Published online by Cambridge University Press: 12 June 2017
About 25 ppm of 4-amino-3,5,6-trichloropicolinic acid (picloram) usually were detected on grass, primarily buffalograss (Buchloe dactyloides (Nutt.) Engelm.) and blue grama (Bouteloua gracilis Willd. ex HBK Lag ex Griffiths), immediately after application of 0.28 kg/ha picloram + 0.28 kg/ha (2,4,5-trichlorophenoxy)acetic acid (2,4,5-T) in northwest Texas. Less than 1 ppm of picloram usually was detected in grass tissue 30 to 60 days after treatment. At one location, detectable picloram increased in grass tissue from 32 to 60 days after application. Increases of picloram in aerial grass tissue were attributed to root uptake during a flush of vegetative growth. Picloram dissipation from grasses was not affected by irrigation to runoff at 10, 20, or 30 days after application. Detectable picloram was reduced by 93% in herbaceous, broadleaf species by 30 days after application. Treated sand shinnery oak (Quercus havardii Rydb.) leaves at the soil surface caused a slight increase of picloram in surface litter.