I got a call from Mr. Davis who owns a large manufacturing plant in Grand Rapids, Michigan. He said his flowering crab trees were losing leaves.
The call came in July, which is prime season for apple scab. Apple scab is far and away the most common disease to afflict the apple (Malus) genus, which includes flowering crabs. The scab fungus Venturia inaequalis causes spots to form on the foliage in June. By mid-summer, the spots coalesce and turn the leaves brown. By Labor Day, trees are often bare.
Mr. Davis said that his landscape maintenance company told him his trees suffered from apple scab and not to worry. “The disease isn’t fatal and, being July, it’s too late to do anything about it until next spring. They’ll be fine,” they told him. “Come next April, you’ll never know there was a problem.”
The maintenance company was right. If it was apple scab, which seemed likely, then the trees would be fine. They also were right about the problem needing to be treated in the spring. Control consists of applying fungicide sprays in April and May. The sprays must be done preventively to be effective.
Read more: Understanding Foliage Diseases
Flowering crabs are one of the most widely planted ornamental trees in North America, and for good reason. They’re extremely hardy. In Michigan, flowering crabs bloom profusely from late April until the end of May. Both the flowers and the tiny apples come in a wide assortment of colors. The trees are so laden with blossoms in May that they look like a pink, violet or rose cloud. When the sun rises or sets behind a tree in full bloom, the crown glows.
For arborists, flowering crab trees are so prevalent that dealing with apple scab is practically lesson one of chapter one. I knew the people taking care of Mr. Davis’ trees. “They’re good people,” I told him. “I rarely hear complaints. If you don’t mind me asking, why are you calling me?”
“Because they won’t come out and look at them,” he said. “They told me that apple scab is rampant this year, that it’s been a very wet spring. They say it aggravates the problem. They told me the falling leaves are a classic symptom. They’re getting lots of calls.”
“They never actually came out to look at your trees?” I asked.
“No, and I’m worried,” he said. “They’re beauties. They’ve got to be at least 50 years old. When they’re in bloom, they stop traffic. People will get out of their cars and take pictures.”
The next day I went to see his trees and could understand why he was so protective of them. There must have been 60 trees. They looked well cared for, nicely trimmed, the mulch beds edged. But they certainly looked to have apple scab. Even from the street, I could see the foliage was spotty and turning yellow. Beneath each one was a growing pile of mottled leaves.
Read more: How To Determine Tree Diseases
I parked in the lot and proceeded to walk through the grove, examining each one, occasionally stopping to look at individual leaves through a magnifying glass. Every tree was the same variety and about the same age. There are hundreds of varieties of flowering crabs, but his trees were all one particular species called Royalty crabs, which is one of the older varieties. Judging by their age, it appeared that the grove was planted when the facility was built in 1961. (The date the business was founded was imprinted on a brick by the door.)
The ground squished under my feet as I walked, evidence that Mr. Davis watered on a regular basis. The grass was a deep green color. The trunks and limbs of the trees were stained an iron color from the iron-rich well water the sprinkler system used. All of that water splashing the foliage would exasperate a fungal infection like scab.
As I checked the last few trees, something caught my eye. On the last two, and only those two, I noticed a few branches were wilting. All of the leaves on six or seven branches of the last two trees were completely brown. The branch-tips looked scorched and curled over, resembling a shepherd’s crook. Apple scab may cause trees to look sickly, but it doesn’t kill whole limbs. Those two trees had fire blight.
Fire blight is the scourge of the apple industry. Apple growers are ruthless when dealing with the disease. They should be. No spray or trunk injection stops it. Fire blight is a bacterial infection.
Fungicides are useless against bacterial diseases, and no effective antibiotics for trees have been discovered. There are a few experimental products, but none have proved terribly successful. The best remedy for fire blight, if it can be called such, is removal. Growers cut down the trees and burn them. If the disease goes unchecked, fire blight can wipe out an entire orchard.
Read more: Fire Blight: Still an Orchard’s Enemy from Growing Magazine
I could understand why the maintenance company skipped the site visit. It’s summer. They’re busy. When there’s a backlog of 30 stops to make, I’m tempted to diagnose problems over the phone, too. Ninety percent of the time, maybe even 99 percent in the case of apple scab, the maintenance company’s reply to Mr. Davis would have been correct.
I went inside the facility and explained the situation to Mr. Davis. I showed him pictures of the two diseases from reference books I carry with me in the truck. I pointed out how the two diseases differ.
He gave me approval to remove the two infected trees. “And, while you’re at it,” he said, “figure on spraying the rest of the trees next spring for apple scab.”
Read more: Controlling Fire Blight from Growing Magazine
One of the first lessons I was taught when I started working in the tree care business was, “You must go see the tree.” One of my early mentors told me you can’t properly diagnose a problem unless you see all of a tree’s parts, investigate the site where it grows and learn about what care, if any, the tree has received — none of which can be properly described over the phone or from seeing a couple of photos.
“Always go see the tree.”
When I began my career, Bob Kelly, 20 years my senior, had already been in the tree business for 30 years. He told me every tree species has one, or maybe two, primary nemesis. If you know those one or two pests, and which tree they prefer, you’ll be able to diagnose 90 percent of any tree’s problems. Emerald ash borers in ash trees, locust plantbugs for locusts, and willow leaf beetles in willows are pests so common to those species that the insects are named after them.
Bob would then note, “An arborist, however, is someone who can identify the other 10 percent of the problems. And that, my boy, takes a long time to learn.”
He’d add as an aside with a twinkle in his eye, “By the way, people rarely call arborists to diagnose the 90 percent caused problems. It’s the 10 percent they call you about.”
As Bob so aptly pointed out, the trick to becoming a good arborist is to become familiar with the long list of obscure insects, diseases and cultural problems that damage not only the common trees, but also the lesser ones, too. Problems in the field rarely look like they do in textbooks. It takes a great deal of field experience to run across all of those weird, oddball problems which, fortunately, seldom raise their ugly heads.
Bob had no forestry or biology degree. He went to school at what he called “The School of Hard Knocks.” Bob served in the Army in the 1950s and did a stint in Panama. When Bob and his wife, Trudy, returned to Grand Rapids after his tour, Bob got a job at his brother-in-law’s tree service. Bob began his career in the 1950s, during the heyday of the Dutch elm disease epidemic. He was a big help in teaching me how to approach the emerald ash borer crisis when it arrived.
Bob had several other tenets by which he worked. Many of them were humorous in nature. A couple of his favorites were, “If it ain’t got no bark, it ain’t got no spark.” Or, “How well would you breathe if I buried you in 12 inches of mulch?”
But lesson one of chapter one in Bob’s Tree Care Book was, “Always go see the tree.”
Fortunately for Mr. Davis that day, it was a lesson I took to heart.