Formulation selection, and investigation of azadirachtin-A persistence in some terrestrial and aquatic components of a forest environment
✍ Scribed by Sundaram, Kanth M. S.; Sundaram, Alam; Curry, Johanna; Sloane, Linda
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 307 KB
- Volume
- 51
- Category
- Article
- ISSN
- 1526-498X
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✦ Synopsis
Five commercial formulations of azadirachtin-A (AZ-A) Margosan-RH-9999 and 4.5, were investigated for O}, Azatin-EC}, Neem-EC}, Neemix} their volatilization and washo † potential in laboratory studies. Prior to the investigation, RH-9999 (a wettable powder) was mixed with water to provide an end-use formulation containing 35É6 g AZ-A kg~1, while the remaining four formulations were investigated without dilution. Volatilization and washo † 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 Ðve 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 washo † 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 Ðeld 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 fortiÐed with the formulation at 400 and 800 g AI ha~1. Persistence of AZ-A was evaluated using one-year-old spruce needles, currentyear 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 values (DT 50 ) ranged from 10É7 h (for soil) to 71É6 h (for spruce bark) at the lower dosage rate, and from 18É8 h (for litter) to 76É2 h (for bark) at the higher dosage rate. The value for stream water was about 35 h regardless of the dosage rate DT 50 applied. The data indicated that AZ-A was appreciably labile and short-lived in di †erent forestry matrices, with low values. DT 50