How to Prevent Fire Blight in Colorado: Tree Care and Fertilization

Fire blight is a major problem for trees in Colorado, specifically the Denver metro area. Fire blight can be prevented by taking care of your tree and fertilizing it properly. This blog post will discuss how to prevent fire blight in Colorado as well as how to take care of your tree during the winter and spring seasons.

What Is Fire Blight?

Fire Blight, also called Erwinia amylovora, is a bacterial disease that infects many types of fruit trees and ornamentals. It can cause significant damage to the bark, flowers, leaves, and twigs of susceptible plants. The bacteria produce an enzyme that breaks down plant cell walls causing the tissue to ooze or weep. This oozing sap attracts insects like bees who then spread the pathogen further through their feeding activities. 

Fire blight strikes most frequently in wet weather conditions between mid-April and late June when air temperatures are cool but soil moisture remains high for long periods of time as well as during fall months when storms bring rain from humid air masses from the Gulf Coast. 

The best way to prevent fire blight is through proper care of trees throughout winter and early spring. This includes:

  • winter tree trimming
  • winter watering
  • spring fertilization

Don’t sit on the sidelines and let your trees fall victim to this destructive disease. Follow these tips to take proactive action now and keep your trees and plants healthy throughout 2022.

Winter Tree Trimming

Winter tree trimming is a necessary practice to carry out in preparation for the upcoming cold months. This entails removing dead, diseased, and damaged branches from trees before they can risk falling during winter storms or becoming infected with fire blight bacteria (Erwinia amylovora).

For this step of how to prevent fire blight in Colorado, you will start by inspecting the trees on your property for signs of damage or infestation. A common issue seen during winter tree trimming is how to prevent fire blight from bird cherry-oat aphids, woolly adelgid, and twig girdlers which can all cause serious harm to trees by weakening the structure through their presence.

How do you know if a tree needs trimming? Here are a few key things to look for:

  • Hollowed and Cavities: Trees may decay from the inside until they are totally hollowed out if they are injured or destroyed.
  • Sapwood Damage: Under the bark around the tree lies an important protective shell of live sapwood. When damaged it will lead to exposed soft, discolored, decaying heartwood underneath.
  • Dead, Broken, and Hanging Branches
  • Mushrooms: Advanced decay has already begun whenever mushrooms (i.e. fungal fruiting bodies) spring from a tree’s roots or stems.
  • Cracks: Fresh cracks in a stem or branch are often a sign of a bigger problem.
  • Excessive Lean: Trees that are obviously leaning, or increasing in lean, or have soil heaving up around the roots may be compromised.

A thorough winter tree inspection can readily identify and inventory potential problems and hazards. Not confident in your own ability to spot these red flags? Contact one of our expert arborists to schedule an inspection today!

Once you establish which trees need trimming, it’s time to get down to work. Is it possible to DIY your winter tree trimming? Maybe, but most homeowners are not equipped to do a high-quality job. Here are three reasons why tree trimming is best left to the professionals:

  1. First, the necessary equipment is expensive, and homeowners may not be able to afford it. If they buy the tools anyway in order to do the job themselves, how will they store them? Most homeowners don’t have space for a large collection of power saws, ladders, and other tree care equipment.
  2. Second, tree trimming is inherently dangerous.  If a homeowner is not accustomed to working on ladders, how will they safely trim branches up in the air? What if they accidentally fall and hurt themselves or others nearby when using power saws required for tree pruning work? Not to mention the danger of nearby powerlines!
  3. Third, a good arborist will be bonded and insured, in addition to having training and years of experience. A professional tree trimming company will also have a list of references. Ask how many times the contractor has been called to address fire blight problems at nearby homes during recent winters, and how much those services cost homeowners.

Don’t give your trees a hack job in an attempt to save a buck, that always backfires! Instead, contact our expert team who can guarantee a quality job well-done. Your trees will look and feel amazing afterward.

To recap, winter tree trimming is considered preventative care because it removes dead or diseased branches before fire blight can take hold and spread. Winter is also the best time to fertilize your trees, as the soil moisture levels are still high and there isn’t the added stress of summer heat. Now we’ll go into more detail about when, how, and why fertilizing should be a priority.


What is tree fertilization and why do my trees need it? Fertilization is a process in which nutrients are added to the soil. The tree absorbs these nutrients through its roots, and it uses them for growth throughout the year. Fertilizing can significantly improve how well your trees grow (healthier leaves, more flowers) as well as how quickly they recover from stresses such as fire blight infection.

Fertilizing in spring helps promote new growth that will be more resilient to disease later in the season.  It is best to fertilize in the spring, as this gives your trees time to absorb all of their nutrients. 

Fertilizing your trees is like giving them vitamin supplements to stay healthy. But what nutrients should you look for in a fertilizer? According to Colorado State University, nutrient requirements for plants and trees can vary considerably. In general, nitrogen promotes leafy top growth. Phosphorus is needed for good root development. Potassium is necessary for winter hardiness, disease resistance, and general plant health. Our experienced arborists take a careful approach and use only the best fertilizing methods and practices.

One of the most popular fertilization techniques among other companies is tree spikes. Our experience and education continue proving that tree spike fertilizers are some of the least effective and even dangerous fertilization methods. We do not use tree spike fertilizers for three solid reasons:

  1. Tree spikes are too shallow – they don’t get past grassroots, rocks, and other debris near the surface. Your tree’s roots are often much deeper than the depth of a simple tree spike.
  2. Too small of a treatment area – Tree spikes only fertilize a singular spot and rarely treat more than the immediate area.
  3. Not environmentally friendly – A vast majority of tree spikes are still made out of plastic (not environmentally friendly!)

Well fertilized trees grow stronger and healthier, which makes them able to fight off fire blight when the threat comes near. When fertilization is used in conjunction with regular winter watering and strategic winter tree trimming, your trees will be thriving come spring and summer. 

Ready to get started with preventative tree care for your landscape? Call us today for your free consultation!