Home gardeners beware of pesticides in potting soils & nursery plants

This past Tuesday at the monthly meeting of the Somerset Beekeepers, we hosted Gary Fish from the Maine Board of Pesticide Control to talk with us about “Pesticides and Pollinators”.  We are a small group, so I’m always grateful that any knowledgeable speaker should come to Skowhegan to share their knowledge with us, and I know that our beekeepers are eager to learn what these people have to offer us.

Gary Fish was well prepared, with a myriad of printed hand-outs for us, and a lengthy slide-show presenting his information on all aspects of pesticide use related to beekeeping and pollinator conservation.  He talked about the recent EU Commission to restrict the use of 3 neonicotinoid pesticides, and about bee-decline and bee-losses.  He talked about the results thus far from the managed pollinator coordinated agriculture study that is still on-going, and about the possibility of GM crops affecting honeybees.  By the way, according to Gary it’s not the actual GMOs causing honeybee losses, but the resulting loss of diverse habitat.  Personally I wasn’t sold on that one, knowing what I do about how GMOs affect animals (even humans) and how little objective scientific study has been done–sorry Gary!

But one thing that really stuck out from Gary Fish’s presentation was the fact that many nursery plants are grown and treated with pesticides, and even some potting soils may contain these harmful chemicals.

Actually I was already aware that nursery and greenhouse growers typically apply pesticides and fungicides to seedlings–it was about that time that I stopped buying my plants from other growers and started growing them in earnest myself.  Better to have leggy tomatoes than tomatoes drenched in chemicals!

What came as a shock, was when Gary told us that even some potting soils contain pesticides, and many homeowners are using the stuff without even realizing it!  He explained how important it is to read the labels on the potting soil, and guiltily I realized I had not done so.  Filled with anxiety at the horrifying thought that I might have unwittingly grown all of my precious vegetable, herb, and bee-foraging plants in contaminated soil, I hurried home after the meeting to check the label on my potting medium.

I’ve used the same soil-less potting mixture for years–Pro-Mix BX Mycorrhizae–I buy it by the bale at Campbell’s True Value across the river in Madison.  When Runamuk has grown older and larger I have every intention of formulating my own mixture, but for now this medium serves me well.  Imagine my relief when I found that the only ingredients were peat moss, perlite, vermiculite, dolomitic and calcitic limestone, a wetting agent (though it does not specify what this actually is) and mycorrhizae.

According to Gary Fish seeds are treated with pesticides and/or fungicides as they are planted–in some cases, such as with ornamentals, they are treated with enough chemiccals to last throughout the entire life of the plant!  So even if you’re committed to organic gardening methods at home, if you purchase your seedlings at a nursery or greenhouse, your plants may still be producing harmful pesticides.

Neonicotinoids, like imidacloprid, that are used in nurseries and greenhouses, and in some home gardening products like potting soils, are rated “Highly Toxic” to bees.  A lethal dose of 2 micrograms per bee will kill up to 50% of the colony’s population.  Systemic pesticides like these are applied to the seeds and are then are taken up through the roots to spread throughout the entire plant, and sequesters in the nectar and pollen of the flowers.

Mace Vaughan director of the Xerces Society’s Pollinator Program says:

Unfortunately for beneficial insects, ornamental plants may be treated with significantly higher doses of these chemicals than plants grown as food crops.  The result is that home gardeners may be growing poisonous plants without even knowing it.”

Then, as in the case of the pesticide ridden potting soils, there is the issue of handling and storage.  Ideally consumers should wear rubber gloves when using these products.  Also, to prevent soil and water contamination from pesticide run-off, un-used portions of these soils should be stored under a roof in an area protected from the elements.

Some examples of potting soils containing harmful chemical insecticides are Bayer’s Advanced Gardening 3-in-1 Multi-Purpose Potting Mix, Bayer Advanced Garden Tree & Shrub Planting Mix, and Bayer Advanced Garden Multi-Purpose Potting Mix with Moisture Control.  And some products contain herbicides like Shultz Premium Mulch with Weed Stop.  Insecticides and herbicides are both harmful pesticides.

Do not use potting soils containing pesticides to grow your edibles, wear protective rubber gloves when handling the soil, and be cautious of allowing children to touch it too.

It’s misleading for home-gardeners, because these pesticides look like potting soil, but they ARE a pesticide–but it doesn’t come in a spray bottle so it doesn’t look like a pesticide.  That’s why it is imperative to always read the label.

 References

Read the Fine Print: Expert Issues Warning about Pesticide-Laced Potting Soil

Ask a Gardener – from the North Carolina Cooperative Extension

Potting Soil & Mulch Can be Pesticides – The Buzz; the Bulletin of the Maine Board of Pesticide Control

Plant Buyer, Be Wary – The BeeLine from the Maine State Beekeeper’s Association