Phytosanitary products, currently described within the European Union using the acronym PPPs (Plant Protection Products), enjoy a central role in the supply and value chains of Fruits and Vegetable produce. In this brief article we will focus on what is most relevant to these chains, post-harvest fungicides. We will review their current role in postharvest management and the possible evolution of their use in the future.
It is generally accepted that fungicides and fungistatics for post-harvest use are very necessary to avoid decay in the supply chains of citrus fruits, bananas, stone fruits and others, particularly in the commercialization of produce from other continents and for the making up of prepackaged sales units (nets, Girsacs, trays, etc.) with up to 30 or more units at their place of origin.
If such products were not used to mitigate losses from decay, the food waste between origin and consumer would be enormous. As a case in point, one retailer carried out a trial marketing citrus fruit “directly from the field” with catastrophic results, since citrus fruits are the fruit with the greatest tendency to deteriorate, only surpassed by varieties of strawberry.
Currently, there are five postharvest fungicides in use, which can be used legally in practically the entire world: Fludioxonil, Imazalil, Orthophenylphenol, Pyrimethanil and Thiabendazol. There are also fungistatics whose use is approved practically throughout the world, potassium sorbate and sodium bicarbonate. As all are chemical products, the former, also being known as conventional fungicides, they do not enjoy good press. Are the residues of these chemicals a problem for the health of consumers? According to the EFSA (European Food Safety Agency) the answer is clear and resounding; as long as its residue remains within the so-called Maximum Residue Limits (MRL), their ingestion is a long way from causing any problem.
We are probably facing a question of perception on the part of consumers and society in general; the campaigns of NGOs such as Greenpeace have been successful and the extensive tests carried out, leading the European agency EFSA to consider them safe, have not been placed on the other side of the scale to provide a balance, furthermore there is the reduction of post-harvest losses that is achieved with the correct use of conventional fungicides. In the same vein, the mitigation of losses and reduction in waste are probably much more relevant to the sustainability of the planet than any negative environmental effect that the use of these fungicides may have. Post-harvest losses in fruit and vegetables are around 5-20% in developed countries and 15-40%, according to different sources, amongst them the FAO. Although their decay is only one of the reasons for these losses, it is the most relevant. For example, within our sector it is well known that only a few years ago there were many containers shipping lemons that arrived in Cartagena with decay percentages in excess of 40% and that they had to be discarded in their entirety. With fungicides, industrial efficiencies in controlling decay of close to 100% can be achieved, while, although much research has been done in various physical and biological methods of “green chemistry”, similar efficacies have never been reached and it is for this reason that conventional fungicides are still widely used.
At Citrosol we have been working for many years on organic and greener solutions for arresting decay, but it will be difficult to reach efficacy with sporulation control as high as those we achieved with Imazalil. Maybe a reader will be wondering why their results in decay control are not so brilliant. There may be several answers, but the most common is that resistance to Imazalil has developed. Strains of Penicillium digitatum and P. italicum have evolved to become resistant to the fungicide. Resistance to fungicides is like a hidden enemy there to thwart produce arriving in good condition. The development of resistance is a process that slowly but surely decreases the effectiveness of fungicides. Without monitoring programs to evaluate the evolution of the spore populations of resistant P. digitatum and P. italicum, the detection of the problem is not noted until the first complaints about decay at destination arrive. At Citrosol we have been working for years on resistance monitoring and on treatment and sanitation programs for its management. One of the advantages that organic or “green chemistry” methods and products could have is that as there are several different mechanisms of action to these products, it is much more difficult for resistance to them to appear. However, at the moment there are no mixtures, or cocktails, of treatments based on organic products (certified inputs for organic farming according to EU regulations), and/or biological, physical or “green chemistry” that exceed the efficacies that can be achieve with fungicides as long as the spore population is not resistant to them. As the renewal by EFSA and the European Commission of the active materials that are currently in this process, Imazalil and OPP, is on the right track, it is expected that in the near future the aforementioned products will be allowed to continue contributing to decay control and thus to the mitigation of losses and reduction in food waste in fruit and vegetable produce.
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