David Senaeve

Influence of adjuvants on the dissipation of fenpropimorph, pyrimethanil, chlorpyrifos and lindane on the solid/gas interface

The use of pesticides is an integral part of modern agriculture and contributes to the productivity and the quality of the cultivated crop. However, use of pesticides imposes a huge burden on the environment. Volatilisation of pesticides contaminates the environment, affects nearby crops, bystanders and residents but research to mitigate this environmental contamination remains scarce. In this study, the use of adjuvants to reduce the volatilisation and mitigate the environmental contamination was investigated. Dissipation of fenpropimorph, pyrimethanil, chlorpyrifos-ethyl and lindane as pure active ingredient, formulated by different adjuvants and in a commercial formulation were studied. An empirical model assuming exponential decay of the volatilisation rate was used to calculate the volatilisation. In 48 h, up to 90% of the pure fenpropimorph and lindane volatilised. Addition of adjuvants was shown to reduce the volatilisation of pesticides by up to 80%. Commercial formulation was able to reduce the volatilisation of pyrimethanil but the formulation of fenpropimorph had no effect on its volatilisation.

Multi-residue determination and ecological risk assessment of pesticides in the lakes of Rwanda

BACKGROUND To boost agricultural productivity for both domestic and export purposes, agricultural inputs such as pesticides are being promoted in Rwanda. Even though the use of pesticides is important for agriculture, their residues eventually end up in different environmental compartments and may negatively affect the environment. The purpose of this study was to determine the level of knowledge and awareness of the smallholder farmers towards the use of pesticides in Rwanda and to evaluate the ecological risks of pesticides in the surface water and in the vertical profile of Lake Kivu. RESULTS Based on the collected data, a method to monitor 33 currently used pesticides was developed. No contamination of the lower water layer was found, indicating that the groundwater that flows into Lake Kivu has not been polluted. Of the pesticides in the surface water, malathion exceeded the risk thresholds and posed a risk towards arthropods. CONCLUSION The results of this study show that there is a lack of farmers awareness towards the hazards of pesticides when working with these compounds. Farmers in Rwanda are in need of specialised stewardship for pesticide application training and guiding services. Surface water has been contaminated with malathion, metalaxyl and carbendazim which were the most used pesticides by the farmers in the environment.

Formulation approaches to reduce post-application pesticide volatilisation from glass surfaces

Volatilisation is one of the main pathways for pesticide emission to the atmosphere. While formulation strategies and adjuvants are known to affect the fate of active ingredient, no general volatilisation reducing guidelines exist for formulation purposes. Moreover, as limited information on formulation effects is available, current pesticide fate models lack parameters characterising reduction of active ingredient volatilisation. The objective of this study was to investigate the volatilisation reducing potential of formulation types and adjuvants, and to propose an effective vapour pressure for pesticide fate modelling. Several formulations of fenpropimorph, pyrimethanil and tebuconazole were produced and tested in a wind tunnel to evaluate the effect of formulation on active ingredient volatilisation. Produced emulsifiable concentrates with high volatile solvents did not offer any reduction in volatilisation, while the low volatile solvent reduced the volatilisation of pyrimethanil and fenpropimorph with 79.2 and 52.9%, respectively. The microemulsion reduced the volatilisation of fenpropimorph, pyrimethanil and tebuconazole with 57.6, 57.8 and 49.8%, respectively. High surfactant-active ingredient ratios (100:1) reduced the volatilisation of applied amount of pyrimethanil with 50%, on average. The effective vapour pressure of pyrimethanil formulated as a commercial available suspension concentrate was reduced by 33.8%. The commercial available emulsifiable concentrate did not reduce volatilisation of fenpropimorph. Effective vapour pressures of formulated fenpropimorph and pyrimethanil were determined and showed a high correlation with the amount volatilised within 48h. The saturated vapour pressure is useful when comparing the volatility of active ingredients, but effective vapour pressures are more appropriate to be used in pesticide fate models.

Pesticides residue analysis in yam from selected markets across Ghana and Belgium: an evaluation of the QUECHERS method

BackgroundIn recent years, concerns have been raised in Ghana regarding the use of pesticides in yamproduction to the extent that it is feared that pesticides residues may be found in the yam tuber which isconsumed by many Ghanaians. This present study, therefore, was designed to assess the level of pesticides residues in yam bought from across Ghanaian markets i.e. production for local consumption and from Belgium grocery shops (export production from Ghana) using the Quick, Easy, Cheap, Efficient, Rugged and Safe (QuEChERS) method coupled with LC-MS/MS. A total of 180 yam samples, including 150 from Ghana and 30 from Belgium were collected and pesticides residues were analyzed using a multi-residue method.ResultsA total of 25 pesticides were screened in the yam samples and 11 of them were detected. Theresults indicated that about 46% of the samples contained one or more of the 11 detected pesticides in arange of 0.000014 mg/kg up to 0.0146 mg/kg. The three most detected pesticides in this study were fenpropimorph, cadusafos and fenitrothion, occurring in 179, 171 and 126 samples respectively. All the detected pesticides were below their respective EU maximum residue limits (MRL).ConclusionBy these results, it can be said that, the residues of the monitored pesticides found in yam arevery low and are unlikely to pose a negative human health effect.