A simple method for quantifying Erio acid red dye in spray deposits of some pesticide formulations on conifer foliage

Abstract

A simple method was developed to quantify a fluorescent dye tracer [Erio Acid Red (EAR)] in spray deposits of forestry insecticides on balsam fir foliage. Three types of instruments, Beckman DU-7 Spectrophotometer, Beckman Model 772 Ratio Fluorometer, Turner Model 111 Fluorometer, were investigated for sensitivity and precision during quantification of EAR in aqueous tank-mix formulations of fenitrothion, aminocarb and mexacarbate. Turner Fluorometer was found to be the most suitable out of the instruments tested, and the minimum detection limit was 0.5 ng/mL. Foliage samples were spiked with variable concentrations of EAR, extracted at different intervals of time after treatment, and cleaned using an Al 2 O 3 column to remove plant pigments. EAR concentrations were quantified using Turner Fluo-675 676 SUKDARAM, SUNDARAM, AND LEUNGrometer. Recovery was the greatest when extracted 12 to 15 min after spiking, but decreased rapidly as the time lapse between treatment and extraction increased. The minimum quantification limit (MQL) was 10 ng/g at 90% recovery, but was lower at a recovery value < 90%.The three insecticide formulations were sprayed onto fir seedlings in a laboratory spray chamber using dosage rates that would provide a deposit, on glass plate, of 16% of the field dosage rates. Foliar deposits were extracted, cleaned and quantified for the active ingredients (AI) by gas-liquidchroma tography, and for EAR by fluorometry. Foliar deposits of AI were similar to those obtained in previous field studies. Under these conditions, foliar deposits of EAR were ca. 70 ng/g which was well above the MQL of the method developed.The data, thus, demonstrated the suitability of the present method to quantify insecticide deposits on canopy foliage in aerial spray trials over conifer forests.

Deposition, distribution, persistence and fate of bacillus thuringiensis variety kurstaki (BTK) in pecan orchards following aerial and ground appucations to control pecan nut casebearer larvae

“…However, the poor correlation observed in this study between dye content and ô-endotoxin level is in contrast with the good correlation found between the dye content and residues of conventional insecticides in conifer foliage (Sundaram et al, 1989b). The reason for this difference lies in the homogenous distribution of insecticide materials in the 1989 spray-mixes.…”