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How to Manage Tree and Shrub Diseases in Winter

Winter tree care here in Idaho isn’t usually a big deal. Mostly, you can spend the winter gazing out at the lovely snow-laden branches, watching the antics of the occasional squirrel, and wondering if you should maybe hang a bird feeder out there.

So winter is a slow time for winter tree diseases in Idaho, but we have noticed more fungus and diseases in general lately than in the past, and treat them with fungicides as needed. 

Let’s take a look at a few common Idaho tree and shrub diseases, and what to do about them:

Marssonina Leaf Spot

Common on aspen trees, this fungal disease affects aspen, poplar, and cottonwood trees.

leaf spot
You’ll typically notice brown spots with yellow halos on leaves. Many of these spots eventually merge together, creating large brown blotches. Leaves may drop prematurely. 

The disease doesn't typically kill trees, but stresses them and may weaken them over time.

Rhizosphaera Needle Cast 

This fungal disease of spruce trees causes needles to turn brown and fall off. 

Trees stressed from drought, poor planting practices, or other factors are more likely to suffer from it.

Proper planting and air flow is your best defense. (More on this, and other winter tree care, in a bit.)

Powdery Mildew

This fungal disease looks just like it sounds. White to gray powdery spots, blotches or felt-like mats form on leaves, stems and buds of infected plants.

Powdery Mildew
Although any tree can get this common disease, the ones that are most commonly affected are oak, maple, dogwood, magnolia, catalpa, and crabapple.

Fire Blight

Fire blight is a common and very destructive bacterial disease of apple and pear trees. 

Caused by a bacteria, the disease can kill blossoms, fruit, shoots, twigs, branches and entire trees. 

Fire blight bacteria overwinter as cankers in the tree’s tissue. The infection is spread once the trees bloom and bacteria are carried from the cankers to open flowers by splashing rain, pollinating insects. or during pruning.

fire blight

While spraying fungicides can help, Lawn Buddies technicians often treat this with tree injections, an important part of tree and shrub care in Idaho Falls and Boise, ID. 

Tree injections are like shots for your trees. They treat diseases and insects by delivering “medicine” directly into the tree trunk, which is quickly taken up by the vascular system and distributed throughout the tree.

This direct treatment works faster and is more effective than spray treatments.

How to Prevent Tree and Shrub Diseases in Winter 

Nobody wants to see big brown spots on their aspen leaves, watch diseased needles fall from their spruce, or lose a beloved apple tree. 

While fungicides and tree injections can treat diseases, preventing them in the first place is even better, right?

Here’s how:

Proper Planting

Pick the right tree or shrub for the area, and plant it at the proper depth.

Healthy trees and shrubs
Planting trees too deep is a common mistake. It can lead to root rot, thinning canopy, cankers, and all sorts of other problems. 

Even the best Idaho tree and shrub health care can’t make up for a poorly planted tree.

Winter Tree Care: Proper Pruning 

Pruning is a huge tool for disease management. 

Winter is the best time for pruning trees and shrubs. 

Horticulture Tools on wood floor
This time of year, when your trees and shrubs are dormant, you’ll do less damage when you prune, shape and thin your deciduous plants than if you tackle it in their prime growing months.

Those fresh pruning cuts you make heal faster during the dormant season — and are less likely to attract insects, which can carry diseases. 

When pruning out diseased areas, be sure to disinfect your pruners in-between each cut. Otherwise, you’ll help spread the disease.

Apply Fungicides 

Applying fungicides in late winter or early spring before the tree or shrub starts growing can help prevent diseases. 

plant health care technician sprays trees
But this is a job for professionals in tree and shrub care in Idaho Falls and Boise, ID, because the exact treatment differs depending on the type of tree or shrub and the disease you’re trying to prevent.

Are Your Trees and Shrubs Ready for a New Best Friend?

Tree and shrub diseases in winter aren’t a huge problem in Idaho. 

But don’t forget about tree and shrub health during the other three seasons. 

A good plant health care program is your plants’ best friend, offering food and fixes for every pesky problem, from disease control to tree and shrub fertilization to tree injections to boost your trees’ health. 

Plant Health Care Services can be added to our Complete Health Care Program in Idaho Falls or Boise.

The first step is to sign up for our 6-step complete lawn care program. 

You’ll be glad you did. 

Choose an Idaho Falls or Boise professional lawn care service that makes it easy, bundling your yard’s most-needed treatments into one convenient, no-fuss plan.

Fertilizing, weed control, grub control. Done.

We’ve got your back. 

Got a few minutes? That’s all you need to get started. You can simply:
Fill out the form on this page.
Call us at (208) 656-9131.
Or read more about our services.

Then kick back and relax in your healthy, thriving yard.

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Image Source: Leaf Spot, Powdery Mildew, Fire Blight


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