Pete Jorgensen

Mankind has attempted to increase harvestable yields from food crops by reducing pest damage for at least 4500 years (Coll & Wajnberg, 2017). This battle continues, with the current global spend on pesticides reaching almost $59 billion (Business Wire, 2016). Despite this expenditure, it is estimated that we continue to lose between 20% and 40% of global food production to pest damage (Savary et al., 2012).

Rachel Carson’s book ‘Silent Spring’, published over 50 years ago, delivered a stark warning about the harmful effects of pesticide use (Carson, 1962). There is now a substantial body of evidence connecting pesticides with a wide range of detrimental effects both to human health and the environment (appendices 2 & 3). Examples include carbamates and organophosphates causing neurotoxicity (Costa et al., 2008), and combinations of substances causing over 40% biodiversity loss in freshwater invertebrates (Beketov et al., 2013). Synergistic combinations of substances are rarely studied but can significantly exacerbate toxic effects (Rizzati et al., 2016; Parrón et al., 2014).

Pest resistance is also a serious concern; treatments are becoming increasingly ineffective (appendix 4). There are at least 404 known plant species that have developed herbicide resistance (Heap, 2014) and 553 species of arthropod now resistant to insecticides (Whalon et al., 2008).

As evidence continues to accumulate showing that reliance on pesticides is not sensible, pressures on industry to change its practices are growing. In 2017, the EU rejected relicensing glyphosate for 10 years (EC, 2017) but agreed a shorter 5-year term (Tani, 2017); this has since been extended again. The UK is currently poised to support a complete ban on neonicotinoids (Harrabin, 2017).

Encouraging pesticide reduction in IPM

‘Integrated Management’ (IM) as a methodology for pest control using both chemical and biological controls was first proposed in 1959 (Stern et al., 1959). Modern IPM developed over ensuing decades and should involve a wide range of holistic methods, but critics suggest that there is still too much focus on pesticide use (Cowan & Gunby, 1996; Hokkanen, 2015). The EU has identified the need to recognize the wider costs of this over-reliance on pesticides and deployment must now be both economically and ecologically justified (Council Directive 2009/128/EC). However, many growers remain reluctant to adopt more progressive IPM techniques (Hokkanen, 2015; Buurma & Van Der Velden, 2017).

Barriers appear to be financial: new systems can require high outlays, be complicated and expensive to manage, and carry higher labour costs (McCarthy & Schurmann, 2014). Producers do not feel able to raise their prices to pay for these changes as they risk losing their markets (Buurma & Van Der Velden, 2017; McCarthy & Schurmann, 2014). Some growers who have engaged with new IPM programs have been disappointed when their expectation for increased economic returns are not fulfilled (Buurma & Van Der Velden, 2017).

In Britain, the Voluntary Initiative (VI) is an industry-led scheme engaged in encouraging ‘responsible pesticide use’ (The Voluntary Initiative 1, 2017). A VI scheme set up in 2014 (NFU, 2014) encourages producers to adopt IPM programs and 16 820 producers are using it (The Voluntary Initiative 2, 2017). The same report is devoid of any mention of actual levels of pesticide use. The National Farmer’s Union, an industry pressure group, claims that crop production has been falling in the UK as the result of a reduction in pesticide availability (NFU, 2014). Their report limits the scope of the data used to just five crops. Using much broader data from 34 crops (see appendix 5) it can be shown that total crop production in the UK between 2001-2014 has increased by over 7 million tonnes (18%) while pesticide use has decreased by 14 590 tonnes (44%). The European Public Health Alliance states that there is no basis in fact for expecting industry self-regulation to work in delivering policies that benefit public health (EPHA, 2016). A study by Short & Toffel (2010) concurs with the EPHA and concludes that legislation is a more effective in safeguarding public health (Short & Toffel, 2010). Examples of both failures and successes in industry self-regulation are offered in a more concessionary review by the OECD (2015). In this instance, the NFU (members of the VI steering group) firmly attribute reduced pesticide use in the UK to legislative changes driven by the EU rather than as the result of industry self-regulation (NFU, 2014).

EU law imposes legal limits on the levels of pesticide residue allowed in food (Council Regulation EC 396/2005) and in 2009 member states were directed to legislate on the sustainable use of pesticides (Directive 2009/128/EC). This prompted the UK Parliament to pass The Plant Protection Products (Sustainable Use) Regulations 2012. However, this legislation is tied to the European Communities Act (1972) which will be repealed as part of the Brexit process (Great Repeal Bill, 2017). It would not seem sensible for any government to seek to erase or debase laws aimed at protecting public health and the environment. Even when legislation is in place, it has been shown that a significant minority of producers do not comply with it. A study of 75 samples of leafy vegetable food crops produced within the EU found that 84% contained detectable pesticide residues with 18 (almost 25%) exceeding legally imposed limits (González-Rodríguez et al., 2008). It is not clear whether these breaches occurred deliberately or through ignorance.

The PURE scheme financed by the European Commission recently published a special edition of the journal ‘Crop Protection’ to address ongoing challenges and knowledge gaps preventing IPM implementation (Lamichhane, 2017). The length and complexity of this 157-page publication demonstrates the breadth and depth of expertise truly holistic IPM requires. A daunting prospect for producers with tight fiscal margins operating within an economic system focussed on short-term results.

Alternatives to synthetic pesticides: some limiting factors

There are numerous options in the IPM tool box, but many have complexities or concerns that may leave producers reluctant or unable to use them. One example is biopesticides which are separated into three main groups by DEFRA in the UK: semiochemicals (SCs), microorganisms and natural chemicals (DEFRA, 2012).

SCs are signalling compounds such as pheromones which influence the behaviour or development of an organism (Jorgensen, 2008). Use of species-specific SC lures to trap pests can be an economically viable means of avoiding or reducing the need to use traditional pesticides (Sampson & Kirk, 2013; Weintraub et al., 2017). Many plants produce SCs naturally and companion planting has been used effectively in pest control as part of push-pull systems (Cook et al., 2007). Deployment requires in-depth scientific knowledge about the metabolic processes and life cycles of pest organisms; such knowledge may not be available for many pest organisms and there is a lag between the emergence of knowledge and the production of workable management practices and commercially available products.

Microorganisms such as bacteria and fungi (including endophytes) are effective against a range of pests, and some are commercially available (Glare et al., 2012). Regulatory authorities have streamlined licensing for such products, but in general, they are still more expensive, target specific, and have a short shelf life (Kumar, 2012).

Natural chemicals or botanical insecticides (BIs) are chemicals produced within plants that exhibit pesticidal properties (Miresmailli & Isman, 2014). They are considered safe, biodegrade quickly and have fewer detrimental effects on beneficial predators (Pavela, 2016). It is estimated to cost around €300 000 to produce a single plant protection compound that is market ready (AHDB, 2015). Between 2006 and 2012 the UK government spent a total of £2.1 million on research into biopesticides excluding semiochemicals (DEFRA, 2012). This level of investment is unlikely to have much impact. Agricultural chemical companies will be seeking alternatives to replace the increasing number of products being phased out but difficulties claiming intellectual property rights for BIs may dissuade them. Some BIs may also be associated with undesirable consequences similar to synthetic pesticides. For example, the biopesticides Abamectin, Azadirachtin, Spinosad and even citrus oil were found to have detrimental effects on the non-target beneficial predator Orius laevigatus (Biondi et al., 2012). Fast tracking approval for these substances (Real IPM, 2017) may be unwise.

The EPA in the US differs from DEFRA in their classification of biopesticides: biochemical pesticides, microbial pesticides and plant-incorporated-protectants (PIPs) (US EPA, 2017). The key difference is the inclusion of PIPs which are produced by genetically modified (GM) organisms.

Bt corn creates insecticidal chemicals within its own organs, reducing or eliminating the need to apply external treatments (Hayley, 2012; Jones, 2010). This has led to a dramatic decrease in the use of externally applied insecticides to control pests such as the corn borer (Malakof & Stokstad, 2013). Insects are developing resistance to Bt maize crops (Tabashnik et al., 2013). Non-GM havens within fields are used to maintain a non-resistant insect population which dilutes the gene pool. So far, this has been effective in containing the problem (Ibid.). These additional management techniques add to the cost of incorporating GM technology and the threat of pests developing problematic resistance cannot be ignored.

The use of HT (herbicide tolerant) crops has led to massive increases in the application of glyphosate – up to 300% more on some crops such as cotton (Riley et al., 2011). Increased use of HT GM crops may have led to the development of increased herbicide resistance in crop pests (Tabashnik et al., 2013). Increasing amounts of herbicide may then be required to kill resistant pests (Perry et al., 2016). This is a vicious cycle with an undesirable outcome.

In addition to biopesticides, natural enemies can be deployed as a biological pest control (Huffaker, 1976). Natural population management strategies can be used but require a thorough understanding of inter-organism ecology and can only be used in open systems (Messelink et al., 2012). Organisms such as nematodes and parasitic wasps are commercially available but have limitations such as high expense, short shelf-life, target specificity and are only be effective in certain conditions (Lazarovits et al., 2014).

Is organic the answer?

Organic production uses less damaging, holistic IPM systems, and may employ some of the alternative pest control methods discussed (Lamine, 2011). Prevailing opinion is that organic methods cannot compete with conventional systems in terms of yield weight: a meta-analysis of 362 published organic v conventional crop production systems suggests that yields using organic methods are on average 80% that of conventional crops (De Ponti et al., 2012). Cultivation techniques, soil type, topography, choice of crops and longevity of study are all factors which can influence outcomes. Long-term studies by The Rodale Institute (The Rodale Institute, 2011), and a UN sponsored review of modern academic sources (De Schutter, 2010) suggest that it is possible to equal and even increase crop productivity levels without reliance on synthetic chemical inputs. Rodale claims that the benefits of organic systems can only be seen over the long term and most other studies are too short for the benefits (such as improved and balanced soil ecology) to become evident.

Organic methods have more economic and ecological longevity, if new methods of measuring the social and ecological impacts of production techniques are accounted for (Pimentel, 2014; Vasileiadis et al., 2017). There is also high demand from the public: the total global organic food market is forecast to grow from $81.6 billion in 2016 to between $320-$456 billion by 2025 (Grand View Research, 2017; Research and Markets, 2017). The UK saw a 7.1% growth in organic food production in 2016 to £2.09 billion - around 25% of which is exported (The Soil Association, 2017). While organic methods are considerably more environmentally friendly, they are not flawless. Concerns include environmental pollution with high levels of nitrogen leaching and nitrous oxide emissions (Tuomisto et al., 2012).

Conclusion

Pesticides facilitated an unprecedented growth in the human population during the 20th century and remain integral to industrialized food production (Cooper & Dobson, 2007; Pingali, 2012). Credible evidence of chronic illness, ecological disturbance, and increasing pest resistance, mean that reliance on synthetic pesticides will be increasingly harmful on the long run.

Organic methods of growing encourage biodiversity and are gaining in scientific credibility. Such practices can be naturally robust but are not absent of environmental concerns, and there is legitimate doubt about whether future food requirements can be fulfilled organically.

Necessity is the mother of invention and the UK has already succeeded in making dramatic reductions in its reliance on pesticides despite protestation from the industry old-guard. Much relevant UK law was brought about directly or indirectly as the result of its EU membership. The legal framework in place following Brexit is uncertain, but pressure to continue reducing pesticide use is unlikely to abate. In the interest of public and environmental health, it is probably desirable to maintain increasingly robust legislation. Government regulation combined with growing public demand forms a push-pull system that can encourage producers to become less dependent on synthetic pesticides. In turn, this could increase demand for less harmful pest management solutions, increasing innovation, and economic viability.