Fall Beekeeping Checklist: September-November Tasks to Winterize Your Hive

A complete fall beekeeping checklist has six tasks: test and treat for varroa in early September, confirm the queen is laying winter bees by mid-September, verify 50-60 lbs of honey stores by the end of September, install a moisture quilt and reduce the entrance in October, switch to dry feed and place a sugar board in November, and stop full inspections once daytime highs drop below 55 F. Miss any of these on schedule and the hive's odds drop fast.

Winter colony losses in the United States hit 55.6% between April 2024 and April 2025 -- the worst annual decline on record (Auburn University / Apiary Inspectors of America, 2025). The University of California Agriculture and Natural Resources (UC ANR) Apiculture Program identifies the fall window -- September through November -- as the single most important management period of the year (UC ANR, 2025).

This guide is a month-by-month autumn hive management checklist calibrated for Northern California frost dates and the Sacramento Valley's almond-bloom calendar. Timing shifts a few weeks earlier in the Sierra foothills and a few weeks later in the Delta, but the sequence is the same.

TL;DR: September is varroa treatment plus store assessment. October is physical winterization -- moisture quilt, reduced entrance, mouse guard, queen excluder removed, wind protection. November is final dry feed plus sugar boards, and the last window to confirm a laying queen. Stop full inspections once consistent highs drop below 55 F. In Northern California, that means mid-September mite treatment, early-October moisture setup, and hands-off by Thanksgiving.

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Why the Fall Window Decides Winter Survival

Fall is not cleanup. Fall is when the biology that decides winter survival actually happens.

Honey bees raised between early September and late October are physiologically different from summer bees. They have larger fat bodies, higher vitellogenin levels, and lifespans of 4-6 months instead of 5-6 weeks (UC Davis Honey Bee Haven, 2025). These "winter bees" or diutinus bees are the colony's entire survival mechanism. Every bee you see clustering in January was raised in September or October.

Three things damage winter bees:

• Varroa mites feed on developing pupae during the exact weeks winter bees are being raised. Parasitized pupae emerge with shortened lifespans, suppressed immunity, and elevated viral loads.
• Nutritional stress reduces fat body development. A colony short on pollen and nectar in early fall produces a smaller, weaker winter-bee cohort.
• Late-season queen failure means fewer winter bees are raised at all. A colony that supersedes in October rarely has time to build a strong cluster before the cold sets in.

Every item on the fall beekeeping checklist below maps to protecting one of those three inputs. Skip fall and you are asking a compromised, under-provisioned colony to survive four months of cold with no reinforcements coming.

see the full winter survival playbook

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The Complete Fall Beekeeping Checklist

September: Treat, Assess, Confirm

September is the most consequential month of the beekeeping year. Three tasks, non-negotiable.

1. Alcohol wash mite test (first week of September)

Pull roughly 300 bees (half a cup) from a brood frame -- not the queen frame -- and use an alcohol wash or sugar roll to count mites. The Honey Bee Health Coalition's treatment threshold is 2-3 mites per 100 bees (Honey Bee Health Coalition, Tools for Varroa Management, 2025). Above threshold means treat immediately.

• Alcohol wash is the most accurate. Kills the sample, but gives a reliable count.
• Sugar roll is non-lethal but undercounts by roughly 25-30%. Acceptable if you are squeamish, but adjust your threshold downward.
• Sticky boards are monitoring only -- they do not produce treatment-grade data.

2. Apply the right treatment for the temperature window

Northern California daytime highs in early September still run 85-95 F in the Sacramento Valley. That rules out some treatments and favors others.

• Formic Pro (formic acid): works from 50-85 F. Use only if you get a cool stretch. In the valley, usually too hot until late September.
• Apiguard (thymol): needs 60-105 F to vaporize. Works most of September in NorCal.
• Apivar (amitraz strips): 6-week treatment, no temperature cap. Widely used, but amitraz resistance is now documented in collapsed colonies nationwide (Honey Bee Health Coalition, 2025) -- rotate, do not rely on it year after year.
• Oxalic acid vaporization: most effective in the broodless winter window, not September. Save it for December-January.

3. Confirm the queen is laying winter bees

By mid-September, you should see eggs, young larvae, and a consistent brood pattern on 3-5 frames. A queenless or poorly mated queen in September is an emergency. Requeen immediately (if mated queens are available from NorCal breeders) or combine with a queenright hive using the newspaper method.

4. Assess honey stores before the end of the month

The Northern California target is 50-60 lbs of capped honey going into October. A full deep Langstroth frame holds 6-8 lbs; a full medium frame holds 4-5 lbs. Heft the hive and count capped frames.

If the colony is light, start feeding 2:1 sugar syrup (two parts granulated sugar to one part water by weight) through a top or frame feeder. Bees can still process heavy syrup while daytime highs stay above 60 F. UC ANR Apiculture notes that colonies receiving fall syrup feeding show meaningfully lower winter loss rates than unfed hives.

5. Remove honey supers

Any honey above a queen excluder or supered for harvest comes off now. Pull supers before mite treatment starts -- most treatments are not label-legal with honey supers on.

deep dive on varroa timing

October: Winterize the Hive

October is physical preparation. The colony is largely done raising brood, winter bees are emerging, and the hive needs to be configured to survive cold, wind, and moisture for four months.

1. Install a moisture quilt or ventilation board

This is the single most overlooked fall task. A wintering cluster emits 3-10 grams of water vapor per hour. That moisture rises, hits a cold inner cover, condenses, and drips back onto the bees. Cold water on a cluster in January kills.

A moisture quilt -- a shallow box filled with wood shavings or burlap, topped with a screened vent -- absorbs rising moisture and lets it escape. Cheap, easy, and arguably the highest-ROI fall purchase.

2. Reduce the entrance to 3-4 inches

A full-width summer entrance is an invitation for robbers, mice, and cold drafts. A reducer strip with a 3-4 inch opening is enough for guard bees to defend and lets the colony manage airflow.

3. Install a mouse guard

A metal strip with 3/8-inch holes lets bees pass but blocks mice. Field mice move into hives in October looking for a warm place to overwinter. A mouse nest at the bottom of a hive is a colony ender.

4. Remove the queen excluder

If you left an excluder between the brood box and a food super, pull it now. The cluster moves upward as it consumes stores. A trapped queen freezes below the cluster. This is one of the most common fall oversights -- check it twice.

5. Strap the hive and add a windbreak

A ratchet strap across the top of the hive keeps the cover on during winter storms. Sacramento Valley winters bring 30-50 mph gusts during atmospheric rivers. A $6 strap is cheap insurance.

If the hive sits exposed to north or west wind, position a windbreak 2-3 feet away -- straw bales, a plywood panel, or a fence section. You do not want the windbreak touching the hive (creates condensation), just blocking direct wind.

6. Prop the bottom board for airflow

Screened bottom boards: remove the insert in mild-winter NorCal climates. Solid bottom boards: prop the front edge up slightly (a popsicle stick works) so moisture can drain out.

7. Do not wrap or insulate in Northern California

Wrapping traps moisture. In the Sacramento Valley and foothills, average winter lows rarely drop below 25 F. Healthy colonies handle that easily if they are dry. Cold and dry beats warm and wet -- every time.

see the hive inspection checklist

November: Final Feeding and Hands-Off Transition

November is your last window to add weight, confirm the queen, and transition the colony into hands-off mode.

1. Switch from syrup to dry feed once highs drop below 50 F

Bees cannot dehydrate and store liquid syrup in cold weather. Once daytime highs stay below 50 F consistently (typically mid-November in NorCal), switch to:

• Fondant patties: soft, ready-to-eat sugar. Place directly on the top bars.
• Sugar bricks or sugar boards: harder sugar slab on top of the frames on a sheet of newspaper. Doubles as a moisture absorber.
• Dry granulated sugar: poured on newspaper above the frames (the "mountain camp" method). Simple and cheap.

2. Final hive weight assessment

Heft the hive one more time before Thanksgiving. If it still feels light, add as much dry sugar as the hive will accommodate. A 5-10 lb sugar board provides 2-4 weeks of emergency feed.

3. Confirm the queen is still present

A brief top-box check on a warm afternoon (above 55 F) is acceptable. Look for a tight cluster on brood frames and a few capped cells of late-season brood. Do not pull frames unless necessary -- breaking the propolis seal disrupts thermoregulation.

4. Stop full inspections

Once daytime highs drop below 55 F consistently, close the hive. Breaking the seal below that temperature chills the cluster and wastes heat the colony spent days generating.

5. Document what you did

Write down the treatment used, the mite count, the final hive weight, and any queen notes. Spring you will thank fall you for the records.

fall nectar flow timing

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Fall Timing by Region: Northern California vs. Colder Climates

Northern California's mild winters shift the fall checklist timing earlier than most beekeeping guides suggest.

Region	First Frost	Mite Treatment Start	Moisture Quilt On	Hands-Off Date
Sacramento Valley	Late November-December	Early September	Mid-October	Late November
Sierra Foothills (1,500-3,500 ft)	Late October-November	Mid-August	Early October	Early November
Coastal (Sonoma, Marin)	Rare/none	Mid-September	Late October	Early December
Pacific Northwest	Late October	Early August	Late September	Late October
Midwest/Northeast	Early-Mid October	Late July-Early August	Mid-September	Mid-October

The rule of thumb: start mite treatment 6-8 weeks before first frost. Have moisture ventilation installed 2-3 weeks before first frost. Stop full inspections once highs drop below 55 F.

Almond bloom in the Central Valley typically starts the third week of February. A colony that comes through fall properly provisioned and mite-free will be ready to build up for almond pollination or your own spring splits.

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The Four Most Common Fall Mistakes

These are the fall errors that show up in winter-loss autopsies, pulled from UC ANR extension reports and Honey Bee Health Coalition case studies.

1. Treating for varroa too late

"I treated in October" is the most common refrain from beekeepers who lost colonies. By October, winter bees have already been parasitized during their pupal stage. The damage is done. Treatment windows close in early-to-mid September for a reason.

2. Over-insulating and under-ventilating

Wrapping the hive feels protective. It is not. Moisture has to go somewhere, and if the top is sealed, it condenses on the inner cover and rains back down on the cluster. In NorCal, skip the wrap entirely. In colder climates, pair any insulation with aggressive upper ventilation.

3. Leaving the queen excluder in place

A queen excluder is a queen-freezer in winter. The cluster moves upward to follow consumed stores. An excluder between boxes traps the queen below the cluster. She dies. So does the colony, because late-fall requeening is rarely possible.

4. Skipping the final weight check

Beekeepers feed in September, get busy in October, and never heft the hive again before December. Then they find a starved-out cluster in February -- inches from uncapped stores the cluster could not reach. Late-November hefting plus a sugar board on top is the fix.

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Quick-Reference Fall Beekeeping Checklist

Print this and tape it inside your hive-tool box.

September

• Alcohol wash mite test (target: below 2-3 mites per 100 bees)
• Apply appropriate varroa treatment for the temperature window
• Confirm laying queen and winter-bee production
• Assess honey stores (target: 50-60 lbs in NorCal)
• Feed 2:1 syrup if stores are light
• Remove honey supers

October

• Install moisture quilt or ventilation board
• Reduce entrance to 3-4 inches
• Install mouse guard
• Remove queen excluder
• Strap hive top cover
• Position windbreak if exposed
• Prop bottom board for airflow
• Skip wrapping in NorCal

November

• Switch from syrup to dry feed
• Final hefted weight assessment
• Add sugar board on top of frames
• Confirm queen on a warm-afternoon check
• Stop full inspections once highs stay below 55 F
• Document treatment, weights, and queen status

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Frequently Asked Questions

What to do with bees in fall?

Fall beekeeping tasks are varroa treatment, honey store assessment, and physical winterization -- in that order. In September, test mite loads with an alcohol wash and treat if above 2-3 mites per 100 bees. Confirm the queen is laying winter bees and that the colony has 50-60 lbs of capped honey. In October, install a moisture quilt, reduce the entrance, add a mouse guard, remove the queen excluder, and strap the hive. In November, switch to dry feed, add a sugar board, and stop opening the hive once daytime highs drop below 55 F.

When to winterize a beehive?

Physical winterization (moisture quilt, entrance reducer, mouse guard, wind protection) should be complete 2-3 weeks before the average first frost. In the Sacramento Valley that means mid-October. In the Sierra foothills, early October. In the Pacific Northwest or upper Midwest, mid-September. Varroa treatment runs earlier -- start 6-8 weeks before first frost so winter bees are raised with minimal mite pressure.

How do I prepare bees for winter in California?

Preparing bees for winter in California starts in early September with an alcohol wash mite test and treatment if needed. Verify 50-60 lbs of honey stores by late September and feed 2:1 syrup if the colony is light. In October, install a moisture quilt, reduce the entrance, add a mouse guard, remove the queen excluder, and strap the cover. Skip insulation wraps -- California winters are mild enough that trapped moisture is a bigger risk than cold. In November, switch to dry feed (fondant or sugar boards) and stop full inspections once daytime highs stay below 55 F. Expect almond bloom around the third week of February in the Central Valley.

When should I stop inspecting hives in fall?

Stop full frame-by-frame inspections once consistent daytime highs drop below 55 F. In Northern California that is typically mid-to-late November. Below 55 F, bees cannot re-seal the propolis gaps you break when you open the hive, and the cluster has to waste energy re-warming chilled brood or bees. Quick top-box checks (cracking the inner cover to place fondant, for example) are acceptable on warm afternoons. Full inspections resume in February when you see the first 55-60 F days in the Sacramento Valley.

How late can I treat for varroa mites?

Varroa treatment should be complete before winter bees emerge -- which means the treatment window effectively closes by mid-to-late September in Northern California. Formic acid (Formic Pro) and thymol (Apiguard) both need brood in the hive to be effective, which rules out late-fall application. Oxalic acid vaporization is the exception: it is most effective in the broodless December-January window and catches mites that survived the fall treatment. If you miss the September window, you are banking on a broodless OA treatment in midwinter and accepting higher winter-loss risk.

Do I need to feed my bees in fall?

Feed in fall only if honey stores are below target. The target for Northern California is 50-60 lbs of capped honey; colder regions need 60-80 lbs. Heft the hive and count capped frames in September. If stores are light, feed 2:1 sugar syrup through a top or frame feeder while daytime highs stay above 60 F. Once highs drop below 50 F, switch to dry feed -- fondant, sugar bricks, or the mountain-camp method with granulated sugar on newspaper above the frames.

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Spring Starts with a September Mite Test

Fall beekeeping is not about what you do in October. It is about what you did in the first week of September -- and whether you followed through in October and November.

The colonies that reach almond bloom in February alive are the ones whose beekeepers treated for varroa before winter bees emerged, verified stores before the last warm feeding days, installed moisture ventilation before the first storm, and stopped opening the hive before the cluster needed its propolis seal intact.

The 55.6% national loss rate is not inevitable. It is the average across beekeepers who did and did not follow a fall checklist. Do the six September tasks, the seven October tasks, and the five November tasks above, and your colony has every structural reason to be alive when the first almond blossoms open.

Ready to keep going? See the month-by-month first-winter survival protocol, dial in your varroa treatment timing, plan supplemental feeding with the honey bee nutrition guide, or map your region's bloom calendar with the Northern California nectar flow calendar.