National field report August 29, 2026

The largest current group is closing: 95% of covered U.S. ZCTAs.

The latest verified release places 31,903 of 33,565 covered ZCTAs in the modeled preventive window closing band. The report rebuilds daily from the same citable GDD release used by the public data product.

Check your ZIP's live status See all 50 states

The national pulse

The current distribution across four modeled timing bands

Below 800 GDD50

1.8%

Too early

596 ZCTAs

800–1,000 GDD50

0.9%

Approaching

308 ZCTAs

>1,000–1,300 GDD50

2.3%

Open

758 ZCTAs

Above 1,300 GDD50

95%

Closing

31,903 ZCTAs

National median 2,753.4 GDD50

The midpoint covered ZCTA is preventive window closing.

Geographic spread 1,651.8–4,926.1

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

Station fallback 5,942 ZCTAs

Used a fresher alternate station in public release 2026-08-29.

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. 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 2,073.1 GDD50; 4.8% open, 0% approaching, and 94% closing across 992 covered ZCTAs.

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Closing

Ohio

Median 2,534.1 GDD50; 0% open, 0% approaching, and 100% closing across 1,233 covered ZCTAs.

Open Ohio's ZIP tool

Closing

Wisconsin

Median 2,064.6 GDD50; 0.6% open, 0.9% approaching, and 98.5% closing across 783 covered ZCTAs.

Open Wisconsin's ZIP tool

Closing

Minnesota

Median 2,083.4 GDD50; 4.3% open, 0.3% approaching, and 94.9% closing across 880 covered ZCTAs.

Open Minnesota's ZIP tool

Closing

New York

Median 1,996.7 GDD50; 1.8% open, 0% approaching, and 97.3% closing across 1,826 covered ZCTAs.

Open New York's ZIP tool

Closing

Massachusetts

Median 2,115.3 GDD50; 2.8% open, 1.5% approaching, and 95.7% closing across 539 covered ZCTAs.

Open Massachusetts's ZIP tool

Closing

Connecticut

Median 2,128.2 GDD50; 0% open, 0% approaching, and 100% closing across 288 covered ZCTAs.

Open Connecticut's ZIP tool

Closing

Maine

Median 1,763.5 GDD50; 5.6% open, 1.9% approaching, and 92.3% closing across 427 covered ZCTAs.

Open Maine's ZIP tool

Closing

North Dakota

Median 1,834.2 GDD50; 9% open, 0% approaching, and 85.1% closing across 389 covered ZCTAs.

Open North Dakota's ZIP tool

Closing

Oregon

Median 1,797.8 GDD50; 15% open, 4% approaching, and 77.3% closing across 428 covered ZCTAs.

Open Oregon's ZIP tool

Closing

Washington

Median 1,644.3 GDD50; 14.2% open, 5.1% approaching, and 76% closing across 605 covered ZCTAs.

Open Washington's ZIP tool

Closing

Colorado

Median 2,290.8 GDD50; 5.9% open, 4.7% approaching, and 77.3% 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 August 29, 2026
State	Median GDD50	10th–90th pct.	Modeled status	Too early	Approaching	Open	Closing	Available ZCTAs
Alabama AL	4,410.8	3,317.9–4,866	Closing	0	0	0	656	656
Alaska AK	393.3	111.8–782.3	Too early	228	17	0	0	245
Arizona AZ	5,428.8	2,309.6–7,257	Closing	1	0	2	413	416
Arkansas AR	4,069.8	3,017.2–4,647.4	Closing	0	0	7	607	614
California CA	3,685.9	2,145.2–4,609.8	Closing	11	17	29	1,746	1,803
Colorado CO	2,290.8	733.8–3,090.4	Closing	64	25	31	408	528
Connecticut CT	2,128.2	1,755.5–2,509.6	Closing	0	0	0	288	288
Delaware DE	3,173.9	3,083–3,278.7	Closing	0	0	0	68	68
Florida FL	5,628.1	4,828–6,361	Closing	0	0	0	1,013	1,013
Georgia GA	4,154.3	3,352.6–4,930.5	Closing	12	0	0	739	751
Hawaii HI	5,208.7	1,849.1–6,422.1	Closing	2	0	8	87	97
Idaho ID	1,761.9	1,020.4–2,633	Closing	13	14	33	220	280
Illinois IL	2,795.7	2,385.9–3,419.9	Closing	14	4	0	1,378	1,396
Indiana IN	2,675.7	2,239.9–3,255.3	Closing	0	0	0	807	807
Iowa IA	2,496.3	2,083–2,867.9	Closing	0	0	8	962	970
Kansas KS	3,416.8	2,916.4–3,897.5	Closing	0	0	7	697	704
Kentucky KY	3,186.7	2,144.5–3,699.7	Closing	2	0	12	765	779
Louisiana LA	5,260.9	4,491.4–5,436.2	Closing	0	0	0	539	539
Maine ME	1,763.5	1,363.6–1,992.9	Closing	1	8	24	394	427
Maryland MD	3,064.3	2,541.3–3,517.6	Closing	0	0	8	469	477
Massachusetts MA	2,115.3	1,811.1–2,458.4	Closing	0	8	15	516	539
Michigan MI	2,073.1	1,388.1–2,358.3	Closing	12	0	48	932	992
Minnesota MN	2,083.4	1,405.6–2,411.1	Closing	4	3	38	835	880
Mississippi MS	4,658.4	3,646.5–5,158	Closing	0	0	0	427	427
Missouri MO	3,283.9	2,755.4–3,700.4	Closing	0	0	11	1,024	1,035
Montana MT	1,538.3	765.3–2,217.7	Closing	45	27	53	244	369
Nebraska NE	2,741.4	2,270.4–3,071	Closing	0	0	0	586	586
Nevada NV	3,016.1	1,189.7–6,246.9	Closing	4	7	11	158	180
New Hampshire NH	1,904.3	729.3–2,141.8	Closing	27	1	15	203	246
New Jersey NJ	2,820.6	2,439.4–3,083	Closing	0	0	0	598	598
New Mexico NM	2,528.8	915.2–4,306.1	Closing	23	18	33	299	373
New York NY	1,996.7	1,597.9–2,872.1	Closing	16	0	33	1,777	1,826
North Carolina NC	3,699.2	2,440.6–4,173.8	Closing	5	0	11	837	853
North Dakota ND	1,834.2	1,055.6–2,110.8	Closing	23	0	35	331	389
Ohio OH	2,534.1	2,151.8–2,970	Closing	0	0	0	1,233	1,233
Oklahoma OK	4,496.5	3,728.6–4,758.2	Closing	0	0	0	644	644
Oregon OR	1,797.8	1,047.1–2,418.5	Closing	16	17	64	331	428
Pennsylvania PA	2,290.2	1,761.3–2,888.7	Closing	0	11	38	1,784	1,833
Rhode Island RI	2,196.6	1,948.2–2,421.4	Closing	0	0	0	81	81
South Carolina SC	4,124.8	3,409.2–4,756.7	Closing	2	0	0	422	424
South Dakota SD	2,249.3	1,837.5–2,613.1	Closing	1	1	1	372	375
Tennessee TN	3,604.1	2,645.5–4,167.8	Closing	8	2	0	628	638
Texas TX	5,304.2	4,288.8–5,865	Closing	0	0	0	1,989	1,989
Utah UT	2,268.7	1,011.8–3,349.7	Closing	13	16	36	234	299
Vermont VT	1,601.9	1,157.9–1,982.5	Closing	0	20	21	224	265
Virginia VA	3,212.2	2,292.8–3,659.4	Closing	0	19	6	878	903
Washington WA	1,644.3	1,034.9–2,355.7	Closing	28	31	86	460	605
West Virginia WV	2,521	1,820.6–3,108.6	Closing	0	16	2	720	738
Wisconsin WI	2,064.6	1,628.9–2,355.8	Closing	0	7	5	771	783
Wyoming WY	1,852.4	743.3–2,399.2	Closing	21	19	27	109	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 2026-08-29. 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. 5,942 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.

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