National field report October 16, 2026

The largest current group is closing: 97% of covered ZCTAs in GDD-tracked states.

The latest verified release places 22,119 of 22,798 covered ZCTAs in GDD-tracked states in the modeled preventive window closing band. The report rebuilds daily from the same citable GDD release used by the public data product. Alabama, Arizona, Arkansas, California, Florida, Georgia, Louisiana, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, and Texas follow published Extension months instead and are listed separately.

Check your ZIP's live status See all 50 states

The national pulse

The current distribution across four modeled timing bands

Below 800 GDD50

1.5%

Too early

351 ZCTAs

800–1,000 GDD50

0.6%

Approaching

134 ZCTAs

>1,000–1,300 GDD50

0.9%

Open

194 ZCTAs

Above 1,300 GDD50

97%

Closing

22,119 ZCTAs

GDD-tracked median 3,255.3 GDD50

The midpoint covered ZCTA is preventive window closing.

Geographic spread 2,057–4,597.3

The 10th–90th percentile range shows the current national geographic spread.

Station fallback 7,675 ZCTAs

Used a fresher alternate station in public release 2026-10-16.

Reusable national image

State medians show how the window differs across the country

State color is based on the median GDD50 among covered ZCTAs, while the all-state table preserves each state's full distribution. States that follow Extension months have their own color. State medians can hide local elevation, coastal, lake, urban, and station-to-station variation.

PNG 1200 × 630 share image SVG scalable publisher graphic CSV accessible 50-state dataset

Twelve states to watch

A closer look at twelve geographically varied states

Closing

Michigan

Median 2,765.9 GDD50; 0% open, 0% approaching, and 100% closing across 992 covered ZCTAs.

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Closing

Ohio

Median 3,384.2 GDD50; 0% open, 0% approaching, and 100% closing across 1,233 covered ZCTAs.

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Closing

Wisconsin

Median 2,738.3 GDD50; 0% open, 0% approaching, and 100% closing across 783 covered ZCTAs.

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Closing

Minnesota

Median 2,809.1 GDD50; 0% open, 0.5% approaching, and 99.5% closing across 880 covered ZCTAs.

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Closing

New York

Median 2,679.8 GDD50; 0% open, 0% approaching, and 100% closing across 1,826 covered ZCTAs.

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Closing

Massachusetts

Median 2,687.6 GDD50; 0% open, 0% approaching, and 100% closing across 539 covered ZCTAs.

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Closing

Connecticut

Median 2,961.9 GDD50; 0% open, 0% approaching, and 100% closing across 288 covered ZCTAs.

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Closing

Maine

Median 2,163.4 GDD50; 0% open, 0% approaching, and 100% closing across 427 covered ZCTAs.

Open Maine's ZIP tool

Closing

North Dakota

Median 2,488.8 GDD50; 0% open, 0% approaching, and 99% closing across 389 covered ZCTAs.

Open North Dakota's ZIP tool

Closing

Oregon

Median 2,313.8 GDD50; 5.1% open, 2.1% approaching, and 92.1% closing across 428 covered ZCTAs.

Open Oregon's ZIP tool

Closing

Washington

Median 2,091.1 GDD50; 6.8% open, 1.8% approaching, and 88.8% closing across 605 covered ZCTAs.

Open Washington's ZIP tool

Closing

Colorado

Median 3,350 GDD50; 2.3% open, 5.9% approaching, and 83.7% closing across 528 covered ZCTAs.

Open Colorado's ZIP tool

Read this before treating

A phenology signal is not a pesticide prescription

This report maps this site's operational 800–1,300 GDD50 bands. Those cut points are a broad planning cue tied most directly to Japanese beetle seasonal development—not a universal, research-validated application threshold for every grub species, active ingredient, lawn, or state.

Before using any pesticide, read and follow the current label on your container. It controls the allowed site, target pest, timing, rate, watering, application frequency, setbacks, and safety precautions. Product registrations and state restrictions can change. Confirm active grubs and consult local Extension guidance when species or timing is uncertain.

EPA: how to read legally enforceable pesticide labels

All-state summary

Every state, the same verified public release

Status is assigned from each state's median ZCTA GDD50. The four count columns show the underlying within-state distribution so a median does not masquerade as a uniform state.

Modeled preventive grub-control timing by state, generated October 16, 2026
State	Median GDD50	10th–90th pct.	Modeled status	Too early	Approaching	Open	Closing	Available ZCTAs
Alabama AL	5,902.6	5,153.4–6,460.9	Extension months	—	—	—	—	656
Alaska AK	450.3	89.5–820.5	Too early	217	26	2	0	245
Arizona AZ	7,633.3	3,032.7–9,239.4	Extension months	—	—	—	—	416
Arkansas AR	5,811.4	5,250.6–6,260	Extension months	—	—	—	—	614
California CA	4,907.2	2,924.7–5,932.8	Extension months	—	—	—	—	1,803
Colorado CO	3,350	882.7–4,164.8	Closing	43	31	12	442	528
Connecticut CT	2,961.9	2,468–3,188.7	Closing	0	0	0	288	288
Delaware DE	4,163	4,027.5–4,288	Closing	0	0	0	68	68
Florida FL	7,454	6,538.6–8,169.8	Extension months	—	—	—	—	1,013
Georgia GA	5,747.3	5,178.9–6,359	Extension months	—	—	—	—	751
Hawaii HI	7,331.1	2,369.6–7,927.4	Closing	2	0	0	95	97
Idaho ID	2,369.2	1,240.9–3,341.3	Closing	2	12	22	244	280
Illinois IL	3,817.5	3,266.7–4,773.5	Closing	0	0	0	1,396	1,396
Indiana IN	3,732.5	3,223.3–4,594.9	Closing	0	0	0	807	807
Iowa IA	3,459.1	3,041.5–3,926.4	Closing	0	0	0	970	970
Kansas KS	4,731.3	4,200.3–5,407.9	Closing	0	0	0	704	704
Kentucky KY	4,337.9	4,032.6–5,002.9	Closing	0	0	0	779	779
Louisiana LA	6,743.5	6,348.2–7,039.7	Extension months	—	—	—	—	539
Maine ME	2,163.4	1,656.4–2,524.7	Closing	0	0	0	427	427
Maryland MD	4,135.4	3,718.6–4,619.6	Closing	0	0	0	477	477
Massachusetts MA	2,687.6	2,321.2–3,187.3	Closing	0	0	0	539	539
Michigan MI	2,765.9	1,957.8–3,197.8	Closing	0	0	0	992	992
Minnesota MN	2,809.1	2,053.6–3,161.9	Closing	0	4	0	876	880
Mississippi MS	6,254.4	5,759.6–6,649.6	Extension months	—	—	—	—	427
Missouri MO	4,682.9	4,138.5–5,183.8	Closing	0	0	0	1,035	1,035
Montana MT	2,081.7	922.6–2,863.9	Closing	26	18	32	293	369
Nebraska NE	3,783.3	3,320.8–4,169	Closing	0	0	0	586	586
Nevada NV	3,855.1	1,435–8,073.8	Closing	3	0	9	168	180
New Hampshire NH	2,397.6	1,829–2,658.4	Closing	2	0	0	244	246
New Jersey NJ	3,748.2	3,200.4–4,003.1	Closing	0	0	0	598	598
New Mexico NM	3,475.2	1,448.2–5,780.1	Closing	14	2	16	341	373
New York NY	2,679.8	2,091.9–3,731.3	Closing	0	0	0	1,826	1,826
North Carolina NC	4,955.8	3,807.5–5,462.2	Extension months	—	—	—	—	853
North Dakota ND	2,488.8	2,139.5–2,855.3	Closing	4	0	0	385	389
Ohio OH	3,384.2	3,051.4–3,944.5	Closing	0	0	0	1,233	1,233
Oklahoma OK	6,051.7	5,370.7–6,369.5	Extension months	—	—	—	—	644
Oregon OR	2,313.8	1,399.9–3,035.8	Closing	3	9	22	394	428
Pennsylvania PA	3,160.2	2,467.2–3,828	Closing	0	0	0	1,833	1,833
Rhode Island RI	3,150.4	2,476.7–3,150.4	Closing	0	0	0	81	81
South Carolina SC	5,439.6	4,871–6,153.3	Extension months	—	—	—	—	424
South Dakota SD	3,113.3	2,607.6–3,490.7	Closing	0	0	1	374	375
Tennessee TN	5,076	4,265.7–5,769.3	Extension months	—	—	—	—	638
Texas TX	7,010.2	6,144.2–7,656.1	Extension months	—	—	—	—	1,989
Utah UT	2,828.9	1,271.7–4,393.2	Closing	7	8	17	267	299
Vermont VT	2,039	1,616.7–2,520.2	Closing	0	3	0	262	265
Virginia VA	4,301.8	3,479.5–4,894.2	Closing	0	0	0	903	903
Washington WA	2,091.1	1,287.2–2,910.8	Closing	16	11	41	537	605
West Virginia WV	3,658.2	2,723.1–4,194.7	Closing	0	0	0	738	738
Wisconsin WI	2,738.3	2,209.5–3,090.3	Closing	0	0	0	783	783
Wyoming WY	2,459.1	950.3–3,119.9	Closing	12	10	20	134	176

Need the values in a newsroom or analysis workflow? Download the CSV with dates, counts, percentiles, and state-tool URLs.

Method & uncertainty

How the report was generated

Start with the verified public GDD release

The report derives every claim from public release 2026-10-16. It contains 33,642 nationwide ZCTA rows; this 50-state report includes 33,565 fresh values. The source release keeps 20 unavailable rows explicit instead of substituting stale station data.

Compute one transparent heat index

For each day from January 1, daily GDD50 is max(0, (Tmax + Tmin) / 2 − 50°F). Daily values are summed. This is an air-temperature-derived index from NOAA stations, not an on-lawn soil-temperature reading.

Use a freshness-aware station chain

Each ZCTA can consider up to 8 nearby candidates. The pipeline uses the nearest station with sufficiently fresh Tmax/Tmin data and falls back when a closer station is stale or incomplete. 7,675 reported ZCTAs used a fallback.

Aggregate ZCTAs without erasing the spread

Census ZCTAs are assigned to the state containing their largest land-area share. State status comes from the median GDD50; the table also reports the 10th–90th percentile range and every ZCTA-level band count.

The GDD bands come from northern Japanese beetle timing. In Alabama, Arizona, Arkansas, California, Florida, Georgia, Louisiana, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, and Texas, heat from January 1 builds long before beetles fly, so the site's ZIP results follow published university Extension months instead. Those states keep their GDD50 percentiles for reference and are left out of the national band counts.

What the model cannot see

Elevation, coast and lake effects, urban heat, shade, snow cover, irrigation, soil moisture and texture, turf condition, beetle species, and local establishment can shift biology. Recent GHCN-Daily records may lag and can later be replaced by archive-quality values. A station-based ZCTA estimate is a planning proxy, not a measurement of an individual lawn.

Read the full site methodology

Preventive is not curative

The ingredient and the grub stage still decide the action

Preventive

Plan before a damaging population of small grubs is established

Preventive active ingredients do not share one national date. Michigan State's 2026 guidance places chlorantraniliprole earlier than imidacloprid examples. The modeled band should prompt a label and local-guidance check, not a brand-agnostic application order.

Curative

Treat confirmed, susceptible grubs—not a red map color

Crossing 1,300 GDD50 does not automatically call for trichlorfon or another rescue treatment. Confirm live grubs, species or stage, and actual injury. Late rescue control can be partial once grubs are large.

Primary sources

Research and first-party guidance behind the framing

Ebbenga et al. (2022) Field-validated Japanese beetle adult phenology modeling.
Ohio State Phenology Calendar Adult emergence marker; not a pesticide threshold.
Michigan State Extension (2026) Ingredient-specific preventive and curative timing.
University of Minnesota Extension Life cycle, moisture, diagnosis, and treatment distinctions.
UW–Madison Extension Species-specific white grub management windows.
NOAA NCEI GHCN-Daily Daily station Tmax/Tmin and data-quality context.
U.S. EPA pesticide labels Legally enforceable directions and restrictions.
USDA APHIS Japanese beetle Current U.S. distribution context and western limits.

From national signal to local check

Move from the national signal to your ZIP.

This stable report URL follows the latest verified daily release. The ZIP tool shows the current serving value, observation date, and station distance for a specific location.

Check your ZIP's live grub timing