What is actually wrong with your tree

Dutch elm disease

Ophiostoma novo-ulmi

The fungus that removed American elm from Kansas streets in the middle of the last century, and it has not gone away. It is carried by bark beetles and travels between neighbouring elms through grafted roots, and the useful Kansas distinction is that Siberian and lacebark elms largely shrug it off.

Hits American Elm, Siberian Elm, Chinese Elm (Lacebark Elm), and others

Emerald ash borer

Agrilus planipennis

An invasive beetle that has killed essentially every untreated ash in the areas it has reached, and it is still moving across Kansas county by county. An ash you want to keep has to be on a treatment program before it looks sick — once a third of the canopy is gone, the window has closed.

Hits Green Ash, and others

Hypoxylon canker

Biscogniauxia atropunctata

A fungus that lives quietly inside healthy oaks and only turns destructive when the tree is severely stressed — most often by drought. Bark sloughs away in sheets to reveal a silver-grey crust, and by the time you can see it, that part of the tree is already dead.

Hits Bur Oak, Northern Red Oak, Pin Oak, and others

Oak wilt

Bretziella fagacearum

A fungal disease that plugs the water-conducting vessels of an oak from the inside. Red oaks can go from healthy to dead in a single season, and because it also travels underground through grafted roots, one infected tree threatens every oak near it.

Hits Northern Red Oak, Pin Oak, Bur Oak, and others

Pine wilt

Bursaphelenchus xylophilus

A microscopic nematode carried tree to tree by pine sawyer beetles, which multiplies inside a pine and shuts down its water supply. A mature Scots or Austrian pine can go from green to entirely brown in a matter of weeks, and there is no treatment once it is infected.

Hits Austrian Pine, and others

Borers

Beetle and moth larvae that tunnel through the living tissue just under the bark. With the sole exception of emerald ash borer, they are opportunists that attack trees already weakened by drought, heat, or damage — which makes an infestation a diagnosis of the tree's history, not just its pests.

Hits Bur Oak, Northern Red Oak, Pin Oak, Eastern Cottonwood, Silver Maple, Eastern Redbud, and others

Cankers

Localized dead patches in the bark and the living layer beneath it, caused by fungi that get in through wounds or take advantage of a stressed tree. Almost every canker fungus in Kansas is an opportunist, which means the canker is usually the second thing that went wrong.

Hits Eastern Cottonwood, Silver Maple, Honey Locust (thornless), Green Ash, Eastern Redbud, and others

Fire blight

Erwinia amylovora

A bacterial disease that runs down shoots from the blossoms in warm wet spring weather, leaving branches that look genuinely scorched. In Kansas it is above all a Callery and Bradford pear problem, on a tree that already has other reasons to come out.

Hits Bradford (Callery) Pear, and others

Root and butt rot

Fungi that decay roots and the base of the trunk, out of sight, for years before anything shows above ground. It is the leading cause of whole-tree failure in Kansas wind, and the most important thing about it is that a full green canopy is not evidence against it.

Hits Silver Maple, Pin Oak, Bradford (Callery) Pear, Eastern Cottonwood, Siberian Elm, and others

Bagworms

Thyridopteryx ephemeraeformis

Caterpillars that build a spindle-shaped bag out of the plant they are eating and drag it around as they feed. Entirely controllable — but only inside a narrow early-summer window, and on evergreens the cost of missing that window can be the whole tree.

Hits Eastern Red Cedar, Austrian Pine, Honey Locust (thornless), and others

Iron chlorosis

Yellowing caused not by a shortage of iron in Kansas soil but by soil too alkaline for the tree to take the iron up. It is the classic Kansas planting mistake made visible, and on the species that suffer it, the honest long-term answer is often a different tree.

Hits Pin Oak, Silver Maple, Eastern Redbud, American Sycamore, and others

Scale insects

Insects that spend most of their life immobile under a waxy shell fixed to bark or leaves, looking far more like a growth than an animal. Heavy infestations cause branch dieback, and there is exactly one short window each year when they can be reached.

Hits Silver Maple, Honey Locust (thornless), Eastern Redbud, White Mulberry, Pin Oak, and others

Spider mites

Not insects but relatives of spiders, small enough that most people diagnose them from the damage rather than the animal. Kansas summers — hot, dry, and dusty — are close to ideal for them, and the standard homeowner response of reaching for an insecticide reliably makes them worse.

Hits Austrian Pine, Eastern Red Cedar, Honey Locust (thornless), Boxelder, Silver Maple, and others

Anthracnose

A group of fungal leaf and shoot diseases that arrive in cool wet springs, disfigure the first flush of foliage, and are almost always over by midsummer. Alarming to look at on a sycamore, and very rarely a threat to an established tree.

Hits American Sycamore, Green Ash, Silver Maple, Bur Oak, White Mulberry, and others

Aphids

Soft-bodied insects that feed on sap and excrete the sticky residue that coats cars, patios, and anything else parked under an infested tree. Spectacularly annoying, essentially never fatal, and usually best handled by doing nothing at all.

Hits Silver Maple, Common Hackberry, Honey Locust (thornless), Boxelder, Eastern Redbud, and others

Cedar-apple rust

Gymnosporangium juniperi-virginianae

A fungus that needs two different hosts to complete its life cycle — a juniper or red cedar and an apple, crabapple, or hawthorn — and produces bright orange gelatinous horns on the cedar in spring rain. Startling to look at, and almost entirely harmless to the cedar.

Hits Eastern Red Cedar, and others