Kanth M. S. Sundaram

Environmental persistence and impact of diflubenzuron in a forest aquatic environment following aerial application

Dimilin® WP-25 (diflubenzuron) was applied at a rate of 70 g active ingredient (AI) in 10, 5, and 2.5 L/ha to three spray blocks in a mixed boreal forest near Kaladar, Ontario, Canada. Water, sediment, and aquatic plants were collected from two ponds and a stream at intervals up to 30 days post-treatment for analysis of diflubenzuron (DFB) residues. The duration of detectable residues was different for each substrate, but in all cases was less than two weeks. Zooplankton and benthic invertebrate populations were monitored for up to 110 days post-spray in two ponds in the high volume rate block and in control ponds. Significant mortality occurred in two groups of caged macroinvertebrates (amphipoda and immature corixidae) 1 to 6 days after the ponds were treated with Dimilin. Three taxa of littoral insects (Caenis, Celithemis andCoenagrion) were significantly reduced in abundance in the treated ponds 21 to 34 d post-treatment, but recovered to pre-treatment levels by the end of the season. Of the six remaining groups studied, only one (immature corixidae), may have been slightly affected by treatment. Zooplankton (cladocera and copepoda) populations were reduced 3 days after treatment and remained suppressed for 2–3 months.

An improved method to study the impact of pesticide sprays on small song birds

Abstract A survey for possible lead poisoning among workers of silver jewellery industry was undertaken. A large section of population has been engaged in different workshop. The environmental concentration of lead in workshop engaged in recovery of silver from dust, smelting‐alloying and assembling‐soldering have been found to be higher than the permissible limit. Out of 105 workers involved in various processes, 23 subjects were identified as suffering from mild to severe lead poisoning on the basis of laboratory and clinical data.

Mobility of diflubenzuron in two types of forest soils

Abstract Diflubenzuron (DFB) [l‐(4‐chlorophenyl)‐3‐(2,6‐diflurobenzoyl) urea] and its two formulatons, Dimilin® WP‐25 and Dimilin® SC‐48, were applLed separately at 17.23, 51.69 and 155.07 μg of active ingredient (A.I.) (corresponding to 70, 210 and 630 g A.I./ha) to the top layers of columns (30 x 5.6 cm i.d.) packed with either sandy or clay loam forest soils. Water (1.251 L) equivalent to 50.8 cm of precipitation was allowed to leach through each column. After leaching, the columns were divided into 5 unequal segments aud the DFB residues in soils were extracted and analyzed by high performance liquid chromatography (HPLC). Mobility of DFB was low and did not increase with dosage. At a deposit rate equivalent to 70 g A.I./ha, nearly all the residues were found within 2.5 cm of the top of the column. Mobility of DFB did not increase with dosage. Even at 630 g A.I./ha, only about 9% of the technical DFB, 7% of Dimilin SC‐48 and 4% of Dimilin WP‐25 moved below the 2.5 cm level in sandy loam. Mobility of D...

An evaluation of physical properties, droplet spectra, ground deposits and soil residues of aerially applied aminocarb and fenitrothion emulsions in conifer forests in new Brunswick

Abstract A comparative evaluation of physical properties, spray droplet spectra, ground deposits and soil residues was made for two aminocarb and two fenitrothion emulsions, following aerial application in New Brunswick, at dosage rates of 70 g active ingredient (AI) in 1.5 L/ha and 210 g AI in 1.5 L/ha, respectively. The aminocarb emulsions were less viscous and more volatile than those of fenitrothion. However, variations in droplet size spectra, number and volume median diameters were minimal among the four formulations, although significantly more droplets/cm2 and higher deposits in g AI/ha were obtained for the most viscous fenitrothion mixture. All emulsions showed similar surface tension values and therefore, the contribution of surface tension to droplet size spectra could not be demonstrated. All emulsions produced very low soil residues, but those of aminocarb were lower than those of fenitrothion. However, when differences in the dosage rates were taken into account, the residues were somewhat ...

Airborne permethrin and off-target deposits from an aerial ultra-low volume silvicultural spray

A 16 ha forested site with canopy height averaging 7 m was aerially sprayed with an aqueous permethrin emulsion, using active ingredient and volume application rates of 70 g ha−1 and 41ha−1 respectively. A fixed-wing aircraft equipped with Micronair AU 3000 atomizers dispersed a spray with a volume median diameter of 65 μm in a stable atmospheric boundary layer with a wind speed of 2.3 m s−1 and air temperature of 19°C at the spray height of 18 m above ground level. Measurements were made of airborne permethrin and off-target spray deposits on spruce foliage and fine-toothed combs at 2 m above ground level, and glass plates and Kromekote cards placed horizontally on the ground at various distances up to 250 m from the treatment area. Airborne permethrin was reduced by 60% between 0 and 250 m; over this distance the drop numbers per spruce needle decreased from 17 to 2.6 and drop densities on Kromekote ground cards and combs from 22 to 5.6 and from 87 to 18 drops cm−2. Volume median diameters on the Kromekote cards and combs were 49 and 38 μm, and showed no significant change between 0 and 250 m. Permethrin deposits on glass plates and aluminium combs decreased from 23 to 6 ng cm−2 and from 52 to 10 ng cm−2 between 0 and 250 m. Deposits on glass plates were compared with values calculated using a published swath superposition model and found to be in good agreement.

Field deposit patterns of a diflubenzuron spray mix, after application to an apple orchard using an air‐blast sprayer; and a laboratory evaluation of physical properties and atomization characteristics

Abstract Diflubenzuron (DFB) was applied to an apple orchard in Sodus, Wayne County, N.Y., USA, at the rate of 280 g active ingredient (AI) (or 1120 g of Dimilin® WP‐25) in 1430 L/ha, using an air‐blast sprayer’. Deposits were collected at ground level on target site and along downwind direction in the off‐target region, for assessment of droplet spectra and DFB content, before and after treatment. Physical properties, viz., viscosity at variable shear rates, surface tension, volatility and liquid‐atomization characteristics were also investigated for the spray mix under laboratory conditions. About 39% of the applied amount was deposited at ground level of the treated region. Deposits on the off‐target areas decreased extremely rapidly with downwind distance; recovery was about 3% at 15.24 m but reached a level below the detection limit beyond 60 m from the treated area. Droplet frequency (no./cm2) values showed a corresponding decrease. The DFB content of the spray mix, prior to and after treatment show...

Mexacarbate residues in selected components of a conifer forest following aerial applications of oil‐based and aqueous spray formulations

Abstract 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...

Simultaneous determination of fenitrothion and aminocarb in blueberry foliage and fruits: Application to the analysis of residues in field samples

Abstract Samples of blueberry foliage and fruits were collected from spray blocks in Ontario after aerial application of fenitrothion and aminocarb at dosage rates of 210 g active ingredient (AI)/ha and 70 g AI/ha respectively. Residues were extracted from the samples by homogenizing with ethyl acetate, cleaned up by microcolumn chromatography using alumina as adsorbent, and analyzed by GLC‐AFID with a glass column packed with 1.5% OV‐17 and 1.95% OV‐210 on 80–100 mesh Chromosorb W‐HP. Average recoveries for fenitrothion and aminocarb from foliage at three fortification levels (1.0, 0.10 and 0.01 ppm) were respectively 99 and 96%. The corresponding values for the fruits were 99 and 95%. Foliage samples collected 1 h post‐spray contained on average 1.13 ppm of fe‐nitrothion and 1.14 ppm of aminocarb. However, residue levels reached below the detection limit (<0.01 ppm) in foliage collected 15 d after treatment. In addition, the fruit samples collected after 15 d post‐spray contained extremely low levels (0...

Fenitrothion deposits on different components of a forest ecosystem during an aerial spray trial

Initial deposits of aerially applied fenitrothion insecticide over a boreal forest area near Searchmont, Ontario, was studied. Two plots (P1, 23 ha and P2, 49 ha) were sprayed with an emulsion formulation of fenitrothion at 280 g in 1.5 L per ha using a Cessna 188 aircraft equipped with 4 Micronair® AU3000 atomizers. Kromekote® card/glass plate collection units were placed around the sample trees to determine spray deposit at ground level. Balsam fir and white birch foliage, caged and wild pollinators, moths and wild flower species were collected for deposit assessment. Water samples were collected, at different intervals of time after treatment, from a creek inside the spray plot (P2), and from a nearby river into which the creek drained. All samples were analysed by gas-liquid-chromatography. Droplet analysis on Kromekote cards showed that the mean droplet frequency (droplets/cm 2 ), number and volume median diameters were nearly the same at all sampling sites in both plots. Fenitrothion deposits (in ng/cm2) at mid-crown level of the sample trees were slightly higher on birch leaves than on fir foliage. The tubular chokecheery flowers showed higher deposits than the bell-shaped blueberry flowers. The caged pollinators showed higher fenitrothion concentrations than the wild pollinatorso The insecticide concentration in the creek rose to a maximum of 31.0 ug/L within five min after treatment, but fell to 0.5 μg/L after 24 h. The concentration-time profile showed that nearly half of the initial concentration in the creek water was lost within 21.8 min. In the river water sampled outside the spray area, the post-spray concentration, on average, was 2.2 μg/L.

Assessment of foliar and ground deposits of aminocarb after aerial spraying over conifer forests using two types of application parameters

Experimental observations made in eight aerial spray trials on the inter-relationships between physical properties of two spray mixtures, application parameters, meteorological conditions, drop size spectra, ground deposits and foliar concentrations of aminocarb are described in this paper. In 1981, the spray mixtures were applied using a small aircraft (Cessna 188) equipped with four rotary (Micronair® AU3000) atomizers. In 1982, the mixtures were sprayed using a large aircraft (TBM avenger) fitted with 24 hydraulic (1010 Flatfan Teejet®) nozzles. Spray drops were collected at ground level with sampling cards, and ground deposits were assessed using glass plates. Canopy deposits were determined directly on live foliage. Physical properties measured were: viscosity, surface tension and volatility, In the 1981 study, the drop size spectra of both spray mixtures were narrow and contained small drops with a volume median diameter (D V . 5 ) less than 50 μm. In the 1982 study, the drop size spectra were wide and contained large drops with a D V . 5 greater than 100 μm. The ground deposits were higher in 1982 than those in 1981. Foliar deposits, on the other hand, were similar in both years. Among the three physical properties studied, viscosity and volatility played significant roles on the drop size spectra and ground deposits obtained in 1981; but no similar relationships could be found in 1982.