National Snapshot

Disease takes the headline this week

A busy week on the tree-disease front. Laurel wilt has jumped north to Long Island, where New York just quarantined five Suffolk County towns; elm zigzag sawfly keeps expanding across the Mid-Atlantic; and oak wilt and box tree moth quarantines remain in force. On the insect side, magnolia and soft scales are dripping honeydew with crawlers due any day, late-summer caterpillars are defoliating oaks and maples, spotted lanternfly adults are everywhere, and spider mites hold in the heat.

Disease

New disease moves: laurel wilt is now quarantined on Long Island (see the featured pest); elm zigzag sawfly is spreading; oak wilt and box tree moth quarantines stay active. Details in the Disease Watch below.

Sap feeder

Magnolia & soft scales are peaking for honeydew and sooty mold — crawlers emerge any day into late August, the one window when oil and IGRs land. Monitor twigs with tape now.

Caterpillar

Late-summer defoliators — orangestriped oakworm and greenstriped mapleworm on oaks and maples, plus yellownecked and walnut caterpillars — are active as fall webworm nests grow large.

Invasive

Spotted lanternfly adults are widespread on woody trees; honeydew, sooty mold, and yellowjackets follow. Egg-laying begins in late September — scout and report.

Mite

Spider mites hold near their peak in the heat and drought — two-spotted, oak, and spruce mites bronze foliage on dusty, water-stressed canopies.

Borer

Ambrosia & wood borers — the redbay ambrosia beetle that vectors laurel wilt, plus EAB (flight winding down) and clearwing borers. The rule for all of them: don't move wood.

Methodology Note

How we report growing degree days

Growing degree days accumulate from January 1 and only climb through the season. Each region's reading is anchored to the latest measured cooperative-extension station data (base 50°F), so figures track real, on-the-ground heat rather than the calendar. Because published station data can lag by a week or two, always confirm against your nearest local station (NEWA, Enviroweather, or your state tool) before timing an application.

Pest on the Chart · This Week

Laurel Wilt

Harringtonia lauricola

This week's pest on the chart is a disease making news close to home. Laurel wilt — a lethal vascular wilt vectored by the invasive redbay ambrosia beetle — has killed redbay, sassafras, and avocado across the Southeast for two decades. This week it took a major step north: New York established a quarantine across five Suffolk County towns (Huntington, Babylon, Smithtown, Islip, and Brookhaven) after the first New York detection last year — the northernmost occurrence in the U.S. Native sassafras and spicebush are the hosts at risk in the Northeast, and infected trees die fast. In the Southeast the front keeps advancing, with North Carolina now at 21 positive counties.

Vector

Ambrosia beetle

At-Risk Hosts

Sassafras

Rx Note

Don't move wood

℞ — There is no cure, so containment is everything. Don't move sassafras or spicebush wood — or untreated firewood of any species — out of a known area; chip dead material to under an inch and mulch it on-site. Scout hosts for sudden wilt, dark sapwood streaking, and toothpick-like frass tubes, and report suspect trees to your state program. For high-value specimens near an active front, preventive propiconazole injection and vector management offer limited, temporary protection only.

Regional Disease Watch

Beyond laurel wilt (this week's featured pest), three more quarantine-driven threats are on the move. The common thread: scout the host, report new finds, and don't move wood.

Mid-Atl / NE / SE

Elm zigzag sawfly (Aproceros leucopoda) — an emerging elm defoliator that leaves a distinctive zigzag mining trail before eating whole leaves. Now confirmed across VA, MD, PA, NY, VT, NC, and TN, and recently found on Japanese zelkova. Scout elms; healthy trees usually tolerate it — monitor and report new areas.

New York

Oak wilt (Bretziella fagacearum) — the Finger Lakes quarantine (Middlesex, Italy, South Bristol, and parts of Bristol & Naples) stays in force, and Monroe County's Town of Greece detection stands from July with no new counties this week. Keep oaks unpruned into September and don't move oak wood.

Maryland

Box tree moth (Cydalima perspectalis) — MDA's quarantine covers Washington, Frederick, Garrett, and Allegany counties. Monitor boxwood April–October for chewing damage and webbing, report finds, and skip preventive blanket sprays.

℞ Early detection is the only cheap tool left. Know each host, scout it deliberately, report new municipalities to your state program, and keep host wood and firewood local — movement of wood is how nearly all of these jump to new regions.

Regional Rx · 5 Zones

Read your zone like a chart

Each card reports the region's growing-degree-day reading (the vital sign that drives every timing call), what's active now (Diagnose), and how to time treatment (℞). GDD ranges are typical for the week, base 50°F from Jan 1 — always confirm against your nearest station.

NE

Northeast & New England

                                                                ME · NH · VT · MA · RI · CT · NY
                                                              

GDD · Accumulated

~1,600–2,000

0

1,500

3,000+

Conditions: Accumulation advancing from a July 8 UMass base of ~1,094 (base 50°F). Drought remains severe on the Cape with widespread scorch and premature leaf drop. New this week: a laurel wilt quarantine on Long Island (Suffolk Co.).

Dx

Diagnose · Active Now

•

Laurel wilt quarantine on Long Island — scout sassafras and spicebush; oak wilt stands in the Finger Lakes and Monroe Co.

•

Magnolia scale females conspicuous with heavy honeydew; cottony camellia & lecanium scale active.

•

Spotted lanternfly adults on tree-of-heaven and grape; fall webworm nests enlarging.

•

Two-spotted & oak spider mites at peak; late-summer caterpillars building.

•

Drought scorch and bacterial leaf scorch both browning canopies — confirm before treating.

℞

Prescribe · Timing & Materials

•

Laurel wilt / oak wilt: don't move host wood or firewood; report suspect sassafras, spicebush, and oaks; hold oak pruning into September.

•

Magnolia / soft scale: tape-monitor twigs and time horticultural oil + IGR to the imminent crawlers.

•

Fall webworm & caterpillars: prune small nests; Btk / spinosad on young larvae; tolerate on large, healthy trees.

•

Drought: deep-water high-value trees; confirm scorch by lab before committing to a plan.

MA

Mid-Atlantic & DMV

                                                                NY · NJ · PA · MD · DE · DC · VA · WV
                                                              

GDD · Accumulated

~2,250–2,800

0

1,500

3,000+

Conditions: Warm and humid with high foliar-disease pressure. SLF adults are heavy in central Maryland and visiting trap trees. Watch two spreading pests: elm zigzag sawfly and box tree moth (MDA quarantine in four western counties).

Dx

Diagnose · Active Now

•

Elm zigzag sawfly spreading on elms (telltale zigzag mining); box tree moth quarantine active on boxwood.

•

Bacterial leaf scorch symptoms strong on oaks, elms, and sycamore.

•

Spotted lanternfly adults heavy on woody trees; magnolia scale honeydew.

•

Orangestriped oakworm & yellownecked caterpillars; fall webworm nests enlarging.

•

Sycamore & oak lace bugs stippling; crapemyrtle bark scale + aphid sooty mold.

℞

Prescribe · Timing & Materials

•

Elm zigzag sawfly: scout elms and report new areas; healthy elms usually tolerate defoliation — treat only high-value or repeatedly defoliated trees.

•

Box tree moth: monitor boxwood Apr–Oct; Btk / spinosad / chlorantraniliprole on active larvae; skip preventive blanket sprays; report.

•

Bacterial leaf scorch: confirm by lab; no cure — support vigor, and consider oxytetracycline injection for high-value trees.

•

Magnolia scale: time horticultural oil + IGR to late-August crawlers.

•

Spotted lanternfly: treat tree-of-heaven trap trees so visiting adults are killed; scout and report.

SE

Southeast

                                                                NC · SC · GA · TN · AL · MS · FL · VA
                                                              

GDD · Accumulated

~2,950–3,950

0

1,500

3,000+

Conditions: Hot and humid; the season's furthest along. Laurel wilt keeps advancing (North Carolina now at 21 positive counties), and southern pine beetle pressure runs high on stressed pines.

Dx

Diagnose · Active Now

•

Laurel wilt expanding — NC adds Beaufort and Greene counties (21 total); scout redbay, sassafras, and bay.

•

Southern pine beetle active on stressed pines; ambrosia beetles on hardwoods.

•

Crapemyrtle bark scale + crape myrtle aphid driving heavy sooty mold.

•

Orangestriped oakworm defoliating pin and willow oaks; fall webworm large nests.

•

Oak & azalea lace bugs; southern red spider mite; Cercospora & powdery mildew on crape myrtle.

℞

Prescribe · Timing & Materials

•

Laurel wilt / pine & ambrosia borers: don't move host wood or firewood; reduce stress; report suspect laurel-family trees.

•

Crapemyrtle bark scale: systemic imidacloprid / dinotefuran drench timed to avoid bloom, IGR at crawlers, dormant hort oil; wash sooty mold.

•

Caterpillars: tolerate on large trees; handpick oakworm clusters; prune webworm nests or Btk on young larvae.

•

Lace bugs: hort oil / insecticidal soap on nymph undersides.

•

Crape myrtle disease: resistant cultivars, airflow, labeled myclobutanil / propiconazole.

MW

Midwest & Great Lakes

                                                                OH · MI · IN · IL · WI · MN · IA · MO
                                                              

GDD · Accumulated

~2,050–2,650

0

1,500

3,000+

Conditions: Running ~2 weeks ahead. Japanese beetle is tapering; dry pockets keep spider mites active. Watch oak wilt (widespread in Minnesota and the Great Lakes) and the still-spreading elm zigzag sawfly.

Dx

Diagnose · Active Now

•

Oak wilt risk high — warm-season oak wounds invite sap-beetle vectoring; elm zigzag sawfly spreading on elms.

•

Magnolia scale females conspicuous — crawlers expected late August.

•

Emerald ash borer flight winding down as larvae tunnel; Japanese beetle tapering.

•

Fall webworm nests enlarging; bagworm larvae now large in the southern Midwest.

•

Walnut & yellownecked caterpillars; spider mites in dry pockets.

℞

Prescribe · Timing & Materials

•

Oak wilt: do not prune oaks now; paint any unavoidable wounds immediately; don't move oak wood.

•

Magnolia scale: plan late-August crawler-timed horticultural oil + IGR; hose honeydew.

•

EAB: systemic trunk injection (emamectin benzoate) for high-value ash on cycle.

•

Webworm / bagworm: prune webworm nests; use chlorantraniliprole for large bagworm.

•

Elm zigzag sawfly: scout and report; treat only high-value, repeatedly defoliated elms.

W

West & Pacific

                                                                CA · OR · WA · NV · AZ · CO · UT · ID · MT
                                                              

GDD · Accumulated

Highly variable

Coast / high elev.

—

Inland / low desert

Conditions: Wide range by elevation and coast vs. inland; irrigation-driven stress is the key variable and fire season is in full swing across the interior West.

Dx

Diagnose · Active Now

•

Wood-boring beetles on stressed trees — invasive shothole borers in SoCal, goldspotted oak borer on oaks, Mediterranean oak borer.

•

Emerald ash borer in Oregon — five Willamette Valley counties remain under quarantine (Washington, Yamhill, Marion, Clackamas, Multnomah).

•

Spider mites at peak in heat and road dust; aphids with honeydew and sooty mold.

•

Bacterial blast / canker on stone fruit and citrus; yellowjackets building.

℞

Prescribe · Timing & Materials

•

Borers: deep-water summer-rainfall-adapted trees, avoid fresh wounds, and do not move ash material or firewood; in EAB zones, inventory ash and consider systemic protection, then report.

•

Spider mites: rinse dust, use hort oil or a selective miticide only if damaging; protect predators.

•

Aphids: strong water spray, conserve natural enemies, tolerate on established plants.

•

Stone-fruit canker/blight: prune out in dry weather, cutting several inches into healthy wood.

•

Fire: maintain defensible space and thin fuel ladders around trees and structures.

Field notes — read before you spray

Don't move wood. Laurel wilt, oak wilt, and box tree moth all hitchhike on firewood and host wood. Keep sassafras, spicebush, oak, and boxwood material local, and report new municipalities to your state program.

Catch scale at the crawler. Magnolia and soft-scale females are obvious now, but oil and IGRs only work on the crawlers due any day — tape-monitor twigs and mark the calendar.

Sample before you treat the scorch. Bacterial leaf scorch and drought both brown late-summer canopies with opposite fixes — confirm by lab when the pattern is unclear.

Sources · Cooperative Extension & USDA

Compiled from public reporting by cooperative extension and state/federal partners, including NY DEC & Ag and Markets (laurel wilt and oak wilt quarantines); Cornell Branching Out; UMass Extension; University of Maryland Extension & MDA (box tree moth); Rutgers; NC State, NC Forest Service & Clemson; Michigan State, Iowa State & UMN; UC Statewide IPM Program; Oregon Dept. of Agriculture / ODF; and USDA NIFA / Forest Service / APHIS. Regional summaries are paraphrased; consult the original bulletins and your local extension office for specifics.

Laurel wilt reaches Long Island, elm zigzag sawfly spreads, and magnolia scale crawlers are due — your region-by-region windows for Aug 3–10.

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