Yes, Australian Nut is toxic to dogs!
Dogs accidentally consuming the Australian Nut 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).
More Info About The Australian Nut Plant
Scientific Name: Macadamia integrifolia
Family: Proteaceae.
Also known as: Macadamia Nut, Queensland Nut.
The answer is based on information found on The American Society for the Prevention of Cruelty to Animals (ASPCA) website.