What Can Weed & Bush Killer Do to Dogs?

Updated November 21, 2016

Dogs are poisoned by most of the same substances as people, although the effects in dogs can be faster-acting. Non-selective weed killers such as paraquat are commonly used and favoured because they kill the root of the plant and will kill any plant that it comes in contact with. Herbicides containing organophosphates are also a source of poisoning in dogs, with citrus oil and 2,4,-dichlorophenoxyacetic acid -- a weedkiller -- that produces deleterious effects in dogs.


Once ingested, paraquat undergoes chemical reactions that produce tissue damage, often concentrating in the lungs or kidneys with significant damage to mucous membranes after ingestion. Early symptoms include vomiting. Anorexia, lethargy and inappetence may also be present. Death can occur one to four days after systemic poisoning from renal failure and pulmonary edema.Treatment consisting of stomach pumping and application of an adsorbent, such as activated charcoal, to neutralise the ingested paraquat must be done within hours of ingestion to be effective.


Organophosphates affect the dog's nervous system and are absorbed through the skin, respiratory tract and gastrointestinal tract. According to Pet, the toxic dose varies through route of exposure. Symptoms include drooling, difficulty breathing, tremors, vomiting and poor balance and coordination. If the dog's skin was exposed, bathe the dog immediately and rinse thoroughly. If ingested, induce vomiting only if the dog is conscious and seek veterinary care. The veterinarian may pump the dog's stomach and administer intravenous fluids.

Citrus Oil

Citrus oil is often touted as a natural herbicide, but it can be toxic to dogs. The toxic dose for d-Limonene, a component of citrus oil extract, is reportedly 308g per lb. of body weight. Symptoms include low blood pressure, drooling, hypothermia and dermatitis. In cases of skin contact, bathe the dog with warm dish water until the citrus smell is gone; dry thoroughly and do no allow the dog to become chilled. If ingested, do not induce vomiting due to risk of aspiration. Take the dog to a veterinarian, who may need to administer fluids.

2, 4 D

According to a study performed by the National Cancer Institute, the weedkiller 2,4,-dichlorophenoxyacetic acid increases the risk of lymphoma in dogs exposed to yards treated with it more than four times per year. Limit dogs' exposure to 2, 4-D-treated lawns for several days after its application until plants have absorbed the chemical and the sun has broken it down, the Los Angeles Department of Animal Care and Control website advises.

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About the Author

Based in Minneapolis, MN, Tammy Domeier began her writing career in 1998, writing user manuals for the commercial printing and graphics industry. She holds a Bachelor of Science degree in biology from Minnesota State University at Mankato and a paralegal certificate from Minnesota Paralegal Institute.