Back in April, I contacted Tom Whitehair (Anne & Tom Whitehair [mailto:[EMAIL PROTECTED] <mailto:%5bmailto:[EMAIL PROTECTED]> ) regarding the effectiveness of Physan as a viricide. He was very helpful and sent me a lot of printed material. Physan bills itself as a bactericide, fungicide, algaecide, and viricide. The general dose for most purposes was anywhere from 1 tsp to 1 Tbsp per gallon. I've used 1 tsp/gal on newly unflasked seedlings with great results. I use 2 tsp/gal as a fungicide is potted plants during our hot, humid summers. Three tsp (1Tbsp) was recommended for treating tools, greenhouse walkways and walls, mature infected plants, etc. I've had great luck with Physan stopping erwinia in its tracks. It also takes care of powdery mildew on my dwarf roses (watch the dose though). Generally speaking, I've seen little difference in plant tolerance to any of these strengths applied as a spray, drench or soak.
I asked Tom about their claim of efficacy on TMV and the data they supplied was 30 years old. I asked about this and they said no follow-up studies have been done. At this point they are concentrating on expanding their market particularly into more profitable areas. I guess orchid growers just don't use enough of their product to make it worthwhile to update old studies with modern techniques. I shared this information with AJ Hicks at the time. So AJ, if you have something more to add here, please do so before I overstep the boundaries of what I know and inferences I shouldn't make. Gary
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