You Might Have Phytophthora Root Rot if Your Trees Show Early Fall Color in the Middle of Summer

If one of your trees started showing fall color in the middle of summer, or you've noticed dark, oozing spots near the base of the trunk, it's worth a closer look. 

What Is Phytophthora Root Rot?

Phytophthora root rot is a major tree health issue in our area, especially during wet years and wet springs like we have had here in central Missouri. 

It's a soil-borne pathogen that attacks a tree from the roots up. That's what makes it different from the leaf-feeding pests you can spot at a glance, like Japanese beetles. With root rot, the damage starts underground, so by the time the tree looks stressed above ground, the problem has usually been building for a while.

Why Phytophthora Root Rot is So Damaging

Root rot damages the fine absorbing roots a tree depends on. Those fine roots are how a tree pulls in water and nutrients, so when they're compromised, the whole tree starts to run short, no matter how much water is sitting in the soil around it.

That's also why a struggling root system tends to show up as general decline in the canopy. A weakened tree is more susceptible overall, which is why tree health and prevention is best. A tree already dealing with heat, drought, or compacted soil has less in reserve to fight off a root infection, and the two problems can feed each other.

What Does Phytophthora Root Rot Look Like?

One of the first visible signs we often look for is black staining, dark oozing, or weeping spots on the lower trunk or around the root flare. This can indicate a bleeding canker or crown/root infection. Another warning sign, especially on maples, is early fall color showing up in mid to late summer, particularly when it shows up mainly on one side of the tree instead of evenly throughout the canopy.

That one-sided pattern is a key clue. For root rot, you'll often see early color change on one side of the tree, or general decline, rather than the even, whole-canopy color you'd expect in a healthy fall. If part of your tree is turning while the rest stays green, and it's still summer, that's worth having looked at.

What Causes It, and Why Wet Conditions Matter

Phytophthora thrives where the soil stays wet. Wet years, wet springs, and landscapes where irrigation or runoff keeps the ground around a tree consistently soggy all create the conditions it needs to take hold. In many cases it's tied to how a property drains or how it's watered, not just to the weather.

This is important for homeowners to remember: when a tree looks stressed, water isn't always the answer, so it's worth being careful about defaulting to watering a struggling tree more. If the roots are already sitting in wet soil, more water can make a root problem worse rather than better. When you're not sure what's driving the stress, that's a good time to have a professional take a look before changing anything.

How Ratliff Tree Approaches Treatment

For best results, we often recommend deep root feeding with phosphite added.  Our deep root feeding is a root- and soil-focused treatment mixed specifically for trees and injected below most grass roots throughout the tree's active root zone. This helps address compaction, improves movement of air, water, and nutrients, and places the treatment where the tree can use it while reducing waste and runoff. The treatment supports root growth, soil biology, nutrient availability, vigor, and stress tolerance. We also include phosphite to support natural disease resistance and provide protection against Phytophthora and other root rot issues.

Deep root feeding is a great yearly maintenance treatment for young, mature, and advanced-age trees. Late summer and fall are a very beneficial time for treatment, although it can be performed throughout the growing season with our approach.

For trees under added stress, a growth regulator treatment can support the effort as well. It helps redirect the tree's energy from excessive top growth into roots, storage, and defense, which improves root development and makes the tree more resilient. It's also a good option for trees facing root disturbance, such as before or after nearby construction.

When Phytophthora is suspected or confirmed, Ratliff Tree develops a treatment plan based on the tree’s condition, the severity of symptoms, and contributing site factors such as excess moisture, poor drainage, and soil compaction.

The plan may include a specialized root-zone feeding with antifungal and water-mold protection. This treatment is designed to help protect against Phytophthora and related root rot issues while supporting root recovery, nutrient uptake, soil health, stress tolerance, and the tree’s overall natural resistance to disease.

Because Phytophthora damages the fine roots a tree relies on to absorb water and nutrients, treatment focuses on both managing the disease pressure and improving the tree’s ability to recover. Late summer and fall can be especially beneficial times for treatment, although our approach allows us to treat during much of the growing season.

For trees experiencing additional stress, such as construction damage, root disturbance, or severe compaction, other supportive treatments may be added to the plan to encourage root development, improve stored energy reserves, and strengthen the tree’s natural defenses.

Can You Stop Root Rot Before It Starts?

A lot of root rot risk comes down to site conditions, and that's where prevention pays off. Choosing the right tree for the right place, keeping soil from staying waterlogged, and not overwatering all reduce the pressure a tree is under. Because phosphite treatments strengthen a tree's natural disease defenses, they're valuable as a preventative step too, not only once a problem shows up.

Healthy roots are the foundation of a healthier, more resilient tree. It is much easier to keep a healthy tree healthy than to bring one back after serious decline has started, and the benefits of regular supportive care build over time. 

Contact Ratliff Tree for a Tree Health Consultation

Root rot is easier to manage when it's caught early, while there are still healthy roots to build on, so if you're seeing early fall color, one-sided decline, or dark spots near the base of a tree, it's worth having it evaluated.

You may already have someone taking care of your lawn, but do you have a tree expert taking care of your trees? Ratliff Tree's Plant Health Care team, led by a certified master arborist, can evaluate your property, confirm what's going on, and recommend a treatment plan that fits your trees. Request a property consultation or call us at (573) 446-2266.