Princep 80W, 90W, 4G, 4L and Caliber 90 DG were tested on 54 plant genera or species over a sixteen year period (1973- 1989). Data in this report were generated to expand registered uses of simazine on ornamental species. Simazine rates in trials included 2, 4, and 8 lb ai/A as the 1X, 2X, and 4X rates. Fifteen genera or species in the trials conducted have successfully been added to the Princep label, as well as, six weed species, based partially on IR-4 research. Studies showed satisfactory crop safety on additional genera/species not currently registered. Seven crops offer potential for label expansion (Acer rubrum, Acer saccharum, Buxus microphylla var. koreana, Leucothoe sp, Lilium longiflorum, Photinia sp, and Pyracantha sp.). Two crops demonstrated little to no injury at the 1X rate but the 2X or 4X rate did cause significant injury (Forsythia and Rhododendron). Enough damage was found on two ornamental crops to warrant not using this product: Arctostaphylos, and Euonymus radicans. Five weed species appeared to be susceptible to simazine treatments and merit further evaluation prior to label expansion including horseweed, London Rocket, oxalis, spotted spurge, and wild strawberry. IR-4 research previously supported adding 10 weeds to simazine labels.
