EFFECTS OF DIRECT CONTACT OF PINE SEEDS OR YOUNG SEEDLINGS WITH COMMERCIAL FORMULATIONS, ACTIVE INGREDIENTS, OR INERT INGREDIENTS OF TRIAZINE HERBICIDES

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Abstract
The effects of continuous direct contact of Pinus resinosa seeds and recently germinated seedlings with commercial formulations, active ingredients, or inert ingredients of atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine), simazine (2-chloro-4,6-bis(ethylamino)-s-triazine), and propazine (2-chloro-4,6-bis(isopropylamino)-s-triazine) were studied over a 27-day period. The concentration of active ingredients when used alone or in the commercial herbicide formulations was 1,000 ppm. The concentration of inert ingredients when used alone was equivalent to that in the commercial herbicide formulation. Seed germination was not affected by any of the herbicides but all were highly toxic to recently germinated seedlings. Phytotoxicity was variously demonstrated by reduction in dry-weight increment, suppression of root and shoot elongation, and killing of many seedlings. The active ingredients of each herbicide were responsible for most of the toxicity, but inert ingredients also caused some toxicity. Simazine and atrazine were much more toxic than propazine. Difficulties of assessing herbicide toxicity are discussed.