How long do old pesticides stay in the ground? - Ask Extension
I moved to Oregon last summer and am preparing to plant my first vegetable garden here, but it's obvious that the original owners of the house- who ha...
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How long do old pesticides stay in the ground? #447296
Asked April 11, 2018, 3:35 PM EDT
I moved to Oregon last summer and am preparing to plant my first vegetable garden here, but it's obvious that the original owners of the house- who haven't lived here in at least 10 years- were obsessed with the lawn. There is a closet in the garage containing every pesticide, herbicide, mildewcide, etc, most with labels that look like they're from the 1970's to early 80's. The subsequent tenants have not touched the yard other than mowing occasionally. The soil drains well but is pretty heavy on clay and feels compact. I needed multiple sharp tools to cut through sod and dig for planting tulip bulbs.
I can't find a soil test that includes pesticides which I can readily afford, and I'm wondering if it's even needed- is there anything potentially harmful to my family that wouldn't have leached out long ago?
I see three options within my budget at this point, and not sure which is smartest/safest:
1. Don't worry about the long-dispersed toxins, spread 4" of compost on a large bed area and till;
2. Panic about the toxins, build a couple of small raised beds, not enough to feed my family, and hope I have more money for raised beds or remediation next year; or
3. Build Hugel-style mounds at least a foot tall with woodchips and branches, assuming any interaction with the current soil layer will be minimal.
Suggestions?
Multnomah County Oregon
Expert Response
Hi there- Boy! That's a great question!
It's good news, to hear that the previous occupant was not such a heavy pesticide user. Most of the very persistent pesticides were banned in the 70's and 80's. They were replaced with insecticides that break down in a matter of months, rather than years. Herbicides have always been less persistent, breaking down in a matter of weeks. You mentioned a mildewcide, and I'm not sure about that one. There are several types of mildewcides. If you have the label, and you can handle it safely, please collect that label and call the National Pesticide Information Center (NPIC) between 8:00 am and 12:00 noon - at <personal data hidden>. They can tell you about the persistence of the mildewcides.
Your ideas for growing vegetables are great. Making raised beds or mounds with fresh soil would help. Creating a barrier between old soil and new soil, such as landscaping fabric, would also help. However, there may be no need for concern after so much time has passed. The kind of pesticides that might bind to soil and persist for years, those are not the kind that can be easily dislodged (from the clay) and absorbed by roots. They're much more likely to stay bound up with the clay particles.
I hope that information is helpful. Feel free to write with any follow-up questions!
Thank you for your patience.
Kaci
It's good news, to hear that the previous occupant was not such a heavy pesticide user. Most of the very persistent pesticides were banned in the 70's and 80's. They were replaced with insecticides that break down in a matter of months, rather than years. Herbicides have always been less persistent, breaking down in a matter of weeks. You mentioned a mildewcide, and I'm not sure about that one. There are several types of mildewcides. If you have the label, and you can handle it safely, please collect that label and call the National Pesticide Information Center (NPIC) between 8:00 am and 12:00 noon - at <personal data hidden>. They can tell you about the persistence of the mildewcides.
Your ideas for growing vegetables are great. Making raised beds or mounds with fresh soil would help. Creating a barrier between old soil and new soil, such as landscaping fabric, would also help. However, there may be no need for concern after so much time has passed. The kind of pesticides that might bind to soil and persist for years, those are not the kind that can be easily dislodged (from the clay) and absorbed by roots. They're much more likely to stay bound up with the clay particles.
I hope that information is helpful. Feel free to write with any follow-up questions!
Thank you for your patience.
Kaci
Wow, thank you so much for your prompt, thorough, and useful answer!
You are most welcome.
Enjoy your 'firsts' this year!
Enjoy your 'firsts' this year!
