Aerial spray deposition on mesquite
1992
Bouse, L.F. | Whisenant, S.G. | Carlton, J.B.
Deposition of aerially applied herbicide spray was measured on leaves, soda (drinking) straws, and water-sensitive cards in the upper and lower parts of honey mesquite plants for spray mixture application rates of 18.7, 37.4, and 74.8 L/ha (2, 4, and 8 gal/ac) and droplet spectrums having 325 +/- 25, 475 +/- 25 and 625 +/- 25 micrometers D(v0.5) (volume median diameter). Disc and disc-core nozzles were used to produce the different droplet spectrums. Two types of tubular nozzles (10-762 micrometers inside dia tubes each), included in part of the experiments, produced D(v0.5) of 295 and 311 micrometers at 18.7 L/ha and 330 and 352 micrometers at 37.4 L/ha. Results generally indicated that herbicide active ingredient deposits were highest for the 18.7 L/ha mixture application rate, with some exceptions for which the 325 micrometers D(v0.5) droplets and 74.8 L/ha mixture application rate resulted in higher deposits on plant leaves. No consistent trends were found for the effect of droplet size on the deposit on plant leaves; however, the smaller droplets tended to produce the highest deposits on soda straws. Droplet density (droplets/cm2) on water-sensitive cards was greatest for small droplets and decreased with an increase in droplet size. Droplet density increased with an increase in mixture application rate for most experiments, but not in direct proportion to mixture application rate increase. The tubular nozzles generally produced spray deposits similar to those for the 325 +/- 25 and 475 +/- 25 micrometers D(v0.5) sprays. Data on the relative mortality of honey mesquite indicated that larger droplet sizes require increased mixture application rates for greatest efficacy.
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