The Castor Bean seeds' toxic compound Ricin, not being water soluble, is not in Castor Oil; unless due to production cross contamination. From USA National Institute of Health (1992) (= NIH pub 92-3131) regarding castor oil: * human toxicity = 1-2 pints orally of undiluted castor oil * human hyper-sensitivity possible = angiodema, asthma, rhinitis & scalatiniform rash in oil production workers * 10% castor oil dietary component fed experimental rats conclusion = no toxicity to any specific organ, organ systems or tissue; ie: no histo-pathological lesions & no hepato-toxicity from Castor oil * Ricinoleic acid is +/- 87% of Castor bean oil = a fatty acid liberated in small intestine by lipase enzyme & it is poorly metabolized, so residues linger in G-I tract * effects of Ricinoleic acid = inhibition of water & electrolyte absorption, stimulates water secretion into large intestine lumen & depresses small intestine contractions

My husband, and I live on 20 acres 11 miles outside of Bend OR. Voles have destroyed our lawn my husband has flooded the holes w/water, he's loosened them, he even started shooting them with his 410 shot gun. I started a butterfly/hummingbird garden last year, and everyday I'd go out to work, and they had feasted the night before. I bought just regular Castor Oil (consumable by humans) I put it into a sprayer, diluted it just enough so it wouldn't clog, and went out and sprayed the plants in my garden. It's only been a couple of days, and so far I haven't seen any. I even poured pure Castor Oil around the base of the plants. My husband is going to spray out lawn, and I suggested that we pour undiluted Castor Oil into the holes. We don't have a lot of lawn around our house, just enough to enjoy. I'll keep you posted. I'm going to be starting my veggie garden soon, and I'm goings to use the same process. I hope this helped !

The guys at Michigan State University that did the research on Castor Oil to repel moles said you need a mixture of 1 pint of Castor Oil in 1 quart sprayer filled with water and sprayed over 1,000 square feet. Anything short of that will not work. The Castor Oil coats and flavors the various insect larva the moles eat making them distasteful, there is no scent involved. Go to your local drug store and purchase the bottles of Castor Oil they sell since all of the so called Castor Oil sprays I have seen at the yard and garden stores have too little Castor Oil in them and are meant to be sprayed over too large an area (10,000 square feet) to be effective.

Ken, last year I only had one that I believe was damaged by voles. Before that, I didn't have so many hostas. I've lost several through the years but I don't know if those losses were due to voles or not. I believe voles may have gotten into a couple of oak leaf hydrangeas in recent years. By probing with my fingers around the damaged hostas, I found clear evidence of tunnels around two of them. The other two seem to be in solid ground -- their damage could be from a couple of unusual freezes we've had.