Fractioning of an ethoxylated soybean oil adjuvant and studies on the potency of the fractions in combination with bromoxynil octanoate and sulfonylurea herbicides
- Publication Type
- Journal contribution (peer reviewed)
- Authors
- Heini, Julia; Walker, Frank; Schöne, Jochen; Mainx, Hans-Georg; Gerhards, Roland
- Year of publication
- 2012
- Published in
- Journal of Plant Diseases and Plant Protection
- Band/Volume
- 119/5
- Page (from - to)
- 208-215
Adjuvants are commonly used to improve the efficacy of pesticides,both as part of formulations or as a separate addition to the spray tank. One such adjuvant is an ethoxylated soybean oil (ESBO). As the chemical composition of ESBO and the fractions mainly responsible for the adjuvant-effect are unknown, the aim of the present study was to elucidate thecomposition of ESBO applying preparative high-performanceliquid chromatography (prep. HPLC) and to evaluate the adjuvant-effectof isolated fractions in comparison to the commercialproduct. By prep. HPLC, four main fractions could bedetermined and isolated. Abutilon theophrasti (velvetleaf) and Zea mays (maize) were used as test species to evaluate theadjuvant effect of isolated fractions or ESBO on the herbicidalefficacy of bromoxynil octanoate, foramsulfuron & iodosulfuron, and technical grade bromoxynil potassium. Experiments were conducted under greenhouse conditions and dry weight of leaves, leaf area, and quantum yield of photosystem II were evaluated as response parameters. Leaf area and dry weight responses showed that there was a tendencytowards late eluting (non-polar) fractions enhancing the efficacyof hydrophilic herbicides to a higher extent than earliereluting (polar) fractions. For example, foramsulfuron &iodosulfuron in combination with the most non-polar fraction resulted in a 61% lower dry weight of velvetleaf compared with the herbicide treatment without adjuvant. The analysis of quantum yield resulted in the lowest values for the treatment with bromoxynil octanoate (BO) mixed with ESBO and foramsulfuron & iodosulfuron (FI) combined with the most polar fraction, respectively. The detection of an active compound within an adjuvant could be a new direction for additive optimisation and, hence, very precise recommendations for herbicide-adjuvant mixtures might be deduced.