Surfactant-induced deposit structures in relation to the biological efficacy of glyphosate on easy- and difficult-to-wet weed species.
BACKGROUND
Typical active ingredient (AI) residue patterns are formed during droplet drying on plant surfaces owing to the interaction of spray solution characteristics and leaf micromorphology. Currently, comparatively little is known about the influence of AI deposit patterns within a spray droplet residue area on the penetration and biological efficacy of glyphosate. A scanning electron microscope with energy dispersive X-ray microanalysis has been used to characterise residue patterns and to quantify the area ultimately covered by glyphosate within the droplet spread area.


RESULTS
The easy-to-wet weed species Stellaria media L. and Viola arvensis L., as well as the difficult-to-wet Chenopodium album L. and Setaria viridis L., differing in their surface micromorphology, have been used. Rapeseed oil ethoxylates (RSO 5 or RSO 60) were added to glyphosate solutions to provide different droplet spread areas. Addition of RSO 5 enhanced droplet spread area more than RSO 60, and both caused distinct glyphosate residue patterns. The biological efficacy of treatment solutions showed no significant correlation with the area ultimately covered by glyphosate.


CONCLUSIONS
The results have implications on herbicide uptake models. This study shows that droplet spread area does not correspond to the area ultimately covered by glyphosate, and that the latter does not affect glyphosate phytotoxicity.
Institute of Crop Science and Resource Conservation-Horticultural Science, University of Bonn, Auf dem Huegel 6, 53121 Bonn, Germany.
Thorsten
T
Kraemer
Mauricio
M
Hunsche
Georg
G
Noga
D027462:Chenopodium / Q000187:drug effects*; D005229:Fatty Acids, Monounsaturated; D005998:Glycine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology; D006540:Herbicides / Q000737:chemistry / Q000494:pharmacology; D018515:Plant Leaves / Q000187:drug effects; D010938:Plant Oils / Q000494:pharmacology; D000074262:Rapeseed Oil; D032983:Setaria Plant / Q000187:drug effects*; D012996:Solutions; D013223:Statistics as Topic; D029752:Stellaria / Q000187:drug effects*; D013499:Surface Properties / Q000187:drug effects; D013501:Surface-Active Agents / Q000494:pharmacology*; D032413:Viola / Q000187:drug effects*; D000097797:Glyphosate
D005229:Fatty Acids, Monounsaturated; D005998:Glycine; D006540:Herbicides; D010938:Plant Oils; D000074262:Rapeseed Oil; D012996:Solutions; D013501:Surface-Active Agents; D000097797:Glyphosate