Drought conditions and recent rains in Gillette bring rise in tree disease


GILLETTE — R.J. Ellison sized up the gash broken into the aspen tree rooted in the mulch bed before him.

Several injectable vial-like containers of green liquid spilled out of his tool bag laid on the fertilizer near the tree’s base.

After measuring the diameter of each of the three narrow, divergent trunks, Ellison removed a drill and punched a shallow hole into the tree, low to the ground. Lining up the tip of the fungicide and nutrient solution into the opening, he tapped the small bottle in, breaking through the thin bark and letting the vascular system begin absorbing the liquid.

“The process starts instantly, that it’s trying to seal this wound,” said Ellison, a certified arborist and Wyoming Lawn Pro employee.

Each trunk would get two small drill holes and each hole would get one dose of the nutrient mix, aimed toward fighting back the Cystospora canker plaguing that aspen and other trees in Campbell County this year.

Although the fungicide and nutrient treatment may help, there is no cure for the tree disease affecting trees in the area this season.

The drought conditions of last summer helped grow the disease and the wet months of this spring helped spread it to trees throughout Gillette, said Wendy Clements, city arborist.

“It’s showing quite significantly through town, in not just city trees, but I’m seeing homeowner trees be affected by that as well,” she said.

Cystopora canker is common among spruce trees. When it takes hold, the trees turn from a yellowish green to a purplish brown, Clements said. Branches may lose all of their needles and begin turning the tree misshapen.

But through variants, the ailment can affect other trees besides spruces, such as the aspen Ellison treated. The disease begins when a fungus infects a tree stressed by weather conditions, insects feeding on it or other “mechanical” damage caused by animals, people, or lawn trimmers.

It doesn’t typically kill trees, but it hurts and deforms them.

It’s also incurable, although nutrient treatments can help the tree defend itself and neutralize the spread of the disease.

But before the right treatment can be prescribed, a diagnosis is required.

“It’s like detective work,” Ellison said. “You’re trying to pull clues out of the homeowner.”

Not all homeowners know how old the trees are, what the soil is like or when the trees were first planted. Ellison theorized that the aspen tree he treated that day had been cracked open by a deer at some point.

From there, the pathogen existing on the tree seeped inside, similar to germs entering the body and testing its immune system.

“The pathogen is always on this tree,” Ellison said. “With the drought — this pathogen likes the heat. Then with this wet spring, it absorbs moisture and it starts to spread.”

The fungal pathogen rests in wait, present on the tree surface until an opening in the exterior allows it to enter the tree and circulate throughout its vascular system.

“Almost all diseases and pests are that way,” Clements said. “To where they’re able to move in and attack when the tree is stressed and by the time you start seeing the symptoms of it, it often is too late.”

The “too late” time is now, as the disease grew during the months of extreme drought last summer and spread throughout the rainy spring.

Headed into the rainy Memorial Day weekend, Gillette had received 4.68 inches of precipitation since April 22. Prior to the breakthrough of rain toward the end of April, Gillette had only 1.24 inches of precipitation in 2022 and was enduring its third-driest start to the year, according to the National Weather Service office in Rapid City, South Dakota.

“We have these cycles where we get a few years of hot, dry weather, followed by a few years of wet weather, that’s where we notice it,” Clements said.

She remembered a similar uptick in Gillette of Cystospora canker, as well as Rhizosphaera, a fungal disease found in spruce trees — when a stretch of heavy rain followed an extended drought cycle almost 10 years ago.

“I think they’re both making a comeback,” Clements said of the two diseases.

Rhizosphaera is technically curable, but its treatment window is short, specific and has a low probability of success.

“You can go out and spend a lot of money on a product and if you’re not using it correctly at the right timing, you’re just throwing money into the wind,” Clements said. “Once that damage is done, that damage will always be there.”

Limited treatment

Although the treatment options are limited, there are preventative measures and management practices to build the defenses of those trees against infection.

“If you’re not trying to get on top of that and manage it a little bit, you may open up your trees to be susceptible to another pest or disease,” Clements said.

The protective measures are fairly simple. Clements said it’s often a matter of two things: watering and fertilizing.

Even with the spring rains Gillette received this year, Clements said it’s important to continue watering healthy trees even when they may not appear to need it. Diseases can set in when the tree looks healthy, and be too progressed to treat by the time the symptoms show.

Much of Campbell County has poor soil for growing trees, which is why proper fertilizing is so important too, Clements said.

“Sometimes our soils are so poor that they have the nutrients, but they’re so bound up, they’re not available for uptake,” she added.

That’s why Clements said she always recommends home and tree owners consult with a certified arborist before seeking treatments that can be pricey and at times ineffective.

In part, seeing the costs of the lawn care industry up close is what Ellison said moved him to get his arborist certification.

“The whole industry is kind of like a pharmaceutical company … that’s why it was designed to be so lucrative, it was supposed to come with some knowledge,” Ellison said.

Anyone can show up and spray chemicals or learn to identify spider mites. But it takes a more trained eye to know which chemicals may or may not help and how to use them, he said. It takes experience to know which kind of mite it is, and how to ensure those pests don’t return again and further damage the tree.

There may not be a cure for the tree diseases that have become more prevalent in Gillette this year, but that doesn’t mean they can’t be helped.

“Trees are resilient,” Ellison said. “There’s laws and rules, but there’s no absolutes.”

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