FOLIAR SPRAY BANDING CHARACTERISTICS

Abstract

Foliar spray banding was explored as a means of reducing pesticide use compared to broadcast applications.Various geometric spray patterns and delivery angles of foliar spray bands were investigated to increase spray deposits ina crop row at a constant spray rate of 94 L/ha. Wind-free laboratory results indicated that a banded application using three65. hollow-cone nozzles, with a laser-measured volume median diameter (VMD) of 110 .m, resulted in the highest (p = 0.05)upper canopy coverage of water-sensitive paper (WSP) of 37%, compared to 31% for a broadcast, 80. flat-fan application(VMD = 152 .m). However, the fore-aft trajectory created by a twin-orifice nozzle (VMD = 135 .m) resulted in less uppercanopy deposit and did not increase deposit in the lower canopy. No statistical differences were observed in lower canopyWSP coverage. Cumulative volume distributions (CVD) of deposit droplet spectra in the upper and lower canopy indicatedthat large droplets were deposited on WSP in the lower canopy. Field test results indicated that the broadcast, 80. flat-fannozzle produced the numerically highest malathion residues of 7.5 ng/cm2 on leaf tops, but this was not statistically different(p = 0.05) from a banded 40. flat-fan nozzle application. Banded twin-orifice and three-nozzle hollow-cone treatmentsproduced the statistically lowest (p = 0.05) leaf-top residues of <3 ng/cm2. No significant (p = 0.05) differences were observedin leaf bottom residues and boll weevil mortality. In summary, downward-pointed sprays produced the greatest leaf-topresidue levels under field conditions with a weak crosswind. Banded, narrow-angle (40.) flat-fan nozzles resulted in moredeposit than a three-nozzle hollow-cone nozzle arrangement in the field. Thus, light wind conditions appeared to negate anyadvantages offered by multiple geometric spray patterns and delivery angles.