STS and CS blocks the plant from producing female hormones, but not by changing the genetics of the plants. If not done several times over the course of 2 weeks the effects wear off and the plant begins to produce the hormones again. It's also applied on the fan leaves, which aren't consumed anyways since you are just looking for pollen to use to produce seed on a totally different plant. To say that seed producers are not using it because it's poisonous is totally false...show me the proof. STS and CS is TOTALLY safe to use in the production of seeds and Ga3 is commonly used to form roots on cuttings.