The effect of formulation composition and adjuvant type on difenoconazole dislodgeable foliar residue

Abstract

Rigorous risk assessments for those exposed to pesticides are carried out to satisfy crop protection regulatory requirements. Non-dietary risk assessments involve estimating the amount of residue which can be transferred from plant foliage to the skin or clothes, known as dislodgeable foliar residues (DFRs). DFR data are less available than crop residue data as studies are costly and limited by seasonality. European regulatory authorities are reticent to allow extrapolation of study data to different scenarios as the contributory factors have hitherto been poorly identified. This study is the first to use a new laboratory DFR method to investigate how one such factor, pesticide formulation, may affect DFR on a variety of crops. The study used the active substance difenoconazole as both an emulsifiable concentrate (EC 10%) and a wettable powder (WP 10%) with and without adjuvants (Tween 20 and organophosphate tris(2-ethylhexyl)phosphate TEHP) on tomato, French bean and oilseed rape. A comparable DFR% was retained from the WP and EC formulation on most crops except for tomato, where lower DFR% was retained in the case of WP (39 ± 4.7%) compared to EC (60 ± 1.2%). No significant effect of adjuvant addition was observed for either formulation except when mixing TEHP (0.1% w/v) to the EC 10% on French bean, resulting in 8% DFR reduction compared to the EC formulation alone. This research demonstrates the value of a unique DFR laboratory technique in investigating the importance of the formulation and in-tank adjuvants as factors that affect DFR.

Keywords:

• Dislodgeable foliar residue
• non-dietary risk assessment
• factors that affect DFR
• formulation
• difenoconazole
• DFR laboratory technique

Acknowledgement

Authors would like to thank the University of Hertfordshire Knowledge Exchange Program (HKEP) and Syngenta, UK for funding this project as well as providing the data used in this project.

Disclosure statement

The authors confirm that the data supporting the findings of this study are available within the article.

Data availability statement

The authors confirm that the data supporting the findings of this study are available within the article and the Appendix.

Additional information

Funding

The authors also confirm that this work was supported by Funds provided by the University of Hertfordshire knowledge Exchange Program (HKEP) in collaboration with Syngenta, UK.