Every year when the Camellias start to bloom I remember learning about a devastating occurrence of “pollen-poison” while taking a commercial chemical safety class in the early 2000’s.
They told us of a small city on the west coast that started noticing an large amount of dead bees during the fall when the camellias were blooming. In an effort to solve the mystery, they discovered that the local municipality, in an effort to control tea scale, sprayed all of their Camellias lining a city street with a systemic insecticide. What concerned them was that the application was made months prior to blooming so damage was not anticipated. They assumed incorrectly that the insecticide would only be in the plants for a short period. After investigation it was determined that the massive bee loss was pollen poison from the Camellia that did not dicipate as they were told by the chemical companies.
But it’s not just Camellias that systemics are used on. I see folks suggesting systemic insecticides on Citrus, Crape Myrtle, and just about anything else that is deemed a problem with insects.
Bees and other pollinators are the lifeblood of a healthy garden. They pollinate the plants that feed, shelter, and inspire us. But in trying to protect those same plants from pests, we sometimes use products that harm the very creatures we depend on most.
One of the least visible — yet most damaging — threats is pollen poisoning, which happens when systemic insecticides move inside the plant and contaminate its pollen and nectar. When bees and other pollinators visit those flowers, they’re exposed to toxic residues that can weaken or kill them.
What Does “Systemic” Mean?
A systemic chemical doesn’t stay on the leaf surface — it’s absorbed through the roots, stems, or leaves and circulates throughout the entire plant
That means the chemical becomes part of the plant’s tissues, including its pollen, nectar and fruit. When bees, butterflies, and other pollinators visit those flowers, they’re feeding directly on a chemically contaminated food source.
Even when used carefully, systemic products can remain active in the soil and be taken up by new growth months later. So how long does the chemical stay in the plant? That’s the million dollar question. Are you sure enough that it’s all gone before blooming that you’re willing to run the risk?
How Pollen Poisoning Happens
Systemic chemicals, including insecticides and fungicides, move throughout a plant’s vascular system, protecting it from the inside out. When that plant blooms, traces of the chemical can appear in its pollen, nector and yes…fruit.
Bees and other pollinators collecting those food sources ingest the contaminated material and carry it back to their colonies or nests. Over time, exposure can cause disorientation, reduced reproduction, weakened immunity, or death — a phenomenon now recognized as pollen poisoning.
But what about your own food, fruits and vegetables that could be contaminated by systemic insecticides. Leafy plants, citrus, fruit, vegetables and other food could carry that poison right to your mouth. Are you 100% sure it cant? I’m certainly not.
This concern is not just from ‘tree huggers’ ‘pro-organic consumers’ and ‘no chemical advocates’ It is a very real concern in the landscape and bee keepers industries.
The UGA Pest Management Handbook states : “NOTE: There is increasing concern about the health of pollinator populations, especially honeybees and other bees. Flowering plants in the landscape, including flowering weeds and wildflowers, are important sources of food for these very beneficial insects. Care should be taken when using insecticides around any flowering plants when bees are actively foraging. Under some circumstances, systemic insecticides like imidacloprid and dinotefuran may be translocated to the blooms and picked up in nectar and pollen. Avoid spraying turf when flowering weeds or clover are in bloom. Mowing to remove the blooms before treating will greatly reduce risks associated with these materials. Follow all label directions carefully.” Source
Common Chemicals of Concern
Imidacloprid
- Type: Neonicotinoid — a widely used systemic insecticide.
- How it works: Absorbed into the plant and distributed through sap, pollen, and nectar.
- Effect on pollinators: Disrupts nerve signaling, causing paralysis, disorientation, and loss of navigation.
- Research findings: Studies show that even low-level imidacloprid exposure reduces honey bee survival and alters gene expression.
Disulfoton
- Type: Organophosphate — both contact and systemic in action.
- How it works: Penetrates plant tissues and remains toxic on leaves and flowers long after application.
- Risk: Highly toxic to bees through contact or ingestion. Listed by Oregon State University Extension as incompatible with pollinators when applied to blooming plants.
Acephate
- Type: Systemic organophosphate insecticide.
- How it works: Moves through the plant’s system and breaks down into methamidophos, an even more toxic compound.
- Effect: Found in pollen and nectar of treated plants; can cause disorientation, reduced foraging, and colony decline in bees.
- Common uses: Turf, ornamental shrubs, and landscape plants — areas frequently visited by pollinators.
Why Pollen Poisoning Matters
Bees and other pollinators are responsible for nearly one-third of our food supply and are vital to both wild and cultivated ecosystems. When their health declines, so does plant diversity, crop yield, and environmental balance.
Systemic pesticides and fungicides make this issue especially concerning because contamination isn’t limited to direct spray exposure. Even plants treated weeks or months before bloom can produce toxic pollen and nectar that harm visiting bees and other pollinators.
Sub-lethal exposure — where pollinators don’t die immediately but are gradually weakened — is a major factor in reduced hive health and population decline.
Blackcreek Nursery does not use systemic chemicals on our plants or at our facility and we discourage the use of them all together in order to protect our valuable pollinator resource.
Safer Steps for Gardeners
Protecting bees and other pollinators starts with small, mindful changes in how we manage our gardens and landscapes.
- READ THE LABEL The largest danger to pollinators is the careless human. Just like us, when we are given an RX, we learn the side effects of the medication. Insecticides are no different. Know what you’re doing and why before you grab a chemical. Don’t just take a manufacturer’s or retailer’s recommendation. Read about the dangers of the chemical you are applying before you do it, and get a second opinion if necessary.
- Avoid all insecticide use on blooming plants. Never spray when flowers are open or when bees are active. This applies to non-systemics as well. Even organics like Neem can harm beneficial insects if you spray it where they will come in contact with it.
- If treatment is necessary, apply at dusk or dawn. Pollinators are less active during those hours.
- Choose natural or low-risk alternatives. Horticultural oils, insecticidal soaps, and neem oil can control many pests safely.
- Build pollinator-safe zones. Plant unsprayed flowering strips or native plants to give bees and butterflies clean food sources.
- Look for warnings such as “Toxic to bees” or bee protection icons, and follow all restrictions.
- Educate others. Share pollinator-friendly practices with neighbors, community gardens, and local schools.
- Use your brain and your intuition. If something doesn’t sound or feel right, it probably is not.
A Healthier Garden for All
Our gardens thrive when bees and other pollinators thrive. By choosing safer pest-control options and avoiding systemic insecticides that linger in plant tissues, we protect not only the beauty of our plants but the future of the ecosystems that sustain them.
Healthy soil, healthy plants, and healthy pollinators are all connected — and as gardeners, we have the power to nurture that balance.
Want to explore the research behind this article? Visit our Pollinator Protection Resources page for university studies and extension guides.
