This is the only thing I found about citronella when I googled it:
"Your site lists citronella as being toxic. Does that mean that citronella anti-barking collars are dangerous to dogs?
—Ted D.
The answer is no, Ted—in most cases. While citronella oil does have the potential to be toxic in large amounts, the amount many collars use in their spray is relatively small. Most contain about 10 percent citronella. This level might potentially be an issue for animals who have a history of respiratory problems, but otherwise we would not expect to see any problems."
That was on the ASPCA Animal Poison Control website....here's the link:
ASPCA: Ask the Animal Poison Control Center: Okay or No Way?: Miscellaneous
Also, this website lists Rosemary as being inadvisable to use on dogs....google "Rosemary Dogs toxic" and see what you find:
Chinaroad Lowchens of Australia - Ticks, fleas, bees, flies, snakes and other gremlins! And how to deal with them! (near the bottom: "Oil NOT to use")
However, that particular website also says Tea Tree Oil is ok to use, but it is a known toxin to dogs (and even more so to cats)....
Tea Tree Oil is toxic to Pets - WARNING
and
http://www.petcarenaturally.com/hand...a-tree-oil.pdf
(it says that "Tea tree oil can result in a fatal toxicity in cats when
ingested. Some holistic veterinarians prefer not to
use tea tree oil in small dogs and cats to guard
against any potential toxicity.")