Herbicide Dispersal Patterns: HI. as a Function of Formulation

Abstract

The distribution patterns of several herbicide formulations sprayed on adaxial leaf surfaces were determined using scanning electron microscopy coupled with cathodoluminescence and x-ray microanalysis. The sodium and amine salts of MCPA {[(4-chloro-o-tolyl) oxy] acetic acid} sprayed on sugar beet (Beta vulgarisL.) leaves appeared as discrete deposits above the anticlinal cell walls that represented the location of spray drops that adhered to the leaf. When the sodium salt was applied to bermudagrass [Cynodon dactylon(L.) Pers.], the pattern of distribution was the same; however, each deposit was significantly smaller. The iso-octyl ester of MCPA coalesced into numerous, small, thick deposits on the cuticle of sugar beet leaves. The distribution of a wettable powder formulation of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino-s-triazine] appeared as uniform deposits over the anticlinal and periclinal cell walls that represented the location of aqueous spray drops after application. When a flowable formulation of atrazine was applied, there was a significant preferential accumulation of the herbicide at the edges of the separate deposits. One commercial formulation of propanil (3′,4′-dichloropropionanilide) yielded deposits that were crystalline, one that was partially crystalline, and one that was noncrystalline.