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(R), A zatin-EC(R), Neem-EC(R), RH-9999 and Neemix(R) 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 dilu tion, Volatilization and washoff of AZ-A occurred more from white spru ce foliage than from wax-coated glass plates. Neem-EC provided the low est amount of loss, whereas Margosan-O provided the highest. Physical properties and atomization behaviour of the five formulations indicate d that Azatin-EC was highly viscous and caused phase separation in dro plets collected on glass plates after atomization in a rotary atomizer . RH-9999, despite its low viscosity, caused phase separation in dropl ets because of the heterogeneity of the wettable powder formulation. B ased on the minimum loss of AZ-A due to volatilization and washoff fro m spruce foliage, and on the minimum potential for phase separation in droplets after atomization in a rotary atomizer, Neem-EC was consider ed to he the most appropriate choice for use in field studies to inves tigate environmental persistence and fate of AZ-A in terrestrial and a quatic matrices of a forest ecosystem. The Neem-EC formulation was spr ayed at 40 and 80 g AI ha(-1) over single spruce trees and on litter a nd soil plots selected in a mixed-wood boreal forest in Ontario, Canad a. In addition, outdoor aquaria containing stream water and sediment w ere also fortified with the formulation at 400 and 800 g AI ha(-1). Pe rsistence of AZ-A was evaluated using one-year-old spruce needles, cur rent-year shoots, spruce bark, litter, soil, stream water and sediment . The duration of persistence varied from 3 to 6 days in terrestrial m atrices, whereas it ranged from 8 to 13 days in water, and 2 to 3 days in sediment. The half-life (DT50) 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 DT5 0 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 DT50 values.