Yes, Ambrosia Mexicana is toxic to dogs!
Dogs accidentally consuming the Ambrosia Mexicana plants can show the following clinical symptoms: Vomiting, Prolonged Depression, Incoordination, Hypersalivaton, Sleepiness Or Excitation, Dilated Pupils, Low Body Temperature, Low Blood Pressure, Coma, Seizure And Death (In Rare Cases).
Ambrosia Mexicana consumption is also toxic to Cats and Horses.
Toxic Principles Of Ambrosia Mexicana: Sesquiterpene lactones.
More Info About The Ambrosia Mexicana Plant
Scientific Name: Chenopodium botrys
Family: Chenopodiaceae.
Also known as: Jerusalem Oak, Feather Geranium.
The answer is based on information found on The American Society for the Prevention of Cruelty to Animals (ASPCA) website.