Oak wilt: what each state and province agency says about pruning months

This page reports what the official source says. It is not legal advice: ask the office named here. Oak wilt is a fungal disease of oaks. The pages below come from forestry, natural resources and food inspection agencies that publish a page on it. The months differ from agency to agency, and each row gives the agency's own dates. The main write-up of the disease is on the oak wilt disease page, and the wider list of tree diseases is in tree diseases: what the agencies record.

The table

Place and agency	Does the page report oak wilt there	What the page says about months
Wisconsin Department of Natural Resources, oak wilt page	Yes. It says oak wilt is widespread in southern Wisconsin and, in much of northern Wisconsin, a new and uncommon disease. Its detection map is dated January 21, 2026.	The greatest risk of spread is April through July. If oaks are pruned between April and July, the page says wound sealer goes on immediately after the cut. For forest harvesting in a county with oak wilt, or within 6 miles of one, the oak harvesting guidelines give restricted periods of April 15 to July 15 in the North Zone and April 1 to July 15 in the South Zone.
Minnesota Department of Natural Resources, oak wilt page and news release of April 6, 2026	Yes. The page says it was first found there around 1945 and is widespread in east-central and southeast Minnesota. The release says the department has confirmed it in 31 counties and that no new counties were confirmed in 2025.	The release calls not pruning or cutting oaks from April through July the simplest way to curb spread, and says the risk of wound infection drops after mid-July.
Iowa Department of Natural Resources, oak wilt page	The page does not say where in Iowa oak wilt has been found.	A risk table on the page gives High Risk as March 15 to August 1, Low Risk as August 2 to October 31, and the Safest Trimming Period as November 1 to March 14.
New York Department of Environmental Conservation, oak wilt page	Yes. First detected in the state in 2008. The page lists active infection centers as of October 2025 in Monroe, Ontario and Yates counties, and says it was confirmed in the Town of Greece in July 2026. It describes one active quarantine district, in the Finger Lakes region.	The page says to avoid pruning or wounding oaks in March to September, when spore mats are present and beetles are most active, and says a wound made in spring or summer should be sealed immediately.
Texas Texas A&M Forest Service, news release of February 5, 2026	Yes. The 2026 release says oak wilt has killed millions of trees across Central Texas and names the Hill Country. It lists no counties. The 2025 release says it is killing millions of trees across 76 Texas counties.	The February 5, 2026 release calls avoiding oak pruning from February 1 through June 30 critical, and says any necessary pruning cuts must be painted at once. A release of February 4, 2025 gives the same advice as February through June and says all oak wounds should be painted immediately in any month.
Michigan Department of Natural Resources, news bulletin of April 14, 2023	Yes. The bulletin dates the first confirmation in Michigan to the early 1950s, calls it common in the Lower Peninsula, and names Menominee, Dickinson and Iron counties in the Upper Peninsula.	The bulletin names April 15 to July 15 as the high risk period and says oak trees should not be pruned in it. It says the department restricts cutting of red oak on state land between April 15 and July 15, and recommends private landowners delay oak harvests until after July 15 where possible.
Missouri Department of Conservation, oak wilt page	The page does not say where in Missouri oak wilt has been found. It describes how the disease spreads in the state and says root grafting is less common in Missouri than in some states.	The page lists mid-March through June as the months to avoid pruning or damaging oaks, and says oaks become more susceptible a couple of weeks before budbreak.
South Dakota Department of Agriculture and Natural Resources, Forest Pest Bulletin 101, June 2021	Yes, in a limited way. The bulletin says oak wilt was reported occasionally in Minnehaha County in the 1980s and 1990s, and that there are reports in western South Dakota, though its occurrence there is thought to be relatively rare.	The bulletin lists April, May and June as the months to avoid pruning any oak, because fresh cuts then attract insects that can carry spores.
Pennsylvania Department of Conservation and Natural Resources, insects and diseases page	The page lists oak wilt among the pests that affect the state's forests. It gives no counties.	No official page found on October 8, 2026 that gives months. The insects and diseases page has none.
Nebraska University of Nebraska-Lincoln, ProHort Update for September 2026 (an extension horticulture newsletter, not an agency page)	Yes, one case. The update says a red oak sample from Omaha was sent to the Nebraska Forest Service, which sent samples on to Iowa State, and the tree tested positive.	The update says pruning is done between Halloween and Valentine's Day (October 31 to February 14), maybe to St. Patrick's Day, and that different literature gives different time frames. It says a pruning sealant goes on after the cut if pruning falls outside those dates. No official page found on October 8, 2026 from the Nebraska Forest Service itself.
Ontario Province of Ontario, oak wilt page, updated September 7, 2023	Yes. It says oak wilt was found in Canada for the first time in 2023 in the Niagara Falls area, and was also detected in the Township of Springwater and in Niagara-on-the-Lake.	The page names April through July as the high risk period for pruning or wounding oaks, and says ideally none is done between April and November.
Canada, federal Canadian Food Inspection Agency, oak wilt page, modified January 11, 2024	Yes. It names the City of Niagara Falls (the first confirmed detection in Canada), the Township of Springwater and the Town of Niagara-on-the-Lake, all in Ontario.	The page lists "Don't prune oak trees between April and November". It says the agency may issue a Notice of Prohibition of Movement or a Notice to Dispose to affected property owners.

What the pages share

All of the pages above link oak wilt to sap-feeding beetles that carry spores to fresh wounds. Wisconsin and New York also describe spread underground through grafted roots. Minnesota and Wisconsin say the red oak group dies faster than the white oak group. For the symptoms, look-alikes and lab confirmation lines each agency gives, see the oak wilt disease page.

Reading the months

The dates are not the same in each place. Wisconsin and Minnesota say April through July. Michigan says April 15 to July 15. Missouri says mid-March through June, and South Dakota says April, May and June. Texas gives February 1 through June 30 in one release and February through June in another. Iowa gives March 15 to August 1 as high risk. New York says March to September, and Ontario and the federal agency say April to November. Each agency ties its dates to local beetle activity or to local detections. Wisconsin's page says municipalities may have their own oak wilt ordinances and that an electric utility pruning rule sits in the Wisconsin Administrative Code, PSC 113.0511. For who to report to, see the United States report-a-pest guide and the Canada report-a-pest guide.

Oak wilt: what each state and province agency says about pruning months

The table

What the pages share

Reading the months

Sources