Know the enemy

Spring is just around the corner, and with it comes the threat of tree diseases, something your team may be ill-prepared for.

“Generally speaking, your diseases by and large are regional anomalies if you will,” says Nate Dodds, owner of Mauget Tree Injection in Arcadia, Calif.

The diseases may not necessarily be new, they’re just something you aren’t familiar with because they haven’t been as prominent in the past.

“There are a number of diseases that have been here a while that get worse when weather conditions change,” says Rob Gorden, director of urban forestry and business development with Arborjet in Woburn, Mass. “Some of these diseases are getting worse because temperatures and moisture levels are increasing in parts of the country.”
 

Recognize the threats.

Diseases tend to thrive in areas with higher moisture levels because it’s easier for their spores to travel from one leaf to the next. According to Gorden, Oak wilt is an issue all the way from Texas up to Michigan.

A fungal disease, it can be spread by insects and through underground roots from an infected tree to a healthy tree.

Jim Rollins, eastern sales representative for Mauget, says fire blight hit the Midwest hard last year. “It was mostly on pear trees,” he says. “I think it has something to do with the harsh winter we had last year, so we’ll probably be dealing with it next spring.”

He also says bacterial leaf scorch hit the Midwest, mostly on oak trees ranging from New Jersey to Milwaukee.

“Diplodia tip blight seems to be getting progressively worse each year,” he says. “Root rot seems like it comes and goes. I suspect it follows a heavy rain year when you have a lot of soil moisture. We’re coming off a rather dry year so it probably won’t be a problem.

“Many of these new pests coming into the country are actually insect vectored diseases, meaning the insects bring the disease as food,” Gorden says. “That’s going to become more and more of a problem in the U.S.”

Dodds says a variety of Fusariums, one of these insect vectored diseases, are becoming a concern in Florida. “Out here, we’ve got a Fusarium disease being spread by a relatively new insect,” he says. “The borer causes damage to the tree but the most devastating part of the infestation is that it deposits a few Fusarium spores within the tree and that Fusarium is a food source for the hatching larvae to feed on.”

Not only does it provide a food source for the insects, but the fungal disease is a vascular plugging disease that will kill the tree.

Dodds says another concerning one is the polyphagous shot hole borer in California.

“It can kill up to 200 different tree species in the California area and can reproduce on 20 of those,” he says. “It’s spreading. It started out around L.A. and has spread up to Pasadena and San Diego.” He says as of now, no one is certain how far it’s going to expand.
 

Start with a good defense.

Gorden says it’s important to remember that tree care is different than lawn care, especially when it comes to diseases.

“When something is wrong with the lawn, it’s really obvious really quickly,” he says. “Replacing lawns is much, much less expensive than a tree that suddenly dies on you. Tree problems tend to take a longer time. I hear from our clients that they don’t begin noticing calls come in from their customers until the tree is dire.”

The best form of treatment is to prevent them from happening in the first place, something easier said than done. “It’s hard to prevent (tree diseases) when the problems are moisture and spores,” Gorden says.

He says the best way to prevent diseases is to keep the trees as healthy as possible. “Just like in humans, plants are attacked by diseases more commonly when they’re under stress,” he says. “It has everything to do with your body being stressed out and being more susceptible. It’s that way with trees as well.”

“Generally your greatest chance of preventing a disease is to maintain a tree’s health in the first place,” Rollins says. He suggests a pruning schedule, adequate fertilizer, insect control, making sure the tree gets sufficient moisture (without getting too much) and presenting a preventative fungicide or antibiotic program.
 

Find the right treatment.

So you did everything you could and a customer’s tree got infected anyway. Never fear, there are treatment options available to help, although when it comes to treating the diseases, the options can vary as much as the diseases themselves.

Because of this, it’s important to properly diagnose the problem and be well equipped with the knowledge of what effect the disease will have on the tree. “Treating for fungal diseases is probably a much more difficult part of a contractor’s service because it’s considerably much more difficult to diagnose and read the symptoms of a tree,” Dodds says. “It requires a lot more study on the contractor’s part and gaining of knowledge to know what he’s got.”

Dodds says your best bet is to consult with your local university extension to get up to speed on what’s active in your area. The extension might also have suggestions on what products are recommended for treatment.

If a university extension isn’t available in your area, go to a local grower. They’ll know the predominant diseases, the symptoms and how to recognize them.

“There are a lot of good resources available to get them started,” Rollins says. “I would encourage landscape contractors and others in the business to consider getting into the tree care health part because it’s a service a lot of their clients can benefit from.”

“For most (diseases,) the infection point occurs in the fall or early spring when the trees are blossoming or coming out of dormancy,” Dodds says. “The symptoms do not manifest themselves until mid- to late summer.”

There are two treatment options that can help control tree diseases: trunk injection and foliar applications. When you start dealing with larger trees, particularly in an urban area, Rollins suggests using trunk injection. “It’s more systemic in nature, and affects the vascular parts of the tree,” he says.

He says it’s a good idea to treat these before the disease can be heavily established and cause damage.

“It’s not a bad idea to provide an application the second or third year after you’ve identified a disease,” he says. “That way you’ve completely eradicated the disease and reduced the possibility that it comes back immediately.” Treatments for tree diseases don’t require specific certifications, other than what your pesticide applicator should have already.

“Generally they’re going to be administered through a trunk injection application,” Dodds says. “Thereby you have very little environmental exposure; they’re safe chemicals to use.”

However, every state has its own licensing procedure to apply pesticides in the commercial form and you must have your state licensing in order to be able to buy and sell these products to your clients.

“It may be the basic license required,” Gorden says. “However, the good news is most landscape contractors who are already doing lawn care may already have the license for tree and shrub care.”