​A team from the University of Manchester, ISIS and the agriculture company Syngenta have used a combination of analytical techniques to study the efficiency of pesticides in the development of agri-sprays, commonly used in the agricultural industry.

Increasing pesticide efficiency would not only reduce costs, but also damage to non-target plants, the ecology and the living environment. Additives, such as non-ionic surfactants, are commonly used in pesticides such as agri-sprays to maximise pesticide efficiency and enhance pesticide uptake.

Surfactants decrease the surface tension of the droplets in the agri-spray, increasing the contacting area on the spraying surface. They also absorb onto, and penetrate into, the plant surface, creating a pathway for pesticides to diffuse into the plant itself. As a large proportion of pesticides have an extremely low water solubility, surfactants can also be used to improve their mobility by forming micelles, which act as capsules containing the pesticide.

When sprayed, the micelles come into contact with the thin wax layer on the outer surface of the plant. These waxes are predominantly hydrophobic, but contain polar alcohol and ester end groups that offer some weak hydrophilicity. Their amphiphilic nature may explain why the micelles take up wax molecules when they land on the plant surface. However, there is little knowledge about the exact molecular processes involved, and the impact on the pesticides when this happens.

Combining techniques such as proton nuclear magnetic resonance (H-NMR) and cryogenic transmission electron microscopy (Cryo-TEM) with SANS techniques using LOQ at ISIS, the research group examined the changes in micelles saturated with fungicide before and after wax solubilisation. Their study confirmed that the micelle nanostructures are heavily influenced by wax solubilisation and pesticide release. These initial findings have shown that agrochemical sprays are capable of dissolving the waxy layers on leaves, which may trigger surfactant micelles to release pesticides.

"ISIS provides users with state of the art instruments that can provide us, as researchers, methods to probe deeper into our pesticide delivery and uptake system", said Xuzhi Hu, from the University of Manchester. “Our research is driven by both academic and industrial relevance which is enabled by the ISIS research facility; their incredibly helpful support staff and world leading experts provide a service that is second to none."​ 

Instrument: LOQ