I have previously been nearly or all organic. Last year for fun I grew organic peas in the garden and treated seeds in a container- just to try it without adding possible toxins to my garden if it didn't work. The container peas were miserable, but the organic peas in the garden took off without any added chemicals or pre-treatments (we're talking right out of the bag here). Then, they shriveled up and died shortly after a good harvest (so glad it waited until then). This year I purchased snow peas from Gurneys and after I bought them, I realized they were treated with Captan. I've done a little reading which might suggest that it inhibits calcium from entering the root system, but I can't find much on how much of the fungicide becomes ingrained in the edible part of the plant, how quickly it leaves the soil, how beneficial it really is, and if it affects soil microbes negatively. I'm trying to decide if I should be frugal and use the seeds I've already bought and risk going chemical, or buy more organic seed instead and risk the possibility of disease. I don't have the time it takes to mess with something that's not tried and true. Please share advise and experience!
I've planted Captan seeds before. Personally I don't think it's that big a deal. It's put on the seed to keep it from rotting when planted in marginal temperature soil. I don't believe it's something you need if your soil is warm enough, on the other hand I don't think it hurts all that much if it is there unless you are marketing organic produce. If I plant two sets of seed one that is and one that isn't treated with Captan I don't see a difference in the plants either in density or vigor.
The Captan treatment of seeds is purely to prevent any seed borne fungal diseases, of which there are several. Captan is a "cheaper" way of doing that. There is a thermal treatment, somewhat similar to pasteurizing milk, involving the precise heating of the seeds to an exact elevated temperature for a specific amount of time that can also kill any seed-borne fungus, but that equipment costs much more than just throwing in a little Captan. Be sure to wash your hands well after handling any Captan treated seeds. And while you are planting Captan treated seeds, don't stick your fingers in your mouth, handle chewing gum or a cigarette, eat a cookie, etc.
If you are on a tight budget and the cost of a package of seeds is an issue, I would go ahead and plant them. No, it is not organic - but yes, it is "tried and true"; treated seeds have been around for a long time. When I was a kid, you couldn't get untreated seed for certain plants unless you saved your own seed. But for next year, you pobably don't need treated seed.
Agree with Zen_Man - wash hands with soap after handling. And if you decide to wash or presoak your seeds, do it in something disposable - not your favorite coffee cup or the dog's water dish, etc.