L. Sloane

Effects of pure and formulated azadirachtin, a neem‐based biopesticide, on the phytophagous spider mite, Tetranychus urticae koch

Abstract Pure azadirachtin‐A (AZ‐A) and four neem‐based formulations (RH, MO, PT and AT) containing the insecticide isomer were tested for their repellency, toxicity and oviposition deterrence against the phytophagous two‐spotted spider mite (Tetranychus urticae Koch). Mites were placed on treated and untreated aspen (Populus tremuloides Michx.) leaf discs and their fecundity, feeding rate and mortality were assessed. Results indicated that the effects of AZ‐A on T. urticae varied with formulation type and AZ‐A concentration. Significant reductions in feeding and oviposition, which correlated with AZ‐A concentrations, were recorded concomitantly with a significant increase in repellency. Leaf discs treated with increasing concentrations of the formulations showed increased mortality of T. urticae, reduction in the total number of eggs laid, reduced % of eggs hatched and reduced survival of emerged mites. The deterrent and biological effects decreased in the order AT>PT>MO>RH>AZ‐A.

Foliar persistence and residual activity of tebufenozide against spruce budworm larvae

A field study was conducted to investigate the persistence of tebufenozide in white spruce foliage. An aqueous suspension concentrate formulation, RH-5992 2F, was sprayed over single trees at three dosage rates, 35, 70 and 140 g of the active ingredient (AI), in 2.0 litre ha -1 , using ground application equipment. Foliage was collected at different intervals of time up to 64 days after treatment and tebufenozide residues were measured by high-performance liquid chromatography. Foliage was also fed to laboratory-reared 4th- and 6th-instar spruce budworm (Choristoneura fumiferana Clemens). The data indicated that tebufenozide residues in foliage declined with time according to first-order kinetics. The average rate-constant and half-life of disappearance (DT 50 ) were 0.0340 and 20.45 days, respectively. Larval mortality declined gradually, corresponding to the residues, but was still appreciable (49 to 70%) when the larvae were fed with foliage collected 64 days after treatment. The amount of foliage consumed by the larvae decreased when foliar residues of tebufenozide increased, thus indicating anti-feedant activity of the chemical. The LD 50 values for both instars were similar and averaged c.25 ng per insect, but the LD 90 values were significantly lower for 4th-instar than for 6th-instar, at 63.6 and 96.1 ng per insect respectively. This implies that, theoretically, at a foliar concentration of 1.0 μg tebufenozide g -1 foliage (fresh wt), the spruce budworm larva needs to consume 65 to 100 mg of foliage in 10 days to cause mortality in about 90% of a population of the insect.

Formulation selection, and investigation of azadirachtin‐A persistence in some terrestrial and aquatic components of a forest environment

Five commercial formulations of azadirachtin-A (AZ-A) Margosan-O®, Azatin-EC®, Neem-EC®, RH-9999 and Neemix® 4.5, were investigated for their volatilization and washoff potential in laboratory studies. Prior to the investigation, RH-9999 (a wettable powder) was mixed with water to provide an end-use formulation containing 35.6 g AZ-A kg -1 , while the remaining four formulations were investigated without dilution. Volatilization and washoff of AZ-A occurred more from white spruce foliage than from wax-coated glass plates. Neem-EC provided the lowest amount of loss, whereas Margosan-O provided the highest. Physical properties and atomization behaviour of the five formulations indicated that Azatin-EC was highly viscous and caused phase separation in droplets collected on glass plates after atomization in a rotary atomizer. RH-9999, despite its low viscosity, caused phase separation in droplets because of the heterogeneity of the wettable powder formulation. Based on the minimum loss of AZ-A due to volatilization and washoff from spruce foliage, and on the minimum potential for phase separation in droplets after atomization in a rotary atomizer, Neem-EC was considered to be the most appropriate choice for use in field studies to investigate environmental persistence and fate of AZ-A in terrestrial and aquatic matrices of a forest ecosystem. The Neem-EC formulation was sprayed at 40 and 80 g AI ha -1 over single spruce trees and on litter and soil plots selected in a mixed-wood boreal forest in Ontario, Canada. In addition, outdoor aquaria containing stream water and sediment were also fortified with the formulation at 400 and 800 g AI ha -1 . Persistence of AZ-A was evaluated using one-year-old spruce needles, current-year shoots, spruce bark, litter, soil, stream water and sediment. The duration of persistence varied from 3 to 6 days in terrestrial matrices, whereas it ranged from 8 to 13 days in water, and 2 to 3 days in sediment. The half-life (DT 50 ) values ranged from 10.7 h (for soil) to 71.6 h (for spruce bark) at the lower dosage rate, and from 18.8 h (for litter) to 76.2 h (for bark) at the higher dosage rate. The DT 50 value for stream water was about 35 h regardless of the dosage rate applied. The data indicated that AZ-A was appreciably labile and short-lived in different forestry matrices, with low DT 50 values.

Kinetics of Azadirachtin Hydrolysis in Model Aquatic Systems by High-Performance Liquid Chromatography

Abstract The hydrolysis of azadirachtin-A isomer (AZ-A) was studied at 20°C in the dark in buffered distilled water at pH 4, 7 and 10, and in unbuffered sterilized and unsterilized pond water. Individual solutions were fortified in triplicate with pure AZ-A and formulated AZ-A separately. Hydrolysis of AZ-A in pond water was studied by using pure AZ-A only. At pH 10, AZ-A fortified either in pure form or as formulation, was hydrolysed rapidly and the DT50 was only about 2 h. At pH 4, the DT50 values for the pure and formulated AZ-A were 19.2 and 38.3 d, respectively, indicating that the chemical is relatively stable in acidic medium. The stability was diminished at pH 7 and the corresponding DT50 values were 12.9 and 30.5 d. The data show that the hydrolysis of AZ-A is greatly influenced by pH in the order pH 10 >>> pH 7 > pH 4. The differences in DT50 values between pure AZ-A and formulated AZ-A, at pH 4 and 7, suggest that hydrolysis is considerably retarded by the surfactants in the formulation. The av...

Dissipation kinetics of azadirachtin in some forest matrices and its systemic translocation in conifers for spruce budworm control

Abstract Field microcosm studies were conducted to investigate the deposition, persistence, translocation and bioactivity of the botanical insecticide azadirachtin‐A (AZ‐A) in young spruce trees. The deposition and persistence of AZ‐A in aspen foliage, forest soil and litter were also studied. AZ‐A residues in the different matrices were monitored at intervals of time after spray application of Neemix® 4.5 formulation at 100 g AZ‐A in 2.3 L/ha. The dissipation half‐lives in the matrices ranged from 16.9 to 33.6 h. AZ‐A was translocated and concentrated in the growing parts (especially the shoots) of spruce trees, after treatment by trunk injection (Tl), basal bark painting (BBP) and foliar painting (FP) of the Neemix 4.5 formulation. Systemically translocated and accumulated AZ‐A residues in the shoots after Tl and FP were found to be effective against spruce budworm (Choristoneura fumiferana Clemens.) larvae. Results suggest that Tl may be a useful way of using neem insecticide to protect high value tree...

Spray deposition and persistence of a Bacillus thuringiensis formulation (Foray® 76B) on spruce foliage, following aerial application over a northern ontario forest

Abstract A commercial formulation of Bacillus thuringiensis Berliner subspp. kurstaki, Foray® 76B, was sprayed aerially at a dosage rate of 30 BIU in 1.5 L per ha, over a 500‐ha block in a mixed spruce‐fir forest in northern Ontario, Canada, using two fixed‐wing aircrafts equipped with rotary atomizers. Droplet size spectra were determined on Kromekote® cards at ground level, and spray deposit recovery was assessed on glass plates. Initial deposits and persistence of different components of the formulation were determined on canopy foliage by bioassay using spruce budworm (Choristoneura fumiferana Clem.) larvae as the indicator species, and by different quantification techniques that were newly developed in this study. For quantification of foliar deposits, the total protein content was determined and foliar residues were expressed in ng per g foliage (fresh weight). Foliar extracts were acidified to precipitate the protein. The supernatant was subjected sequentially to n‐hexane and n‐octanol extraction, ...

Adsorption and desorption kinetics of diflubenzuron and fenitrothion in two different boreal forest soils

Abstract Adsorption and desorption of two insecticides, diflubenzuron (DFB) and fenitrothion (FEN), were studied by batch equilibrium method under laboratory conditions (pH 5.5, 20°C), using an organic soil (soil 1) and a silty clay loam soil (soil 2), collected from a boreal forest in northern Ontario, Canada. Adsorption parameters were calculated using the linear, Freundlich and Langmuir equations. Maximum amount adsorbed and the time required for maximum adsorption of DFB were 88 μg/g and 18 h (soil 1), and 73 μg/g and 24 h (soil 2), respectively. Corresponding values for FEN were 92 μg/g (soil 1) and 81 μg/g (soil 2), and maximum adsorption time for both soils was 30 h. DFB was more strongly adsorbed to both soils compared to FEN, however between the two soils, soil 1 showed stronger affinity for the chemicals than soil 2. The KD, KF and n values corroborated these findings. The Langmuir model showed deviation, probably due to heterogeneity of the soil surface and multi‐layer adsorption. Desorption st...

Liquid Chromatographic Assay for the Separation of Single- and Double-Stranded DNA by Using Uv and UV Diode-Array Detectors and Hydroxylapatite Column

Abstract A high-performance liquid chromatographic (HPLC) method, using UV and UV diodearray (DA) detection, is reported for the separation of single-stranded (s.s.) and double-stranded (d.s.) DNA molecules. Commercially available calf thymus DNA was used as the standard, to develop and optimize necessary analytical procedures and chromatographic parameters. Bio-Gel® hydroxylapatite was used as the column packing and the sorbed polynucleotides on the column matrix were separated by using an ionic strength gradient system consisting of phosphate buffer at pH 6.8. The stationary phase was stable and proved sufficiently reliable in the separation and resolution of s.s. and d.s. DNA molecules in the standard. Pointedly, the DA detector was more sensitive to the analytes than the UV detector. The response of both detectors was higher for the s.s. DNA compared to the d.s. DNA. Minimum quantification limits (MQL) for the s.s. DNA molecules by the DA and UV detectors were, respectively, 0.10 and 0.50 μ. in 10 μ i...

Persistence of bacillus thuringiensis deposits in oak foliage, after aerial application of foray® 48b using rotary and pressure atomizers

Abstract A commercial formulation of Bacillus thuringiensis var. kurstaki (Btk), Foray® 48B, was sprayed aerially over blocks selected in a hardwood forest in the USA at the rate of 90 billion international units in 7.0 L/ha, using a helicopter and a fixed‐wing aircraft, each fitted with pressure or rotary cage atomizers. Droplet size spectra were assessed on foliage using two new parameters, viz., droplet‐spot number median diameter (S‐DN.5) and protein mass median diameter (S‐DM.5). The data indicated that when rotary cage atomizers were used, the droplet spectra were narrow with smaller S‐DN.5 and S‐DM.5 values, than when pressure atomizers were used. The protein mass deposits corresponded with the droplet sizes, i.e., the larger the droplet sizes, the greater the deposits. The initial bioactivity did not correspond with the deposits, because the greater the deposits the lower the activity. Persistence of bioactivity also showed irregularities, indicating the role of environmental transformation of for...

Effect of tracer dyes on initial deposits and persistence of bacillus thuringiensis subsp. kurstaki toxin after application of two commercial formulations onto spruce trees

Abstract The effect of two tracer dyes [Erio Acid Red (EAR) and Acid Black 48 (AB‐48)] on initial deposits and persistence of Bacillus thuringiensis subsp. kurstaki (Btk) toxin (delta‐endotoxin) was studied after spraying two commercial formulations, Foray® 48B and Foray® 76B, over potted white spruce [Picea glauca (Moench) Voss] seedlings, at a dosage rate of 30 billion international units (BIU) per ha. Spray was applied using a spinning disc atomizer calibrated to deliver droplet sizes similar to those utilized in ultra‐low‐volume (ULV) treatments in operational insect control programs. The sprayed seedlings were left outdoors at the Sault Ste. Marie laboratory for 18 days under natural conditions of sunlight, wind and rainfall. Initial deposits and persistence of delta‐endotoxin protein in spruce foliage were determined by immunoassay [enzyme linked immunosorbent assay (ELISA)] quantification of the delta‐endotoxin. The total protein (inactive plus active) and delta‐endotoxin (active protein) concentra...