Water-sensitive Cards Research Articles

Aerial Spray Deposition on Mesquite

Abstract 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 32525, 47525 and 62525 m Dv0.5 (volume median diameter). Disc and disc-core nozzles were used to produce the different droplet spectrums. Two types of tubular nozzles (10762 m inside dia tubes each), included in part of the experiments, produced Dv0.5 of 295 and 311 m at 18.7 L/ha and 330 and 352 m 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 m Dv0.5 droplets and 74.8 L/ha mixture application rate resulted in higher deposits on plant leaves.

Spatial Distribution of Spray Deposition from an Air-Carrier Sprayer

ABSTRACT An air-carrier, orchard sprayer was modified by segmenting the nozzle manifolds on each side into three sub-manifolds. Each sub-manifold represented the top, middle or bottom portion of the sprayer outlet. Spray deposition from each sub-manifold was quantified using water sensitive cards placed on vertical poles. Tests were conducted in both the presence and absence of tree foliage. The presence of tree foliage was found to substantially alter the deposition patterns from those found in the non-foliage tests. Overall, greatest spray deposition was achieved by the bottom manifold. At locations greater than 1.5 m outward from the sprayer and below 2 m in height, spray deposition from the top manifold was extremely poor.

Differential Mortaiity Response of Lepidopteran Defoliators to Insecticides Deposited within Three Strata of Wide- and Narrow-Row Soybeans

Field studies were conducted at two locations within Mississippi to determine the efficacy of aerially applied insecticides within the canopies of wide- and narrow-row soybeans. Water-sensitive cards were placed at three locations within the two canopy types to monitor physical penetration of insecticides in terms of droplets per square centimeter and mean percentage of coverage of the foliage. Estimates of mortality for the soybean looper, Pseudoplusia includens (Walker), in central Mississippi, and for the soybean looper, velvet bean caterpillar, Anticarsia gemmatalis Hubner, and green cloverworm, Plathypena scabra (F.), in south Mississippi were also obtained at three vertical strata. Permethrin (central Mississippi) or methyl parathion (south Mississippi) was applied to both canopies via fixed-wing aircraft and plots were sampled on four postapplication dates. Data suggest that the degree of larva mortality from insecticides differs between row-spacing systems at each vertical stratum. In general, narrow row widths reduced the overall efficacy of an insecticide, but the magnitude of the difference was dependent on the target species. These data are significantly correlated with data on physical penetration of the insecticide, but a great deal of variation is left unexplained. Results of these experiments may assist growers and applicators who have experienced poor control from materials known to be efficacious.

Effects of Soybean Row Spacing on Spray Penetration and Efficacy of Insecticides Applied with Aerial and Ground Equipment

Kromecote® or water-sensitive cards were placed at three or four vertical levels within the canopy of wide (96.5–101.1 cm) and narrow (17.8–25.4 cm) rows of soybeans, Glycine max (L.) Merrill, to measure spray penetration and droplet characteristics of insecticides applied with aerial or ground equipment. Larval mortality data were used to measure the efficacy of the insecticides at three vertical strata within the two row-spacing systems. The size of the droplets deposited was generally smaller within all levels of the narrow-row canopy compared to the wide-row canopy. The total number of drops per cm2 and mean percentage of coverage was reduced in the narrow-row spacing compared to the wide-row spacing, but only within the median one-third of the canopy. Similarly, the percentage of larval mortality was reduced within the median one-third of the narrow-row plots compared to the wide-row plots at the same level. The variable combination of drops per cm2 and number median diameter was significantly correlated ( R = 0.6535) with the percentage of reductions of lepidopterous larval populations of the soybean looper, Pseudoplusia includens (Walker), velvetbean caterpillar, Anticarsia gemmatalis Hubner, and green cloverworm, Plathypena scabra (Fab.).