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Five spray mixes of mexacarbate (4-dimethylamino-3,5-xylyl N-methylcarbamate) were prepared using different inert ingredients. Among the mixes, ZE-DIL was oil-based, ZE-EML-1 14 and ZE-EML-3409 were emulsions, ZE-WP-W was a wettable powder in water, and ZE-FL-W was a flowable in water. The mixes were sprayed over potted balsam fir [Abies balsamea (L.) Mill.] seedlings in a laboratory chamber and foliar residues were analyzed by gas chromatography. The results showed that the ratios of the initial dislodgeable to penetrated residues were low for ZE-DIL, ZE-EML-114 and ZE-EML-3409, but were high for ZE-WP-W and ZE-FL-W. The latter two spray mixes contained mexacarbate in the particulate form, and contributed to greater surface residues than those of the former three spray mixes which contained mexacarbate in the solution or emulsion form. Foliar residues declined rapidly during 0 to 3 d post-spray, with half-lives (DT 50 ) ranging from 0.84 to 1.73 d. The rate of decline was slow from 3 to 20 d post-spray and the DT 50 values ranged from 2.49 to 4.65 d. Mexacarbate volatilized and codistilled appreciably within 24 h. Volatilization occurred more from dislodgeable residues than from penetrated ones, whereas codistillation occurred from both dislodgeable and penetrated residues. The penetrated residues of ZE-WP-W and ZE-FL-W volatilized less than those of ZE-DIL, ZE-EML-114 and ZE-EML-3409. This behaviour was due to the presence of mexacarbate in the particulate form in the former two spray mixes, as opposed to its presence as a solution or as an emulsion in the latter three spray mixes.

Mobility and metabolic fate of 14 C-mexacarbate (4-dimethlyamino-3,5-xylyl N-methylcarbamate) were studied using columns containing sandy and clay loam forest soils. Flooding and subsequent analysis of the soil segments showed the presence of free and bound (nonextractable) residues. The bulk of the 14 C-labelled material was adsorbed onto the litter layers. However, when the columns were saturated with 454 μg of the material, a small part of the radioactivity moved beyond the column length into the leachate. Analysis of the litter segments and the leachate showed carbamate moieties, phenols and other metabolites. Incubation of the soil columns under aerobic (dry) and anaerobic (wet) conditions for 30 d showed the retention of radioactivity in litter layers. The quantities of mexacarbate and its degradation products found were influenced, to some extent, by the soil type and incubation conditions. Except for phenolic and polar metabolites, no intact carbamate moieties were found in the litter after the 30-d incubation period. Mexacarbate seemed to breakdown rapidly in forest soil columns into various degradation products. A metabolic pathway for its degradation in soil is proposed.

The distribution and persistence of aerially applied mexacarbate were studied in a New Brunswick aquatic forest environment after spraying twice at a dosage of 70 g A.l./ha using a fixed‐wing aircraft. Average droplet density (drops/cm2) and ground deposition (g A.1./ha) between the two applications differed considerably. The values for the first and second applications were 1.7 and 0.73, and 5.2 and 2.0, respectively; but the average NMD (20 μm) and VMD (36 μm) for both applications were nearly the same. The maximum 1‐h postspray concentrations of mexacarbate in the stream and pond waters were 0.73 and 18.74 ppb, respectively. Concentrations fell rapidly to below detection limits within 12 h in stream and within 3 d in pond water. Cattails (Typha latifolia), manna grass (Glyceria borealis) and bog moss (Sphagnum sp.) collected from the pond contained peak 1‐h postspray concentrations of 720, 482 and 81 ppb, respectively. The concentration levels decreased rapidly and the average half‐lives of th...

Mexacarbate (4‐dimethylamino‐3,5‐xylyl N‐methylcarbamate) insecticide has potential for use in spruce budworm (Choristoneura fumiferana Clem.) control operations in Canada. Its persistence and fate in balsam fir (Abies balsamea (L.) Mill.), litter and soil samples were studied by spraying aerially oil‐based and water‐based formulations, each at 70 g A.I./ha over a coniferous forest near Bathurst, New Brunswick. The oil‐based formulation gave the maximum concentration of the chemical in the substrates studied. In fir needles, the highest concentrations observed were 0.51 ppm and 0.19 ppm (fresh weight) for the oil‐based and emulsion formulations respectively, 1 h after application. The residue levels decreased very rapidly with a half‐life of approximately 5 h. Three and eight days after the spray application of the emulsion and oil formulations respectively, the concentrations of mexacarbate in foliage decreased to trace levels ( 0.008 ppm). Only very low levels of residue were detected in litter...

The degradation and metabolism of mexacarbate were studied in two types (sandy loam and clay loam) of sterile and nonsterile forest litters after incubation for 45 days under aerobic and submerged conditions. Degradation of the chemical in non‐autoclaved litters was rapid initially and reached a maximum after 30 d. The rate of formation of 14CO2 and the amount, the extractable metabolites produced and the nonextractable 14C adsorbed onto the litters varied depending on the litter type and experimental conditions. Rate constants and half‐lives (t1/2) of evolution of 14CO2 were very similar for the aerobic and submerged conditions. However, the t1/2 values for the clay loam litter were slightly higher than those for the sandy loam litter. Litter microbes played a major role in the degradation of mexacarbate and formation of 14CO2. Metabolites detected included demethylated carbamates, various xylenols, polar and other unknown products. The principal degradative pathway for the chemical appears to b...

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, ami‐nocarb 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 Al2O3 column to remove plant pigments. EAR concentrations were quantified using Turner Fluorometer. 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 ...

Volatilization of three forestry insecticides, aminocarb, fenitrothion and mexacarbate, from balsam fir seedlings was investigated after spray application of these chemicals as aqueous emulsions in a laboratory chamber at a dosage rate of 210 g (active ingredient)/ha. Highest airborne residues were found in the spray chamber at 0.25 h after mexacarbate application (21.7 μg/L) and lowest after aminocarb (6.3 μg/L). The treated seedlings were transferred to air‐tight chambers for investigation of volatilization over a 12 h post‐spray period. Mexacarbate was the most volatile, while aminocarb was the least. From the initial amounts of deposits on the seedlings, about 30% of mexacarbate, 15% of fenitrothion and 9% of aminocarb were lost within 12 h by volatilization. Residue levels that remained in the seedlings at 12 h post‐spray were ca. 70% of the initial values for aminocarb and fenitrothion, but were only ca. 9% for mexacarbate. Calculations on the mass‐balance indicated that 60% of the deposite...