Characterising plant surfaces for spray adhesion and retention

Abstract

A simple measurement of static contact angle of aqueous acetone droplets on surfaces has been developed for characterising leaf surfaces It allows leaves to be compared and grouped by their surface roughness factor and it differentiates between easy difficult and very difficulttowet species This paper describes how the method has been used to survey a large number of plant species including weeds and crops fruit and foliage High contact angles indicate difficulttowet surfaces The quantitative measure of contact angle is a useful tool to predict spray droplet adhesion and rank plant surfaces for retention properties It can also indicate whether surfactant addition is likely to be beneficial for agrochemical sprays targeted at fruit or foliage on different crops Surfactants were most useful for improving spray droplet adhesion and retention on difficulttowet surfaces but results varied with surface wettability surfactant type and concentration and with plant architecture

Effect of cold‐induced changes in physical and chemical leaf properties on the resistance of winter triticale (×Triticosecale) to the fungal pathogen Microdochium nivale

“…In hardened plants, organic substances affecting the hydrophobic and electric properties of leaf surface, such as fats, waxes, cutins, alkaloids, terpenes, glycosides and phenols, were detected by thermal analysis, autofluorescence and spectrophotometry. These compounds are waterproof, increasing surface hydrophobicity, and helping to block the entry of pathogenic fungi (Gaskin et al, 2005;Bhushan & Jung, 2008;Teisala et al, 2011). Hence, data indicating a higher amount and/or stability of hydrophobic molecules in the hardened cv.…”

“…Angles over 120°and width-to-height ratios below 1Á28 indicate that the surface is hydrophobic and very difficult to wet. A surface is superhydrophobic if it has a water contact angle around 150° (Gaskin et al, 2005;Bhushan & Jung, 2008).…”

Potential and actual uses of zeolites in crop protection

“…The droplet size distribution during atomisation is very important because it affects (1) the biological activity and (2) the spray drift (droplets that are too small are prone to drift away to adjacent fields and non-target areas). 46,47 The optimum droplet size depends on the content of the droplet, the amount of active ingredient in the droplet and the type of application, i.e. as an insecticide, a herbicide, a fertiliser, etc.…”

Stemflow production and intrastorm rainfall intensity variation: an experimental analysis using laboratory rainfall simulation

“…It may be that as more widespread moving stemflow films envelop plant surfaces, the capture and retention of small splash droplets is enhanced, so increasing the proportion of incident rain that becomes stemflow. In addition, branch inclination affects the conveyance of water once retention has been achieved (Herwitz, 1987), and also the partitioning of incident drops among the primary pathways of adhesion, bounce, and shatter (Macdonald and McCartney, 1988;Gaskin et al, 2005;Forster et al, 2012). Shatter becomes less important on steeper plant parts (Forster et al, 2012) and this suggests that leaf droop as wetting-up takes place will self-modify subsequent drop adhesion behaviour.…”