Safety and the community
Bees and pesticides: how aerial applicators protect pollinators
By the Sutter Butte Dusters team · · 8 min read
Bees and pesticides meet every year in the northern Sacramento Valley, most of all when beekeepers set hives in almond orchards for bloom. The same orchards can need a fungicide or an insecticide at the same time. This post explains how bees get exposed, what the label and California law require, and how an aerial applicator (crop duster) protects the hives.
Why do bees and pesticides matter so much in Sacramento Valley orchards?
Almond growers rent honey bee colonies for pollination, because almonds need bees to set a crop. In the northern Sacramento Valley, almond bloom usually comes in February. Bees also visit other blooming crops, and blooming weeds along roads and ditches.
Bees do not stay in one orchard. The Almond Board of California notes that bees can forage up to 4 miles away. A hive at the edge of one block can visit the crops of several neighbors.
Exposure happens in these main ways:
- A pesticide that is toxic to bees goes onto a crop in bloom.
- Spray drifts onto a blooming crop, a hedgerow or blooming weeds next to the field.
- Spray lands on blooming ground cover under the trees.
- Foragers carry residue on pollen or nectar back to the colony, where it can affect the brood (the young bees).
- Bees drink from puddles or dew on treated leaves.
- Spray droplets hit flying bees and weigh down their wings, as the Almond Board warns.
Which pesticides are most toxic to bees?
Insecticides carry the greatest risk to bees, because their purpose is to kill insects. Other products and mixes can also cause harm. The Almond Board reports bee losses after growers tank mixed an insecticide with a bloom fungicide. University of California advice is to add no adjuvant (spray additive) to a bloom fungicide unless the label says to.
The University of California Statewide IPM Program gives each active ingredient a bee rating. You can search the UC IPM Bee Precaution Pesticide Ratings by the common name of the active ingredient. The table summarizes each rating.
| UC IPM rating | Toxicity to adult honey bees | What UC IPM advises |
|---|---|---|
| I | High toxicity, or extended residual toxicity | Avoid application or drift onto flowering plants, including weeds, and onto water that bees can reach. |
| II | Moderate toxicity, without extended residual toxicity | Avoid application or drift onto flowering plants, except between sunset and midnight if the label allows it. |
| III | Low toxicity | No bee precaution, except what the label or regulations require. |
UC IPM states that its ratings are not the label statements. A rating can advise against a timing that the label allows, such as an application during bloom.
California adds its own limits for one insecticide class. Since January 1, 2024, Title 3, California Code of Regulations, sections 6990 through 6990.16 limit neonicotinoid use on most food and feed crops. The rules cover clothianidin, dinotefuran, imidacloprid and thiamethoxam. The California Department of Pesticide Regulation (DPR) fact sheet for tree nut crops states that the rules prohibit an application during almond and walnut bloom. Product labels do not show these limits.
The licensed pest control adviser (PCA) chooses the product. The applicator follows that written recommendation and the label.
How do you read a pesticide label for pollinator protection?
The label is the law for each pesticide. In California, a pesticide is "toxic to bees" when its labeling includes those words. That definition is in Title 3, section 6980.
Before a job near bees, check these parts of the label:
- Environmental Hazards statement. This section states whether the product is toxic to bees.
- Directions for Use. This section can prohibit an application to a crop in bloom, or allow it only when bees are not active.
- Residual toxicity (RT) time. RT time is the period after an application until the product has minimal toxic effect on bees.
- Adjuvant and drift statements. These set the allowed additives, wind limits and buffer distances.
A label can be stricter than state law. When the label and a regulation differ, follow the stricter rule.
When are bees inactive under California rules?
Under Title 3, section 6980, bees are inactive from one hour after sunset to two hours before sunrise. Bees are also inactive when the temperature is below 50 degrees Fahrenheit.
The temperature limit was 55 degrees until January 1, 2022. That day, DPR lowered it to 50 degrees. The same rule change renumbered the bee sections of Title 3 as sections 6980 through 6984.
Timing alone does not settle every conflict between bees and pesticides. A product with a long RT time can stay toxic into the next morning. Dew can also wet the residue again. For almond bloom, the Almond Board advises that a necessary fungicide go on in the late afternoon or evening. The spray also needs time to dry before the bees fly the next day.
What are the beekeeper notification pesticide rules in California?
California law gives registered beekeepers a right to advance notice. Each beekeeper registers each apiary (bee yard) with the county agricultural commissioner and asks for notification at the same time. Under Title 3, section 6982, that request ends on December 31 of each year.
The applicator also has a duty under Title 3, section 6983. Before an application of a pesticide labeled toxic to bees to a blossoming plant, the applicator asks the commissioner about nearby apiaries. The search covers each apiary within 1 mile whose operator requested notification.
If a beekeeper asked for notice, the applicator must give it at least 48 hours before the application. The notice must include these five items:
- The time and place of the application.
- The crop and the number of acres.
- The method of application, for example by air.
- The active ingredients and the dosage rate.
- How the beekeeper can contact the applicator.
The commissioner can change the 48-hour period. The beekeeper and the applicator can also change it by agreement.
BeeWhere is the statewide online system for apiary registration and notification. On BeeWhere, growers and commercial applicators get contact details for beekeepers with colonies within 1 mile of an upcoming application. Butte, Glenn and Tehama counties had a separate regional notification service with fees, and DPR repealed it effective January 1, 2022.
Use these steps before a bee-toxic application to a blooming crop or blooming weeds:
- Read the bee statements on the label and the PCA recommendation.
- Search BeeWhere or call the county agricultural commissioner.
- List each beekeeper within 1 mile who asked for notice.
- Send each beekeeper the five required items at least 48 hours ahead.
- Record the date, time and method of each notice.
- Contact the beekeepers again if the job moves to a new day.
A beekeeper who moves hives within the same county must also tell the commissioner, and BeeWhere accepts that report.
How does an aerial applicator protect bees during a flight?
Drift control comes first. California regulation 3 CCR 6614 does not allow an application when there is a reasonable possibility of damage to nontarget crops, animals or property. Our post on how spray drift works in aerial application explains wind, droplet size and release height.
Caution: Do not spray a hive, and do not let spray drift onto a hive.
The field map shows each hive location that the grower or beekeeper reports. The pilot plans the passes so that the spray stays off the hives and the field edges where they sit. The pilot shuts off the spray at the end of each pass, before the turn. The Almond Board's eight bloom spray tips also say to turn off the nozzles near hives and to avoid flying bees.
Other practices also lower the risk:
- Treat blooming weeds and cover crops as blooming plants, as the UC IPM ratings do.
- Leave hedgerows and natural areas outside the spray pattern, because native bees live there.
- Ask the grower to cover or remove bee water sources before the job, as the Almond Board advises.
- Wait when the wind blows toward hives or a blooming crop.
Our post on orchard spraying by air covers coverage and timing in tall trees.
What should growers and beekeepers agree on before almond bloom?
The Almond Board advises growers, beekeepers and PCAs to agree ahead of bloom on which pesticides the grower may apply, if a spray becomes necessary. Each person in the chain has a clear job.
| Person | Job before and during bloom |
|---|---|
| Grower | Tells the PCA and the applicator where the hives are and when they arrive and leave. |
| PCA | Writes recommendations that account for bloom, bee ratings and label limits. |
| Beekeeper | Registers each apiary, asks for notification and reports each hive move. |
| Applicator | Checks for apiaries within 1 mile, sends the 48-hour notice and keeps the spray off hives. |
The Almond Board cites a University of California guideline for hive removal. Remove the hives when 90 percent of the latest variety reaches petal fall. Hives that stay after bloom can forage in nearby crops that receive insecticide.
What should you do after a suspected pesticide bee kill?
The Almond Board lists the signs of a pesticide bee kill. Look for large numbers of dead or dying bees in front of the hives. Other signs are dead brood or dead young workers at the entrance, and few or slow foragers in good flight weather.
If you see the signs:
- Take photos of the hives, the dead bees and the nearby fields.
- Write down the date, the time, the wind direction and any spray activity you saw.
- Call the county agricultural commissioner as soon as possible.
- Use 1-87PestLine (1-877-378-5463) if you do not know the county number.
- Ask the commissioner how to collect and store bee samples.
- Tell the investigator about any treatments that you put in the hives.
The commissioner investigates the incident. Our guide to pesticide application rules in California explains the records that applicators keep. Neighbors who keep bees can also read what neighbors should know about crop dusting.
How we protect pollinators in the northern Sacramento Valley
Sutter Butte Dusters flies from 4080 Clark Rd in Live Oak, with five Ag Cats and one Air Tractor 602. We fly orchards and row crops across Sutter, Yuba, Butte, Glenn and Colusa counties, on the schedule in your PCA's recommendation. Before each job, we map the field and check hazards and sensitive areas nearby. Tell us where the hives are and when they arrive, so that the check includes them. Other answers are on our frequently asked questions page. When your orchard needs a flight, get a quote for your field.
Questions
Yes, in some cases. Before a pesticide labeled toxic to bees goes onto a blossoming plant, California requires the applicator to check for apiaries within 1 mile. Each beekeeper there who requested notice must get the details at least 48 hours before the application.
Register each apiary with the agricultural commissioner of the county where the bees are, and ask for notification when you register. The statewide BeeWhere website handles registration and notification. The notification request ends on December 31, so renew it each year, and report each hive move within the county.
California treats bees as inactive from one hour after sunset to two hours before sunrise, or below 50 degrees Fahrenheit. The label still controls. Some products stay toxic into the next morning, so check the residual toxicity time on the label with your PCA.
Not always. The Almond Board reports bee losses after an insecticide was tank mixed with a bloom fungicide. It advises a necessary bloom fungicide in the late afternoon or evening, and University of California advice is to add no adjuvant unless the label calls for one.
