TY  - THES
T1  - Studies on the efficacy, composition and mode of action of an ethoxylated soybean oil adjuvant for herbicides
A1  - Heini,Julia
Y1  - 2013/01/28
N2  - The potential of an ethoxylated soybean oil adjuvant ? Agnique® SBO 10 ? to increase the efficacy of different herbicides was investigated in the present thesis. Furthermore, Agnique® SBO 10 was fractioned by preparative High-Performance Liquid Chromatography (prep. HPLC) to elucidate the composition of the ethoxylated soybean oil (ESBO). In addition, experiments with fluorescein-labelled Agnique® SBO 10 were conducted to evaluate the fate of modified seed oil adjuvants on the leaf surface. 
The efficacy of many herbicides can be increased by adding adjuvants to the spray solution. Adjuvants, in particular surfactants, are able to increase the foliar uptake of active ingredients for example, by enhancing the retention of spray droplets on cuticles, penetration and absorption into leaf tissue. Agnique® SBO 10 belongs to a group of environmental friendly surfactant containing ten ethylene oxide units. Modified seed or vegetable oils are biodegradable and are proposed to be as effective as petroleum oils. These facts make them very interesting for the usage as adjuvants for agrochemicals. To evaluate the potency of Agnique® SBO 10 dose-response studies were accomplished. Results showed that sulfosulfuron, topramezone, and foramsulfuron & iodosulfuron did not control velvetleaf (Abutilon theophrasti Medik.) sufficiently when they were applied without adjuvant. Agnique® SBO 10 acted 2-fold better compared to the recommended adjuvants. Thus, Agnique® SBO 10 could present an alternative adjuvant for a widespread use. These results show, that a certain adjuvant has the potential to increase the efficacy of a herbicide to its maximum. However, for the user it is not easy to choose a proper adjuvant of the broad range of available products. Thus, integrating additives into pesticide formulations is desirable. Due to the fact, that Agnique® SBO 10 is a huge and complex product it cannot be included into a formulation. For this reason, an experiment was accomplished dividing Agnique® SBO 10 into four fractions by using preparative HPLC. These four fractions were isolated of Agnique® SBO 10 and tested in combination with commercially formulated herbicides (foramsulfuron & iodosulfuron and bromoxynil octanoate) and a technical grade bromoxynil product. The aim was to find a fraction with a higher potential compared to Agnique® SBO 10 to be used as low-molecular adjuvant. The herbicide-fraction mixtures were applied as droplets with a pipette on velvetleaf leaves. Dry weight and leaf area measurements of test plants demonstrated that the efficacy of foramsulfuron & iodosulfuron and the technical bromoxynil was increased with decreasing polarity of isolated fractions of Agnique® SBO 10, whereas the efficiency of bromoxynil octanoate was tendentially enhanced adding more polar fractions to the herbicide solution. Again, it was demonstrated that the herbicide?s efficacy is strongly dependent of the adjuvant/fractions.
Though a lot of research was conducted to confirm the positive effect of adjuvants on herbicides, their mode of action is still not completely clear. Because modified vegetable oils are complex compounds, a radioactive labelling is not easy. Therefore, in this study Agnique® SBO 10 was labelled with fluorescein to investigate, whether Agnique® SBO 10 remains on the leaf surface, accumulates in the cuticle or even penetrates into the underlying plant tissue. Fluorescein-labelled Agnique® SBO 10 (AF) was applied to one leaf of the test species velvetleaf, wild mustard and sugar beet. At different time intervals, treated leaves were harvested and rinsed with different washing solutions (deionised water, methanol/water and chloroform). The washed leaves and the respective washing solutions were processed separately and analyzed with HPLC coupled with an UV detector. Results lead to the assumption that AF might have been passed through the cuticle. However, AF is not expected to be very mobile because it is lipophilic and electrically neutral. If there was a penetration through the cuticle, an enzymatic metabolisation of Agnique® SBO 10 into fatty acids and ethoxylated glycerol is likely to occur.
With this thesis the herbicide-enhancing effect of Agnique® SBO 10 was confirmed. Furthermore, a new approach for the design of optimized adjuvants for precise herbicide-adjuvant mixtures was presented. Though a lot of research has to be conducted to elucidate the mode of action of adjuvants, this study gives an approach to investigate the behaviour of foliar applied adjuvants.
KW  - Adjuvans
KW  - Herbizid
KW  - Sojabohnenöl
CY  - Hohenheim
PB  - Kommunikations-, Informations- und Medienzentrum der Universität Hohenheim
AD  - Garbenstr. 15, 70593 Stuttgart
UR  - http://opus.uni-hohenheim.de/volltexte/2013/795
ER  -