Residues on Ryegrass Following Preplant or Postemergence Applications of Four Insecticides for Mole Cricket Control1

Abstract

Ryegrass was treated with chlordane, diazinon, Dyfonate® ( O -ethyl S -phenyl ethylphosphonodithioate), and trichlorfon in bait and granular formulations. Pesticides were applied as a preplant treatment disked into the soil or as a single application to the grass 7 weeks after planting. Chlordane residues on ryegrass after a single foliar application of 0.5 and 3.0 lb per acre followed by 21 days of weathering were 2.1 and 3.2 ppm, respectively. Preplant application of 3.0 lb per acre of chlordane resulted in grass residues below 0.3 ppm throughout the sampling period. Following a 2.0-lb-per-acre foliar application of 14% diazinon granules, residues decreased from 15.3 to 0.3 ppm during the 21-day weathering period. Diazinon residues of less than 0.1 ppm were detected on grass samples taken 50 days after a 2.0-lb-per-acre preplant application to the soil. Dyfonate residues decreased from 16.8 to 0.5 ppm. during the 21-day period after a 2.0-lb-per-acre foliar treatment. Under the same conditions, residues of Dyfonate oxygen analogue were found to be less than 0.2 ppm. after a 2.0-lb-per-acre preplant application to the soil, residues of Dyfonate or its oxygen analogue were insignificant. Trichlorfon residues decreased from 37.5 to 0.1 pm during the 21-day weathering period after a 1.0-lb-per-acre foliar application.