Upper Arlington, Ohio · Plant Health Care
I time tree care to the season's actual heat, not the calendar date. Here's where Upper Arlington sits today — which pests are working, on which trees, this week — and what's coming next. Live, from the same growing-degree-day model I run on client properties.
The calendar above shows where Upper Arlington sits today. This is the whole season — every pest and disease I track here, grouped by the tree it works on, with the window it runs in a normal year. Timings are growing-degree-day thresholds converted to calendar dates, so a warm spring moves them earlier and a cold one moves them later.
Opens early April, into mid May · peak around mid April
Inchworms dangling on silk threads from the canopy in May. Healthy trees refoliate; it is the third consecutive year of defoliation that does real harm.
UMD Extension Pest-Predictive Calendar
Opens mid April, into mid May · peak around late April
The clean round holes that appear in oak leaves every May and set off a round of panicked calls. The adult fly punctures the folded leaf before it expands, so one puncture opens into a neat symmetrical pattern of holes. Entirely cosmetic — no treatment, ever.
UMD Extension Pest-Predictive Calendar
Opens late April, into mid July · peak around early June
THE most important window on this calendar for oaks. These beetles feed on the fungal mats of oak-wilt-killed trees, then fly straight to any fresh oak wound and inoculate it. A single pruning cut in this window can kill a healthy red oak. Do not prune, wound, or climb-spur an oak from roughly April through mid-July — if a storm breaks a limb, seal the wound the same day.
OSU Buckeye Yard & Garden; USDA Forest Service oak wilt guidance
Opens early May, into late May · peak around mid May
Young caterpillars climbing to the canopy; oaks are hit first. Best window for Btk on small larvae.
UMD Extension Pest-Predictive Calendar; USA-NPN
Opens late May, into mid August · peak around early July
The oak equivalent of EAB, and the one that finishes off oaks already weakened by drought, construction damage, or defoliation. Dieback starts at the top of the crown and works down. There is no rescue treatment worth the money once the top third is gone — the intervention is water and root-zone care in the years BEFORE it shows up.
UMD Extension Pest-Predictive Calendar; USDA Forest Service
Opens early June, into mid June · peak around early June
Crawlers settling on twigs; honeydew and sooty mold on the leaves below.
UMD Extension Pest-Predictive Calendar
Opens late June, into late September · peak around early August
A red-group oak that browns from the top down and sheds half-green, bronze-tipped leaves in midsummer needs to be looked at THIS WEEK, not next season — a red oak can go from first symptom to dead in a matter of weeks, and the fungus then moves to neighbors through grafted roots. White-group oaks decline far more slowly. Confirming it means a lab sample, and the response is trenching to sever root grafts plus removal on a strict schedule.
Approximate window — mapped from calendar guidance, not a published degree-day threshold. Scout before you act.
OSU Buckeye Yard & Garden; USDA Forest Service oak wilt guidance (calendar timing mapped to GDD)
Opens late July, into early August · peak around late July
Crawlers on bark of pin/red/willow oaks; a stubborn armored scale — hit the crawler window.
UMD Extension Pest-Predictive Calendar
Opens late July, into mid September · peak around late August
Late-season oak defoliator; black caterpillars with orange stripes feeding in dense colonies, and a rain of frass on the patio below. Damage looks alarming but an established oak has already made its year of food by now.
Approximate window — mapped from calendar guidance, not a published degree-day threshold. Scout before you act.
UMD Extension Pest-Predictive Calendar; OSU Buckeye Yard & Garden (tail derived from calendar timing)
Opens early August, into early October · peak around late August
Overlapping generations build all season, so the damage peaks in August and September when everyone assumes the oak is dying. The leaf goes pale and stippled from above; underneath you will find the shiny black tar-spots of frass and the clear lace-patterned wings. White-oak group takes it worst. It is a stress additive, not a killer — water the root zone and let the predators catch up.
Approximate window — mapped from calendar guidance, not a published degree-day threshold. Scout before you act.
UMD Extension Pest-Predictive Calendar; OSU Buckeye Yard & Garden (late window derived from calendar timing)
Opens early August, through the season's end · peak around early September
The white felt on lilac leaves every August. Unlike most fungal problems it does not need leaf wetness — humid nights and crowded, shaded, still air are enough. Cosmetic on an established plant and it arrives too late in the season to cost the plant anything. Thin for airflow; do not spray.
Approximate window — mapped from calendar guidance, not a published degree-day threshold. Scout before you act.
OSU Buckeye Yard & Garden; Missouri Botanical Garden (calendar timing mapped to GDD)
Opens early August, into late September · peak around late August
Yellow-and-black striped colonies with a bright orange collar, defoliating one branch at a time on an otherwise untouched tree. Same unison head-and-tail rearing display as the walnut caterpillar. Late enough in the year to be a non-event for a healthy tree — prune out the one occupied limb.
Approximate window — mapped from calendar guidance, not a published degree-day threshold. Scout before you act.
OSU Buckeye Yard & Garden; UMD Extension (calendar timing mapped to GDD)
Opens mid August, through the season's end · peak around early September
Specific to bur oak and it builds year over year rather than blowing through once. Wedge-shaped dead areas spread along the leaf veins in late summer, worst in the lower and inner canopy, and the killed leaves hang on through winter instead of dropping. Those retained petioles carry the fungus into next spring — which is why it compounds. Distinguish it from ordinary anthracnose before recommending anything.
Approximate window — mapped from calendar guidance, not a published degree-day threshold. Scout before you act.
Iowa State University Plant & Insect Diagnostic Clinic; OSU Buckeye Yard & Garden (calendar timing mapped to GDD)
Opens late October, through the season's end · peak around early December
The last event of the tree year, and it is triggered by the first hard FROSTS rather than by accumulated heat — so treat this band as "after the leaves are down," not as a degree-day reading. Wingless females walk UP the trunk on mild November nights to lay the egg bands that hatch into next spring’s inchworms. Because she has to climb, a sticky band around the trunk now is one of the few genuinely effective mechanical controls left in the trade.
Approximate window — mapped from calendar guidance, not a published degree-day threshold. Scout before you act.
OSU Buckeye Yard & Garden; UMD Extension (calendar timing mapped to GDD)
Opens early April, into late May · peak around early May
A cool, wet spring drives it; a dry one makes it vanish. Blotchy dead areas following the leaf veins, and on sycamore whole shoots die back and refoliate. It looks alarming and is almost never a threat to an established tree — rake and remove the fallen leaves and let it go.
Approximate window — mapped from calendar guidance, not a published degree-day threshold. Scout before you act.
OSU Buckeye Yard & Garden; Purdue Plant & Pest Diagnostic Lab (calendar timing mapped to GDD)
Opens early April, into early May · peak around mid April
Toothpick-thin strands of frass pushed out of pinholes in the trunk — the unmistakable sign. They attack trees already stressed by flooding or transplant shock, so the fix is the stress, not the beetle.
UMD Extension Pest-Predictive Calendar; NC State Extension
Opens early May, into late May · peak around mid May
Green, undamaged sugar-maple leaves carpeting the lawn in late May, each one snapped off with a short clean stub of stem. That is this sawfly, not a disease and not drought. It takes a tiny fraction of the canopy — no treatment is warranted.
UMD Extension Pest-Predictive Calendar
Opens early June, into mid June · peak around early June
Crawlers on the move; heavy honeydew and sooty mold follow. Oil the crawler window.
UMD Extension Pest-Predictive Calendar
Opens early June, into late June · peak around mid June
White cottony egg masses on twigs are the biofix; crawlers hatch and move to leaves.
UMD Extension Pest-Predictive Calendar
Opens mid June, into late June · peak around mid June
Crawlers on the bark of (especially red) maples — the one window contact controls reach them.
UMD Extension Pest-Predictive Calendar
Opens mid June, into late September · peak around early August
A soil fungus that plugs the water-conducting tissue, so a single limb or one whole side of a maple wilts and browns while the rest looks fine. Peel the bark on a wilting branch and look for olive-green to black streaking in the sapwood — that streak is the diagnosis. There is no cure and no soil fumigation worth doing; water, mulch, and modest nitrogen buy years, sometimes many.
Approximate window — mapped from calendar guidance, not a published degree-day threshold. Scout before you act.
OSU Buckeye Yard & Garden; Purdue Plant & Pest Diagnostic Lab (calendar timing mapped to GDD)
Opens mid June, into early August · peak around early July
Adults skeletonizing leaves; lindens and crabapples are magnets. Damage is cosmetic on established trees.
UMD Extension Pest-Predictive Calendar; Iowa State
Opens early July, into early October · peak around mid August
A federally regulated pest under active eradication in Ohio (Clermont County). Maple is the preferred host. The signs are unmistakable and unlike anything native: perfectly round exit holes about the diameter of a pencil, oval egg-laying pits chewed into the bark, and coarse sawdust at branch unions. If you think you see it, do not treat and do not move the wood — photograph it and report to the Ohio Dept. of Agriculture.
Approximate window — mapped from calendar guidance, not a published degree-day threshold. Scout before you act.
USDA APHIS ALB program; Ohio Dept. of Agriculture (adult window derived from calendar timing)
Opens early August, through the season's end · peak around early September
Rarely a threat to the tree — but the honeydew is why people call. A sticky film on the car, the patio furniture and the sidewalk under a linden or maple, then black sooty mold growing on the film, then wasps working the drip. Ladybird and lacewing larvae usually crash the colony within a couple of weeks if a broad-spectrum spray has not wiped them out first. A hard hose-down and patience is genuinely the right answer most of the time.
Approximate window — mapped from calendar guidance, not a published degree-day threshold. Scout before you act.
OSU Buckeye Yard & Garden; UMD Extension (flush-driven; calendar timing mapped to GDD)
Opens mid August, into late September · peak around early September
An armored scale that is genuinely hard to see — the covers look like small white-gray flecks of bark, and infestations are usually well advanced before anyone notices thinning and dieback. Long, staggered crawler emergence means one oil application will not clear it.
Approximate window — mapped from calendar guidance, not a published degree-day threshold. Scout before you act.
UMD Extension Pest-Predictive Calendar; Rutgers Nursery IPM (2nd-gen window derived from calendar timing)
Opens late August, through the season's end · peak around late September
Ohio’s newest quarantine pest and it is moving west. Black-and-white spotted nymphs early, then the red-winged adult. Heavy honeydew and black sooty mold under the tree is often the first thing people notice. Scrape the gray putty-like egg masses off trunks and stone through the winter, and report a find to ODA.
Approximate window — mapped from calendar guidance, not a published degree-day threshold. Scout before you act.
Penn State Extension SLF phenology; Ohio Dept. of Agriculture (egg-laying window derived from calendar timing)
Opens early May, into early June · peak around mid May
Clearwing-moth flight; stressed or wounded stems are the egg-laying targets.
UMD Extension Pest-Predictive Calendar
Opens early May, into late May · peak around mid May
Armored scales shaped exactly like tiny oyster shells, packed so tight on the bark they read as bark texture. Scrape a patch with a thumbnail — if it flakes off in shells, that is the infestation. Crawlers are the only exposed stage.
UMD Extension Pest-Predictive Calendar
Opens early May, into early August · peak around mid June
Adults flying and laying eggs through summer. Untreated ash is at risk; systemic trunk injections are placed pre-emergence, so this is the marker to be on a program by.
UMD Extension Pest-Predictive Calendar; USA-NPN
Opens late March, into early May · peak around mid April
Silk tents forming in branch crotches; small caterpillars are easiest to knock out now.
UMD Extension Pest-Predictive Calendar
Opens early April, into late May · peak around early May
Infection happens NOW, in spring rain, but you will not see it until the crabapple drops half its leaves in July and everyone assumes it is dying of something else. Olive-brown velvety leaf spots are the tell. The durable fix is a scab-resistant cultivar, not an annual spray.
Approximate window — mapped from calendar guidance, not a published degree-day threshold. Scout before you act.
OSU Buckeye Yard & Garden; Michigan State Extension (calendar timing mapped to GDD)
Opens late April, into late May · peak around early May
Slimy, olive-green slug-like larvae that skeletonize the upper leaf surface, leaving a windowpane of veins. A hard jet of water knocks them off and they cannot climb back.
UMD Extension Pest-Predictive Calendar
Opens early May, into late August · peak around early June
A very long flight — the moths are laying eggs from May into September, and they target bark that is already wounded. Mower and string-trimmer scars at the base of a landscape dogwood are the classic entry point. Mulch the base properly and the borer never gets a door.
UMD Extension Pest-Predictive Calendar
Opens late July, into early October · peak around mid August
Crawlers emerge late summer — the one window horticultural oil / contact control works before they armor up.
Approximate window — mapped from calendar guidance, not a published degree-day threshold. Scout before you act.
OSU / Rutgers Nursery IPM; The Morton Arboretum (tail derived from calendar timing)
Opens late July, into late September · peak around late August
Silk nests enveloping branch TIPS — that is what separates it from eastern tent caterpillar, which builds in the crotches in spring. The second generation is the conspicuous one, draping whole limb ends in late summer. Damage this late in the season costs the tree essentially nothing; pull the nests down with a pole if they bother you.
Approximate window — mapped from calendar guidance, not a published degree-day threshold. Scout before you act.
UMD Extension Pest-Predictive Calendar; OSU Buckeye Yard & Garden (2nd-gen tail derived from calendar timing)
Opens mid August, into early October · peak around late August
One of the largest soft scales in the region — hemispherical, pink-orange mottled bumps crowded along the twigs. The honeydew is torrential: cars, decks and understory plants under an infested tuliptree go black with sooty mold, and that is usually the complaint that brings me out. Late-summer crawler emergence is the only exposed window.
Approximate window — mapped from calendar guidance, not a published degree-day threshold. Scout before you act.
OSU Buckeye Yard & Garden; Rutgers Nursery IPM (calendar timing mapped to GDD)
Opens early May, into late June · peak around late May
Adult flight; drought-stressed and white-barked birches are most at risk. Keep birches watered.
MSU Enviroweather (GDD of Landscape Insects)
Opens early May, into early June · peak around mid May
Larvae skeletonize the underside and the canopy turns lace-brown from the inside out. The second generation is the one that does visible damage, and the adults are also the beetle that turns up indoors overwintering.
UMD Extension Pest-Predictive Calendar
Opens early May, into late June · peak around early June
Attacks newly planted and sun-scalded trees — the southwest side of a thin-barked young trunk sitting in open lawn is the target. Flattened, discolored, slightly sunken bark is the sign. Shade the trunk and keep the root ball watered through establishment.
UMD Extension Pest-Predictive Calendar
Opens early May, into late May · peak around mid May
Nymphs feeding on emerging leaflets; distorted, stunted new growth is the tell.
UMD Extension Pest-Predictive Calendar
Opens early June, into late August · peak around mid July
Honeylocust that goes bronze and drops its leaflets early in a hot dry August is usually this, not disease. Hot weather accelerates it, and a broad-spectrum insecticide makes it worse by killing the predatory mites.
UMD Extension Pest-Predictive Calendar
Opens late July, into early October · peak around late August
Whole hillsides of black locust turn scorched red-brown in August and read as fire damage or drought kill from a distance. The larvae mine between the leaf surfaces. Black locust has coped with this every year for a very long time — it refoliates and it is fine.
Approximate window — mapped from calendar guidance, not a published degree-day threshold. Scout before you act.
OSU Buckeye Yard & Garden; USDA Forest Service (calendar timing mapped to GDD)
Opens late July, into late September · peak around late August
Generations stack all summer until the whole canopy goes chlorotic and gray-stippled by August. Turn a leaf over: the lace-winged adults and the varnish-like black specks of frass are unmistakable. On a mature sycamore this is cosmetic and self-correcting.
Approximate window — mapped from calendar guidance, not a published degree-day threshold. Scout before you act.
UMD Extension Pest-Predictive Calendar; OSU Buckeye Yard & Garden (late window derived from calendar timing)
Opens early August, into late September · peak around late August
Dense colonies that strip one limb at a time, and when disturbed the whole mass rears up head-and-tail in unison. They gather on the trunk in a writhing mat to molt — which is the moment to scrape them off into soapy water and be done with it.
Approximate window — mapped from calendar guidance, not a published degree-day threshold. Scout before you act.
OSU Buckeye Yard & Garden; Purdue Extension (calendar timing mapped to GDD)
Opens mid August, into mid September · peak around late August
Webbing and browning at branch tips on honeylocust; worst on "Sunburst"/"Skyline".
UMD Extension Pest-Predictive Calendar
Opens early September, through the season's end · peak around early October
Fall is when this one finally shows itself: clusters of honey-colored mushrooms at the base of the trunk or over the root plate after cool autumn rain. Peel the bark at the collar and you find flat white fans of mycelium and the black bootlace rhizomorphs. It is a decay organism on a compromised root system, so a mushroom cluster on a tree with a thinning crown is a structural question, not a spray question — get it assessed for target risk.
Approximate window — mapped from calendar guidance, not a published degree-day threshold. Scout before you act.
OSU Buckeye Yard & Garden; USDA Forest Service (fruiting window derived from calendar timing)
Runs as the season opens into mid April · peak around mid March
Adults walk up to the previous year’s terminal leader on the first warm days and feed at the tip. You will not see the damage until the leader wilts into a shepherd’s crook in June — this is the window to act, not that one.
UMD Extension Pest-Predictive Calendar
Runs as the season opens into early April · peak around mid March
Popcorn-like pitch masses at branch whorls; larvae tunnel where limb meets trunk and whole branches flag. Two narrow windows a year reach them — spring green-up and mid-August.
UMD Extension Pest-Predictive Calendar; MSU Enviroweather
Opens late March, into mid April · peak around early April
Colonies of gray-green larvae rear up together when disturbed. They eat only last year’s needles, so the tree survives — but a mugo can be stripped bare in a week. Knock them off by hand while the colony is still one clump.
UMD Extension Pest-Predictive Calendar
Opens early April, into mid May · peak around early May
Bright orange gelatinous horns swell out of brown galls on juniper during warm spring rain, and the spores blow to crabapple and hawthorn. It needs BOTH hosts to complete the cycle — the orange leaf spots you see on the crabapple in June were set in motion here.
Approximate window — mapped from calendar guidance, not a published degree-day threshold. Scout before you act.
OSU Buckeye Yard & Garden; Missouri Botanical Garden (calendar timing mapped to GDD)
Opens mid April, into mid May · peak around late April
Crawlers settling at needle bases; scout for white "wool." Main control is dormant-oil in fall/early spring.
UMD Extension Pest-Predictive Calendar; USA-NPN
Opens mid April, into early June · peak around mid May
Austrian pine is the classic host in central Ohio. New candles are infected during spring rain and die back stunted with the needles still half-length, resin running. It works from the bottom of the tree upward over years. Do not prune or shear pines while they are wet.
Approximate window — mapped from calendar guidance, not a published degree-day threshold. Scout before you act.
OSU Buckeye Yard & Garden; Purdue Plant & Pest Diagnostic Lab (calendar timing mapped to GDD)
Opens late April, into mid May · peak around early May
Nymphs under a waxy white fluff cup the new leaves into a little cabbage at the shoot tip. Cosmetic on an established hedge; shearing in spring takes most of it out with the tips.
UMD Extension Pest-Predictive Calendar
Opens late April, into mid May · peak around early May
Reddish crawlers under the white "flecks" on needles; oil the crawler window.
UMD Extension Pest-Predictive Calendar; USA-NPN
Opens early May, into late May · peak around mid May
Tiny orange gnats swarming the boxwood for a few days — that brief flight is the treatable window. The blistered, blotchy leaves you already see were made by last year’s generation.
UMD Extension Pest-Predictive Calendar
Opens early May, into late June · peak around early June
The reason so many Colorado blue spruce in this town are bare from the bottom up. New needles are infected NOW in wet spring weather, but they do not brown and drop until a year later — which is why treating the symptom always feels like it failed. Look for rows of tiny black dots in the needle stomata under a hand lens.
Approximate window — mapped from calendar guidance, not a published degree-day threshold. Scout before you act.
OSU Buckeye Yard & Garden; Michigan State Extension (calendar timing mapped to GDD)
Opens late May, into early June · peak around early June
Larvae hatching and building small bags; treat while bags are little — big bags shrug off sprays.
UMD Extension Pest-Predictive Calendar; USA-NPN
Opens mid June, into early August · peak around early July
Unlike the European pine sawfly, this one eats BOTH old and new needles — so it can actually kill a young pine. Colonies of red-headed, yellow, black-spotted larvae feeding shoulder to shoulder.
UMD Extension Pest-Predictive Calendar
Opens late June, into early October · peak around mid August
The HOT-season mite — the mirror image of spruce spider mite. It explodes in exactly the dusty, drought-stressed, reflected-heat spots: a burning bush against a south wall, an arborvitae hedge along a driveway. Fine stippling, then bronzing, then webbing. Hosing the foliage down repeatedly does most of the work.
Approximate window — mapped from calendar guidance, not a published degree-day threshold. Scout before you act.
UMD Extension Pest-Predictive Calendar; OSU Buckeye Yard & Garden (window derived from calendar timing)
Opens early September, through the season's end · peak around early October
A COOL-season mite — it peaks in spring and again in fall and goes quiet in midsummer heat, which is exactly backwards from what most people expect. Tap a branch over white paper: moving specks confirm it. Stippled, bronzed inner needles are the damage.
Approximate window — mapped from calendar guidance, not a published degree-day threshold. Scout before you act.
UMD Extension Pest-Predictive Calendar; OSU Buckeye Yard & Garden (fall window derived from calendar timing)
Opens early April, into mid May · peak around late April
Larvae and then adults skeletonize the same shrub twice in one season, and three consecutive years of it kills the plant. Arrowwood viburnum is the favorite. The overwintering egg sites are visible as rows of raised bumps on last year’s twigs — prune those out in winter and you break the cycle without spraying anything.
UMD Extension Pest-Predictive Calendar; Cornell Viburnum Leaf Beetle Citizen Science
Opens mid May, into early June · peak around late May
Crawlers exposed and vulnerable to horticultural oil; heavy infestations kill euonymus.
UMD Extension Pest-Predictive Calendar
Advisory, not a spray date. Degree-day windows tell you when to look, not when to treat. What a tree actually needs depends on what is on it, how much, and whether it matters — which is a thing to look at, not to guess at. Text me and I will tell you straight.
A calendar tells you what is possible in Upper Arlington this week. It cannot tell you what is on the maple by your driveway — and the difference between a cosmetic leaf spot and the borer that ends the tree is not something to guess at from a list. CanopyKeep is the free tree-intelligence tool we built: three photos of the tree, or of the leaf, hole, or insect that worries you, and it comes back with the species, what is wrong, and what to do about it this week.
Open CanopyKeep — Free →No account needed. Works on any phone.