whiteflies to hunt their preferred host plants.
Scale insects
Scale insects are another common sap-sucking pest that stays on the inner part of your tree’s bark. They are from the subfamily sternorrhyncha and include a large number of hard- and soft-scale insects.
Scale insects have a hard shell that enables them to pierce twigs to suck sap. They can stunt growth in a healthy tree and might even be fatal if the tree isn’t treated timely. Scale insects leave behind a sticky excretion that forms a layer of sooty mold. Their favorite time to attack lilac, dogwood, ash, willow, and maple host trees is the early spring.
How to tell if you have scale insects
Scale insects are commonly found around twigs, tree branches, fruits, and leaves, and they munch on phloem with their sharp mouthparts. As they pierce or suck through the surface, they leave your tree with limp leaves and discoloration.
Signs of a scale insect infestation include premature leaf drops, chlorosis, or yellowing accompanied by branch dieback and restricted growth.
Look for scales along the central leaf veins, leaf backs, and stems. These insects also form colorful clumps from the sooty mold on twigs and leaves of your tree.
How to get rid of scale insects
The best time to treat infected trees is the last few weeks of winter. These insects can reduce your tree’s vigor, and cases of severe infestation may require the expertise of a professional arborist and chemical treatment. However, this might not be a great solution as harsh chemicals can also kill natural predators that feed on scale insects.
You can control an outbreak with a spray of soapy water, especially in the case of young scale insects. You can also use an old toothbrush dipped in soapy water to remove the old, adult scales. Dabbing individual insects with a cotton swab soaked in a neem-based solution or alcohol will also work for light infestation. Oil-based insecticides, horticultural oils, and fast-acting botanical insecticides have fewer harmful effects and will work in most cases.
How to prevent scale Insects
Some practices that can help keep scale insects away from your trees include:
- Encouraging the growth of beneficial insects like lacewing and ladybugs around the lawn, as they are the best natural predators of young pest larvae.
- Occasionally spray your plants with insecticides containing neem oil, especially before the onset of spring. It’s not toxic and keeps pests away.
- Scale insects tend to attack plants with a weak foundation. Hence, providing adequate nutrients and irrigation to the soil will keep it healthy and trees growing in it would be able to handle moisture fluctuations and pest attacks better.
Wood borers
Asian longhorn beetle
The Asian longhorn borer, or beetle, first appeared in the late 1990s in New York and has spread from there. These small pests can fly from one city to another in search of a new host. They lay eggs in the same trees from which they emerged, so it’s slightly easier to control an Asian longhorn outbreak.
These round-headed borers have antennas bigger than their bodies. Their host trees include populus, platanus, plane-tree, poplar, elm, willow, and salix.
How to tell if you have Asian longhorn beetles
A tree afflicted with Asian round-headed longhorn beetles will have dust-like frass or sweet sap excrement on the branches and trunk of the tree. Their larvae also have a round shape that leave an oval or round tunnel in the bark.
Other indications of an attack include chewed round depressions along the tree’s bark, unseasonal drooping and yellowing of leaves, and pencil-sized exit holes. Other than that, Asian longhorn beetles are large enough to be visible. They range from ¾ inches to 1 ½ inches long. You can spot them on outdoor furniture, walls, cars, pool filters, or sidewalks.
How to get rid of Asian longhorn beetles
There is not much you can do about Asian longhorn beetles other than simply take proactive measures to prevent their outbreak. The only way to get rid of them would be to destroy the infected tree altogether to contain the infestation. You will also have to remove all other trees that were potentially exposed to the infested tree.
How to prevent Asian longhorn beetles
These invasive insects are known to kill your trees from the inside out. Here’s what you can do to prevent them:
- Keep inspecting your tree bark and branches for any signs of sawdust buildup near the base, holes, or slow growth.
- Moving firewood can spread these pests. Thus, closely examine when you’re dealing with firewood around a healthy lawn.
Emerald ash borer
Emerald ash borer, or Agrilus planipennis, came to North America in the 1990s and targeted ash trees. A mature emerald ash borer has a striking metallic green color and a purple hidden abdomen under the forewings. They are no more than 4 mm wide and can reach about 15 mm in length. Ash borers fly in search of mates during June, July and August.
These pests kill millions of ash trees each year, but there is a high probability the infestation will go unnoticed for two or more years after these deadly borers enter your tree.
Emerald ash borers feed on vascular tissues present between the sapwood and tree bark. And since they stay in this spot for food, it interrupts the flow of water and nutrients through the tree causing slow degeneration.
How to tell if you have emerald ash borers
You can spot emerald ash borers from the S-shaped feeding galleries they create that have sawdust and frass packed inside. When the adult borers emerge out of the tree, you will see D-shaped holes in the bark. These holes are just ⅛ inches in diameter which are, again, very hard to locate.
Other symptoms include yellowing foliage. A split bark and lots of sawdust around the tree will confirm the presence of emerald ash borers. You will also start spotting adult green-colored beetles roaming around or woodpeckers coming to remove the bark to munch on larvae under it.
How to get rid of emerald ash borers
If you have detected an infestation in its early stages, chances are you can save your tree by controlling and killing off the active borers. Although they are difficult to treat, a few insecticides have proven successful at killing the pest in all stages of its life.
A common method to get rid of these borers is to drench the soil around an infected tree with diluted insecticide. The main ingredient in such insecticide is imidacloprid, which is approved for use by professionals and homeowners both. As the tree absorbs the insecticide, it kills the pest when they feed on the tree tissue laced with insecticide.
You can also inject an insecticide into the bark. Also effective are spray treatment with ingredients like carbaryl and acephate in the insecticide. If the infestation is severe – say 20 percent of the canopy has been destroyed – you will need to destroy the tree to limit its spread.
How to prevent emerald ash borers
Although it is hard to prevent an infestation at its initial stages, you can surely stop it from spreading to other trees. A few tips to keep them away include:
- Avoid moving firewood from other sites as it poses a high chance of spreading the pest.
- Burn down any remaining firewood from the last season before spring begins.
- If you’re buying a new ash tree from the nursery, inspect it thoroughly to make sure it’s not already infested.
- Be careful when using a string trimmer or mowing so you don’t wound the bark of your ash tree because the fresh trunk is always attractive for egg-laying borers.
- Stay away from tree wraps as they can delay proper bark hardening and encourage borer attacks.
Weevils
Weevils are a part of the big beetle family. They are tiny, practically invisible to the naked eye. Unlike other borers that make tunnels or galleries in the wood, weevils dig hollow cells or cavities underneath the tree’s bark. They target the bases or roots of woody trees and shrubs like azalea, strawberry, holly, grape, and rhododendron.
Weevils prefer moist, warm environments. They can lay eggs in rolled up, new leaves and can also invade your home looking for shelter and food. Some common weevil types include rose weevil, granary weevil, alfalfa weevil, black vine root weevil, and rice weevil.
How to tell if you have weevils
Two main signs point to the presence of weevils. First, the leaves on your tree will start appearing marginally notched or scalloped. A severe infestation from adult weevils can even completely consume the leaves and leave behind the main vein.
Second, you will notice stunted growth and yellowing leaves. The weevil larvae feed under the soil on the feeder roots and can cause more damage to the tree because it’s hard to diagnose.
How to get rid of weevils
The treatment plan for weevils largely depends on their stage of life. In case of heavy infestation, you can manually remove the adult large-sized weevils. You can wipe out root weevils with granular grub control if they are still at the larvae stage. Chemical insecticides will work in this stage only if the larvae are feeding actively.
You can also use beneficial nematodes. They are small round worms that are harmless to other beneficial insects, pets, wildlife, and humans. They selectively seek out adult as well as larval- stage weevils. Apply them from early spring till the fall for complete and effective control.
How to prevent weevils
A few tips to save your trees from weevil infestation include:
- Keep your garden neat. Weevils hide in compost, under mulch, weeds, or debris.
- Avoid excessive watering as weevils are attracted to water.
- Practice proper crop cultivation and rotation to get rid of any weevil larvae.
- Encourage a habitat for safe predators like woodpeckers, hedgehogs, frogs, praying mantises, and ladybugs.
- Chickens are natural predators of this pest; you can keep chickens to deter weevils.
Defoliators
Gypsy moth
Lymantria dispar, or gypsy moth, is the most notorious tree pest in the Eastern United States. A record 12.9 million acres of trees were defoliated by this pest in 1981. These leaf-miners are also called the spongy moth owing to their sponge-like egg mass.
Hungry gypsy moth larvae love to feed on hardwood trees, especially birch, oak, maple, and elm. Trees that suffer from repeated leaf removals usually become stressed and vulnerable to attack by moths. Once the gypsy moth has established itself in a location, it will have cycles of large outbreaks every 12 years.
These pests stay well-camouflaged and can easily get to your trees from new firewood or camping equipment. Common hosts include hawthorn, willow, birch, alder, apple, oak, and basswood trees.
How to tell if you have gypsy moths
You will notice defoliation mainly. It could be restricted to a few branches or spread to the entire tree. The gypsy moth can be identified at all four of its stages from distinct coloring.
It lays teardrop-shaped egg masses that are tan to yellowish and can contain up to 400 or 500 eggs at once. They might seem hairy and are usually 1 inch to 1 ½ inches in length. You can spot them on outdoor furniture, tree trunks, or home siding in the next larvae stage.
The moth grows up to 2 ¾ inches in length, and it develops a black or brown body with six pairs of red bumps at the back and five blue bumps at the front. Around the middle of summer, adult moths arrive. Males are brown and fly, while females are cream-colored, larger, and cannot fly.
How to get rid of gypsy moths
Gypsy moth outbreaks can last for one to three years. The best way to get rid of them is to kill them at the larval stage with pest spray oils or by simply scraping them off and killing them.
Burning or drowning them in kerosine will do the job. You can also kill these eggs by submerging them in soapy water for two days. Horticulture oil insect sprays in the fall and early springtime are also effective.
How to prevent gypsy moths
There are several things you can do to prevent moths:
- Wrap your trees in burlap to catch any eggs laid between the burlap flaps.
- Survey your property regularly in the fall for any egg masses.
- Keep your trees healthy and strong by taking care of the soil, water, and nutrients.
- Remove all the possible sites where egg-laying gypsy moths can hide. This includes piles of old wood, dead branches or debris, mulch, weed, and bark flaps.
- Encourage the natural enemies of these pests, like robins, starlings, chipmunks, squirrels, ants, and several species of spiders.
Spruce budworm
Spruce budworm is one of the most catastrophic forest pests. They multiply in large numbers and the larvae have the potential to defoliate an entire tree.
Adult budworms have a dull gray color with brown spots and bands around the body. The larvae are cylindrical and long, about 18 to 24 mm.
Their host trees include white spruce, black spruce, and balsam fir. The larvae usually hide in the crown’s interior during winter and emerge in May to feed on unopened buds, old needles, or male flowers. They turn into adults by early July.
How to tell if you have spruce budworm
Spruce budworms are messy eaters. They bite off needles around the base, cover them in a mass of silk and leave them hanging. They usually form a feeding tube by webbing two or three shoots together. You can spot masses of red-brown, dried needles hanging from branch ends when there’s a budworm infestation.
Other evidence of spruce budworm presence includes an abnormal spread of new twigs, bud destruction, and defoliation on new shoots. Defoliation usually begins at the current-year needles and top of the tree. In case of severe infestation, trees can become rust-colored because of the large number of silk-spun larvae and dried, hanging needles.
How to get rid of spruce budworm
One way to get rid of spruce budworm in its early stages is proper pruning. You can hand-pick or use a strong stream of water to dislodge larvae from small trees when the numbers are still low. But to substantially reduce a serious outbreak, you would need chemical insecticides.
Aerial sprays offer short-term protection, while bio-pesticides with active ingredients like Spinosad work great for this pest. Bacillus thuringiensis is a natural, soil-dwelling bacterium that is particularly effective for larvae elimination, thus great for the early stages of budworms’ life cycle.
You can also use concentrated sprays with azadirachtin, the main insecticidal ingredient in neem oil, to halt their growth at any stage. As a last resort, you must opt for the least-toxic botanical insecticides.
How to prevent spruce budworm
Here are a few practices for preventing this pest:
- Generally, spruce budworms are kept at bay by a combination of parasites, restricted food supplies, predators, and climate conditions.
- Improve tree health with good silvicultural practices. This includes promoting mixed-tree stands, thinning, watering, and fertilizing to contain the risk of infestations.
- A variety of birds, spiders, and several insects are important predators. Promoting a habitat for them could help you in discouraging budworms.
It’s always better to stay ahead of troublemaking pests as an oversight can result in serious damage to your trees and landscape elements. We went through the most common pests that damage trees in detail to help you combat them. And if you don’t like to get your hands on pests, you can always hire a Lawn Love pro to assist.
Main photo credit: Jimmy Chan | Pexels
