Canadian Forest Service Publications
Drop-size spectra and deposits of four Bacillus thuringiensis formulations on simulated and natural fir foliage. 1994. Sundaram A. ASAE 37(1):9-17.
Issued by: Great Lakes Forestry Centre
Catalog ID: 36555
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In aerial spray studies reported in the literature using concentrated aqueous formulations, the segments of drops that remained above the foliar surface were sized after impaction. The drop volume that could have penetrated into thefoliar cuticle was not taken into account. The objectives of the present study were to spray monodispersed drops over naturaland simulated balsam fir needles, to determine drop spreading, to measure the sizes o fdrop segments above the foliage, and to compute the drop volume that penetrated into the foliar surface. Four aqueousformulations of Bacillus thuringiensis var. kurstaki, containing a dye and a chemical tracer [triethyl phosphate (TEP)], were sprayed in a laboratory chamber over balsam fir branches clipped from field-grown trees. Spray was also applied on aluminum fir branches withandwithout a coating oft he cuticular wax extracted from natural fir foliage. Drop-size spectra, drops/cm2, and deposits (ng TEPIcm2 offoliar area, and ng formulation protein/cm2) were assessed on the natural foliage and wax coated aluminum foliage (foliar simulator); but only drops/cm2 and deposits of TEP and protein were measured on the uncoated aluminum foliage. Both natural foliage and foliar simulator received similar drop sizes, drops/cm2, and deposits, but the latter two parameters were higher on the uncoated aluminum foliage. The investigation provided a new method to determine the actual sizes of drops deposited on a foliar simulator. The simulator not only had simila rsize and shape, but also the same surface characteristics. Quantification of protein deposits was also faster on the simulator than on the natural foliage. Keywords. Bacillus thuringiensis formulations, Drop-size spectra, Spray deposit. Protein deposit, Cuticular wax, Balsam fir needle, Foliar simulator.