Your Garden Tomatoes and Flowers Could Be Killing Honeybees

Wednesday Sep 18 | BY |
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Your garden plants may be contaminated with a pesticide known to be toxic to honeybees.

For the last several years now, we’ve been hearing about the decline in our honeybee populations. According to the USDA, the total number of managed honeybee colonies has decreased from 5 million in the 1940s to only 2.5 million today. Annual losses from the winter of 2006-2011 averaged about 33 percent each year, with losses of 22 percent in the winter of 2011-2012 alone.

Scientists have been trying to figure out what’s causing the rapid drop-off in honeybee populations. They’ve looked at environmental stressors such as a lack of diversity in nectar and pollen, management stressors like poor nutrition and overcrowding, parasites like mites, and pathogens like fungi. But one potential cause has come to the forefront lately—pesticides.

One particular class of pesticides called “neonicotinoids,”—which includes clothianidin, thiamethoxam, and imidacloprid—has been found to be particularly toxic to honeybees. In 2008, Germany revoked the registration of clothianidin for use on seed corn after an incident that resulted in the die-off of hundreds of nearby colonies.

Just last June near Portland, Oregon, an estimated over 50,000 honeybees died when a contractor sprayed 55 trees with a potent neonicotinoid called “dinotefuran.” The trees were in bloom at the time, and the bees started falling off like rain. The bees killed represented more than 300 wild colonies.

These pesticides are typically used to control industrial crops like corn, but recently, a new study by Friends of the Earth has discovered this same class of pesticides in garden plants like tomatoes, squash, salvia, and flowers.

Could your garden plants be killing off bees without you even knowing it?

What Are Neonicotinoids?

Neonicotinoids are a newer class of insecticides introduced in the 1990s that affect the nervous system of insects. Chemically related to nicotine, they are actually less toxic than other types of insecticides, at least to mammals. Initially, they were thought to be less toxic to beneficial insects as well, but that has come into question lately.

Today, these pesticides have become widely used in commercial farming. What has made neonicotinoids popular is that they’re water-soluble. Though they can be applied to the plant, they can also be applied to the soil and “taken up” into the plants, which helps reduce insecticide drift. This property also makes the insecticide long lasting, providing the plant with its own protection throughout its life.

This very property, however, is what has made these pesticides potentially toxic to honey bees. By taking the pesticide into itself, the plant later “expresses” it through its nectar and pollen—on which the bees later feed. Even at low levels, the pesticide can affect the bee’s ability to forage for nectar or remember how to get back to its hive, and can even dampen its immune system.

According to the Xerces Society for Invertebrate Conservation, “The long-lasting presence of neonicotinoids in plants, although useful from a pest management standpoint, makes is possible for these chemicals to harm pollinators even when the initial application is made outside of the bloom period. In addition, neonicotinoids persist in the soil and in plants for very long periods of time.”

Even untreated plants can absorb chemical residues of neonicotinoids in the soil from the previous year, with residues found in woody plants up to six years after application.

More Potent in House and Garden Plants

What’s particularly disturbing about finding these pesticides in garden plants is that it points to a more widespread contamination than was previously expected. Though neonicotinoids are widely used in crops like corn, canola, and sunflower, it wasn’t expected to be found in common household and gardening plants.

It turns out commercial greenhouses and nurseries commonly treat potting soil and plants with these pesticides before they leave the store. Worse, these types of plants seem to express these pesticides at higher, more toxic levels than commercial crops. Vera Krischik, an entomologist at the University of Minnesota, says that imidacloprid expresses itself in soil-treated plants like garden flowers at a much higher dose than for seed-treated plants like corn.

Many pesticides approved for home and garden use also contain neonicotinoids, particularly imidacloprid.

Taking Action

Some countries are already taking action on neonicotinoids. The Dutch government has banned imidacloprid in open-air situations. Just this year, the European Commission recommended a moratorium across the EU. In April, 15 of 27 EU member states voted to enact a 2-year ban on the use of three neonicotinoids. The law prevents the use of these pesticides on flowering plants for two years until more evidence comes in.

In the U.S., the EPA stated it was taking a closer look at this class of pesticides, but so far their only action has been to release new labels with a “bee-advisory box” explaining how to minimize harm to the insects.

Here are some tips for how you can help—please let us know if you have more:

  • Go chemical free—choose only green pesticides to control pests in your lawn and garden. Choosing organic foods at your supermarket also supports bee-friendly agriculture.
  • Avoid store-bought flower pesticides—those you buy off the shelf, such as Bayer’s 2-1 Systemic Rose and Flower Care, may include neonicotinoids (list below).
  • Ask for change: Right now, you can’t tell when you buy a plant if it is contaminated with neonicotinoids. Friends of the Earth has asked top garden retailers to stop selling the pesticides and plants pre-treated with them. You can join the new U.S. campaign at the following website:
  • Show support: In early summer 2013, two Congressional Democrats co-sponsored new legislation called “Save America’s Pollinators Act of 2013” to take emergency action to save the remaining bees in the U.S. Show your support on the Friends of the Earth website.

For a list of common home and garden products containing neonicotinoids, see the Center for Food Safety’s handy chart.

Do you know more about what’s happening with our honeybees, and how we can help? Please let us know.

* * *

“Honey Bees and Colony Collapse Disorder,” USDA,

Ryan Gorman, “More Than 50,000 bees killed in Oregon, insecticide blamed in largest bee die-off in recorded history,” Daily Mail, June 23, 2013,

“Bee die-offs: New tests find bee-killing pesticides in ‘bee-friendly’ plants from garden centers nationwide,” Friends of the Earth, August 14, 2013,

Jennifer Hopwood, et al., “Are Neonicotinoids Killing Bees?” The Xerces Society for Invertebrate Conservation,

Rebekah Marcarelli, “Bee-Killing Pesticides Must be Labeled; Will EPA’s New Guidelines Make a Difference?” Headlines & Global News, August 21, 2013,

Tom Philpott, “Is Your Garden Pesticide Killing Bees?” Mother Jones, January 17, 2012,

Colleen M. Story

Colleen M. Story

Colleen M. Story, a northwest-based writer, editor, and ghostwriter, has been creating non-fiction materials for individuals, corporations, and commercial magazines for over 17 years. She specializes in the health and wellness field, where she writes and ghostwrites books, e-books, blogs, magazine articles, and more.

Colleen is the founder of Writing and Wellness. Her fantasy novel, “Rise of the Sidenah,” was released with Jupiter Gardens Press in September 2015. Her literary novel, “Loreena’s Gift,” is forthcoming in spring 2016 from Dzanc Books. She lives in Idaho.

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