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ARS Home » Midwest Area » Wooster, Ohio » Application Technology Research » Research » Publications at this Location » Publication #93971
Title: PERFORMANCE OF OIL-AND WATER-SENSITIVE PAPERS IN SPRAY COVERAGE EVALUATION

Author
item SALYANI, M - UFCREC
item Fox, Robert

Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/8/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: The objective of any spray application is to obtain a uniform coverage of the spray droplets throughout the target canopy. A key in any spray evaluation program therefore, is a reliable, accurate method of measuring spray coverage. One technique that has been used for several years is water-sensitive-paper (WSP). This yellow paper turns bright blue where water drops impact it. A problem with WSP is that the target papers become masses of blue if too many droplets strike the paper, which makes droplet size and coverage analysis impossible. This is the first study that compared WSP collectors with oil-sensitive-paper (OSP). A dilute oil/water mixture was sprayed on citrus trees using nine spray treatments. WSP and OSP targets were collected from 12 positions in and between trees. Spot coverage on WSP and OSP targets were measured with an image system. Results show that OSP targets contained much less overlap and were easily scanned, whereas many WSP targets were completely covered with spots and not measurable. Percent area coverage, mean spot diameter, volume mean diameter and spot density were used to evaluate distribution patterns. Both WSP and OSP were significantly affected by the sprayer treatment and target location. Of the parameters measured, percent area covered appeared to be the most consistent and reliable. Use of oil-sensitive-paper to evaluate differences among spray treatments should be a useful tool for growers, sprayer companies as well as researchers on application technology and plant pest control.

Technical Abstract: Nine spray treatments were applied to plots of orange trees, in a randomized complete block design and four replications. The treatments involved three air-carrier sprayers, operating at different volume rates and ground speeds. Spray mixtures contained a petroleum oil (Sunspray 7E) at a constant rate of 37.5L/ha and water rates of 220 to 3,750 L/ha. The oil-and water-sensitive papers (OSP and WSP) were used as spray targets. The targets were placed at two heights, outside and 0.3 - 0.4 m inside the canopy. At each location, both OSP and WSP were stapled to the upper and lower leaf surfaces of two neighboring leaves. Additional target pairs were also positioned rigidly on target holders, in the gap between two adjacent trees, at two heights and a horizontal top, horizontal bottom, and vertical positions. Sprayed targets were analyzed by an imaging system. The percent area coverage, mean spot diameter, volume mean diameter, and spot density were used to evaluate distribution patterns. There was a substantial variation in distribution patterns of different replicates. Both WSP and OSP patterns were significantly affected by the sprayer treatment and target location. The results were quite variable and none of the target types were found to be suitable for quantitative assessment of spray coverage or droplet size measurement. Among all parameters, the percent area coverage appeared to be the most reliable.