Page 8 - Sonoma County Gardeners Resource Guide 2017.indd
P. 8

Gardener Alert!
Beware of Clopyralid & Aminopyralid
By Michala Jeberg
“It all starts with the soil.” As many gardeners know, improving soil
quality with organic matter is essential for growing healthy plants. Many gardeners rely on manure and compost to improve soil structure and to add slow-release nutrients. Unfortunately, these natural materials can become contaminated with herbicides. Even the slightest trace of troublesome chemicals such as Clopyralid and Aminopyralid can quickly kill hearty plants such as peas, beans, peppers, lettuce, spinach, potatoes, and tomatoes when found in soil or compost.
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Clopyralid and
Aminopyralid are widely
used herbicides that kill
many species of broadleaf
weeds growing in grain
fields, hay fields, and along
roadways. These man-
made chemicals are easily
absorbed by plants and
remain chemically intact
in live and dead plants. So,
if an animal eats hay or
grain from a producer who
has used these herbicides
to control weeds, the
chemicals enter the animal’s
digestive tract and do not
breakdown. These toxic
substances pass through the
animal into manure, urine,
and bedding, contaminating
any organic material with
which they come in contact,
e.g. soil and compost. A
concentration as low as one
to three parts per billion
will negatively affect the
growth of plants in the
nightshade category. Dow*,
the manufacturer of these
herbicides, claims that only
a few plants are affected.
These include some of our local garden favorites:
• Nightshade family - including tomatoes, potatoes, peppers and eggplant.
• Legume family - including lupines, peas, beans and clover.
Illustration from Dow AgroSciences’ label instructions for Aminopyralid
8 - www.sonomacountynurseries.com - 3/17
PHOTOS of herbiced impacted plants from Oregon State University and University of Maryland Extension
• Compositae family - including daisy, aster, sunflower and lettuces.
• Umbelliferae family - including carrots.
Symptoms of herbicide poisoning include reduced seed germination, distorted/twisted leaves and stems, stunted growth, low yields, and death.
Distortion of tomato leaves caused by Clopyralid
Zucchini leaves are strappy and cupped
How do Clopyralid and Aminopyralid end
up in our gardens?
Three main routes potentially bring these herbicides into gardens:
• Contamination resulting from herbicide drift. • Contaminated manure and bedding from
livestock fed crops treated with these herbicides. • Contaminated composts made from
contaminated hay, bedding, or manure.
BEWARE cont’d on page 9


































































































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