Influence of Application Volume, Post-Application Irrigation and Mowing Height On Prodiamine Foliar Residues Following Application to a Tall Fescue Lawn.

Persistence of dislodgeable foliar residues (DFR) following pesticide application is an important concern because of implications for human exposure. This study determined the influence of application carrier volume, post-application irrigation and mowing height on the persistence of  prodiamine (5-dipropylamino-α,α,α-trifluoro-4,6-dinitro-o-toluidine or 2,6-dinitro-N¹,N¹-dipropyl-4-trifluoromethyl-m-phenylenediamine ) residues following application at 793 g a.i. ha^-1  to a mature stand of ‘Confederate’ Tall Fescue (Festuca arundinacea Schreb).  Prodiamine was applied using a single nozzle Chemlawn Gun at a carrier volume of either 810 or 1,236 L ha^-1.  Immediately following application plots were allowed to dry or received 0.6 cm of post-application irrigation to water in the treatments.  DFR were monitored for 11 days following application.  Increasing application  carrier  volume  from 810 to 1,236 L ha^-1 reduced DFR by an average of 3.8% over the entire study with significantly lower residue levels 3 hours after treatment (HAT), and 5, 7, and 11 days after treatment (DAT). Increased application volume resulted in an average of 46% less prodiamine soil  residues with significantly  lower residue levels 1, 3, and 11 DAT. Clippings  removed from plots receiving an application volume of 810 L ha^-1 compared to 1,236 L ha^-1 exhibited a 13% reduction in the amount of applied prodiamine lost from the treated surface. Post-application  irrigation reduced DFR by  an average of 10%  over the duration of the study with significantly lower residue levels for all sampling periods except 3 DAT. Clippings removed from plots that received post-application irrigation exhibited a 12% reduction in the amount of applied prodiamine lost from the treated plots.  Maintenance mowing heights of 12.7 cm vs. 7.6 cm did not significantly affect DFR throughout the entire study. Increased mowing height resulted in an average of 28% higher prodiamine levels in soil for all sampling periods except 3 DAT; however, they were not statistically different during any sampling period. Prodiamine residue levels resulted in a maximum estimated hazard quotient of 1.18 x 10^-3 for study, indicating no potential human toxicological effects from maximum field residue levels.