NO! Do not use mothballs. They will poison dogs, cats and even children who might get their hands on them.
Thank you for the information you shared on some toads being poisonous, and the problem this is with dogs. I would like to comment on or question the 'remedy' submitted about using moth balls placed around the property to repell the toads. I believe the moth balls themselves may be a problem because of toxic fumes, or possible ingestion by animals.
Bufo Toad Remedies: I tried the mothballs and they did NOT work at all. They smelled bad and I had to collect them all back up. It was a "bad' experience.