Residues and residue management continues to be of interest for all in the food supply chain. This is particularly true for growers and suppliers of fruit and vegetables.
In 2007, Bayer CropScience introduced its MiniMizer project as a way of working with growers and suppliers who wanted to reduce residues while maintaining the quality of their produce. Each year we have extended the range of crops and products investigated.
The work was conducted in conjunction with marketing organisations, Norman Collett, Worldwide Fruit and OrchardWorld on four orchards in Kent, and one in Gloucestershire, as well as on our own research farm in Hertfordshire. The trials successfully demonstrated that products such as Calypso and Runner can be used to grow top quality fruit, whilst minimising residues.
In recent years the work has been extended to brassica crops looking at the use of the fungicides Nativo 75WG (trifloxystrobin + tebuconazole) and Rudis (prothioconazole) in both England and Scotland. The data so far suggest that it is the timing of the last application of these fungicides that is the key factor from a residue perspective, rather than the number of times each is applied. This work is continuing with the help of the Allium and Brassica Centre and a major brassica company in Scotland.
With the registration of the novel insecticide Movento (spirotetramat) in 2010 this important new product was added to the research program. Work has concentrated on Brussels sprouts, cabbages and lettuce, and will continue in future years.
The project has deliberately focused on reducing or minimising residues rather than seeking to achieve 'zero' residues or residue-free produce. Whilst the latter may sound attractive, it is not always possible to achieve if, for example, crops are attacked by late season pests or diseases that could threaten crop quality, or even result in significant crop losses, if left untreated.
A further complication is that the definition of 'zero' residues changes with time as improvements are made to the analytical techniques used to measure pesticide residues. Only a couple of years ago the detection level for pesticide residues was generally 0.05 mg/kg, whereas today the current analytical techniques generally detect residues down to a level of 0.01 mg/kg (or 10 parts per billion). There has, therefore, been a five-fold increase in analytical sensitivity in recent years, which greatly increases the possibility of detecting a residue.
Despite this, it is interesting to note that 60% of the food we eat contains no detectable residues (source: Pesticide Residue Committee Annual Report 2009).