What Bugs Are Eating My Trees? The 9 Worst Tree Insects in Idaho


When bugs show up in scary movies, they’re usually giant, like those creepy spiders in Harry Potter. Or fierce, like that queen of the monsters, Mothra.

They’re not usually eating trees.

But tree-eating bugs can be a real nightmare, sucking the life from your trees, devouring the leaves, and causing entire trees to die.

Are bugs eating your trees? You might not even realize it, until it’s too late.

If you’ve ever stood on your patio shouting, “What’s eating my trees?!!!” we have the answers.

The Worst Tree Insects in Idaho


1. Cottony Maple Scale

This pest is so common in Idaho, “I could treat just this all day long,” says Lawn Buddies Division Manager Dillon Beardall.

Blame it on the popularity of the Autumn Blaze maple and its spectacular orange-red leaves. Nurseries sell them like crazy. People love them.

So does cottony maple scale.

Cottony Maple Scale on branches

Their white, cottony egg masses usually contain 1,000-1,500 eggs that hatch into crawlers that suck the sap from tree cells, then move on to munch the leaves.

Severely infested trees look like they’re covered with a string of popcorn. Twigs and branches die. An infestation can kill the tree.

2. Pine Scale

Don’t think you have pine scale? Think again, Beardall says — 99 percent of pine trees in Idaho have pine scale.

You just don’t notice it. (Don’t feel bad — most people don’t spend hours peering at their pine trees looking for pine scale.)Pine Scale tree insect

Pine scale looks like whitish scabs on the needles of your pine tree. But these “scabs” are actually armor that covers the insect and protects it over winter.

Meanwhile, after these pine-loving pests have happily feasted for two or three years, sucking the juice from the needles, you’ll notice your pine trees turning yellow, then brown.

3. White Pine Weevil

How do you know if this Idaho tree insect has struck?

Look for brown, wilted main shoots, called “terminal leaders” with the tips curved into a hooked "shepherd’s crook."

White Pine Weevils

White pine weevils lay their eggs in the branches in the spring and the hatched beetles start feeding on them, cutting off water flow.

Soon, the tops of your pines will turn brown.

4. Tree Aphids

“Everybody has aphids,” Beardall says. Aphids are the most common insects found on trees, shrubs, and garden plants.

Tree Aphids

These tree-eating bugs feed by sucking sap. When a whole bunch of them gather to feast on your trees, like a bountiful bug buffet, their feeding can cause wilting and sometimes even dieback of shoots and buds.

5. Bronze Birch Borer

This coppery wood-boring beetle does the most damage as larvae. Unseen, it feeds on the vascular tissue under the bark.

It typically attacks trees that are already stressed or in decline, so here’s a plug for good tree health care.

Bronze Birch Borer

A birch infested with bronze birch borer will start showing dieback in the crown. As the infestation continues, you’ll see D-shaped, rust-stained exit holes in the trunk.

The worst-case scenario? You lose your beautiful birch.

6. Ash Borer

While the famous emerald ash borer gets all the attention lately, regular old ash borers are out there quietly feasting, out of the spotlight.

Emerald Ash Borer

Native ash borers typically attack stressed trees, boring deep into the tree, unlike the emerald ash borer, which attacks the tissue just beneath the bark.

Are these bugs eating your trees? Look for a mixture of sawdust and borer poop accumulating in the crevices of bark, on branches, and on the ground.

7. Spruce Gall Adelgid

With their sucking mouth parts, these Idaho tree bugs feed on plant juices, creating an irritation that causes plant tissue to develop into cone-like galls.

Spruce Gall Adelgid on branch

These galls disfigure your spruce trees, weaken them, and make them vulnerable to attack by other pests.

8. Spider Mites

These tiny critters are part spider, part tick, part ick.

They hang out underneath leaves and are itty bitty, so you don’t even know they’re there. Until they start leaving clues: watch for leaf drop or yellow, orange, brown, or gray spots on your tree’s leaves.

Look closer, and you’ll see fine webbing under and around the leaves.
Spider Mites
Spider mites attack plants suffering from drought, so be on alert during the hottest, driest parts of the year.

Better yet, keep your trees well watered.

9. Apple Codling Moth

Like its name suggests, this pest is all about apple trees.

Damage is done by the larvae, cream-colored caterpillars that tunnel into the fruit and produce “wormy” apples.

If you think that’s gross, it gets worse. They leave crumbly golden poop behind by the hole where they exit the apples.

Apple Codling Moth

Kind of makes you want to switch to grapes.

Beardall suggests using dormant oil on apple trees to deter the pests, which won’t affect the fruit.

How to Keep Bugs From Eating Your Trees

So, that’s quite a lineup of tree insects in Idaho, munching away.

Your best defense is a one-two punch of systemic injections plus foliar treatments, Beardall says.

Systemic insecticides injected into your trees in the spring and fall treats them from within, while spray treatments three times a year zap any bugs crawling on your trees. The foliage spray has a residual effect, too, lasting for 30 days to deter any hungry invaders.

“It’s so much easier to prevent bugs than to treat them after they show up,” Beardall says.

Are Your Trees Ready for a New Best Friend?

Ready to rescue your precious trees from villainous hungry bugs?

Tree bug treatments are available for our Idaho Falls and Boise customers who use our full-service lawn care program.

That gives you extra peace of mind — choose an Idaho Falls or Boise professional lawn care service that bundles your yard’s most-needed treatments into one convenient, no-fuss plan, plus know your valuable trees are protected from damaging bugs.

Fertilizing, weed control, grub control. Done. Tree protection. Double done.

We’ve got your back.

Got a few minutes? That’s all you need to get started.

Fill out the form on this page.
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Image Sources: Cottony Maple Scale, Pine Scale, White Pine Weevil, Tree Aphids, Bronze Birch Borer, Ash Borer, Spruce Gall Adelgid, Spider Mites, Apple Codling Moth

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