Recent reports have suggested that more than a tenth of fruit and vegetables may contain excessive and illegal levels of pesticides. No further information about the type of pesticides or the active ingredients has been reported at this stage. However, data from the National Statistics Office suggests that fungicides are the most frequently used group of pesticides, followed by herbicides and insecticides.
The occurrence of high pesticide levels in food has been associated with calls for improved data collection and for severe penalties when maximum residue levels are exceeded. This is understandable, given that pesticides have been linked to a wide range of health hazards and environmental impacts.
Unfortunately, the debate stirred up by the latest report on pesticide use was not accompanied by a discussion of ways in which we may reduce dependence on this group of chemicals. The term ‘sustainable intensification’ is increasingly being used to describe the use of technologies that can result in the production of more food from the same area while reducing negative externalities. Over the past years, I have been involved in research relating to the sustainable intensification of agriculture and would like to share this experience because of the relevance to the discussion.
Many will remember the recent invasion of the tomato leafminer (Tuta absoluta). This pest feeds on most of the tomato crop, leading to substantial losses in crop yield. It is also known that chemical applications are often not particularly effective against the tomato leafminer. Past research has shown that biological control, that is, the use of other ‘beneficial’ insects to predate on and control the populations of the pest, can result in lower infestation levels and less crop damage.
In a study conducted in a greenhouse environment, we have shown that, by providing specific plant resources, we could increase the survivorship of a parasitoid feeding on the tomato leafminer by up to six times, while in other studies, we show that field populations of these beneficial insects can be increased naturally, thereby increasing pest control effectiveness.
The advantage of these techniques is that, through the enhancement of the local environment, populations of these beneficial insects can build up to control the pest. Insect pests may be controlled by other insects that colonise and establish in field environments by natural means, thereby increasing the resilience of the agricultural systems.
This also contrasts with the traditional biocontrol in which predators or parasitoids are bought, and often imported, to control a pest. While this can often be done, the risks associated with the introduction of new genes and species should be evaluated.
The maintenance of agricultural biodiversity in field environments may also lead to other benefits, for example through improved crop pollination. Some crops require insect pollination for an enhanced crop yield, while in others, this is essential for crop production.
A few years ago, we valued the contribution of pollinators for fruit and vegetable production in Malta at around €8 million per year, representing approximately 15 per cent of the Maltese agricultural production that was used for human consumption.
Others have found that animal pollinated strawberries are heavier, have fewer malformations, reach higher commercial values and have an extended shelf life or that open pollinated apples are larger and contain more sugar than those in which pollinators are excluded.
Many farmers already supplement natural populations of pollinators through the use of domesticated species. But studies have shown that the maintenance of wild flowers for pollinators in agricultural landscapes is important for ensuring the conservation of this group, with substantial evidence demonstrating that this can lead to an improved crop pollination and production.
These observations illustrate how, through minimal investment in our agricultural environment, we can improve the resilience of agricultural systems for pest management and crop production.
Mario Balzan has for several years been involved in research on sustainability in agriculture.