Pesticide Dilemma

First Published: C&I Issue 1, 2021

Cath O’Driscoll | Read Time: 9 mins

With a growing population to feed, the world needs pesticides more than ever. But we also need to reduce reliance on them to better protect our increasingly damaged natural environment. Cath O’Driscoll reports from the 2020 virtual British Crop Production Council Congress

Pesticides continue to be vital in securing global food supply. Yet they can also have severe negative impacts on the environment. And with a global population projected to hit nearly 10bn by 2050, we will almost certainly need to use more of them.

Around the globe, farmers will need to produce vastly greater quantities of food with little if any extra available land area. In the UK, for example, Prime Minister Boris Johnson recently pledged to protect 30% of UK land by 2030 to support ‘the recovery of nature’. Since much of this land is already protected, in practice this equates to a further 4% – around 400,000ha – that will be unavailable for agriculture.

A changing climate – including successive warmer winters in recent years – has also brought new pests and diseases to be tackled. ‘Mild winters have tended to increase the use of herbicides because we don’t have winter any more to kill off the weeds,’ said Per Kudsk, professor of agroecology at Aarhus University, referring to the situation in Denmark. ‘Spraying [in] autumn and spring is quite common now.’

Tighter environmental standards, meanwhile, have slashed the armoury of pesticides available to farmers to a fraction of the number available ten years ago. ‘At least 50% of insecticidal active substances have been withdrawn or revoked in the last ten years [2008-2018] from 56 down to 26,’ said DEFRA’s Susie Willows. This in turn has exacerbated problems of resistance, with many crop pests and diseases becoming increasingly resistant to the few remaining plant protection chemicals.

Alarmingly, few new agrochemicals are under development, as Willows also pointed out: ‘In the last ten years we’ve only had only one new insecticidal chemical group.’

And while much hope has been pinned on nature’s own biopesticides, to date these have been mainly used in the horticulture and soft fruits industry.

In Europe, meanwhile, public fears over the safety of genetically modified food crops is another barrier to developing more robust varieties inherently better able to resist pests and disease – which could otherwise play a major role in reducing pesticide use.

Precision application

A slew of technologies to improve pesticide targeting are already deployed or under development, according to Sagentia’s Alun James, speaking at BCPC. ‘To me it’s all about precision and how to identify what to spray and where.’

He pointed to a few notable examples.

Precision Decisions’ variable rate control boom deploys chemistry at different rates depending on the speed of the tractor and its course. The flow rate is varied at different sections of the boom and is accurate to a few metres, reducing areas of crops receiving a double dose, for example.

ExactApply from John Deere consists of an array of selectable nozzles that allow tractor turning compensation and individual nozzle control. Smart diagnostics are used to improve, monitor and document sprayer applications at the nozzle.

Blue River’s See & Spray technology uses computer vision and machine learning in conjunction with controlled spray nozzles to target application down to 5cm. The company claims that this can reduce agrochemical use by up to 90%. In 2017, John Deere acquired Blue River for $305m.

Further from deployment, Syngenta, G’s and academic partners Harper Adams University and the University of Manchester cooperated on a hyperweeding project from 2014-17. The project, funded by Innovate UK, aimed to selectively identify and irradiate weeds within a crop using hyperspectral imaging, destructive tracking lasers and precision spraying. The method was trialled in a Cambridgeshire lettuce field and demonstrated the potential to control weeds in vegetable crops with highly precise, ultra-low volume applications of non-selective herbicide.

Salisbury, UK based Small Robot Company, meanwhile, is trialling the use of lightweight robots for crop and soil monitoring, precision feeding and weeding, and precision drilling and planting. Tom is a crop monitoring and mapping robot that can collect per plant level data on 20ha/day. Dick is an autonomous non-chemical weeding robot and Wilma is the AI interface between Tom, Dick and the farmer.

Trial partners include the National Trust at Wimpole Hall and Waitrose in Hampshire.

The idea is that the robots are deployed on a service basis, enabling farmers to be more efficient, precise and productive, and kinder to soil and the environment, according to the company.

So what can be done to reduce pesticide use, while at the same time increasing food productivity? While no hard figures are available, what is clear is that more pesticides are sprayed than are actually needed. For example, due to pesticide ‘drift’ or by spraying unaffected crops.

Determining when and where a pesticide is necessary is yet another thorny issue. Maximum threshold values involve sampling and testing plants and/or soil for the presence of pests and diseases at various times throughout the growing season. However, they are notoriously labour and time intensive and prone to error.

A pesticide tax has long been on the table for discussion in many countries and appears to have achieved results in Denmark (see Box). However, this idea has not been adopted in the UK. Instead, users of professional pesticides – including farmers – subscribe to a voluntary initiative to consider the principles of Integrated Pest Management (IPM) before pesticide use. ‘IPM is a holistic approach to pest management that is both economically and ecologically sustainable,’ said Henry Creissen from Scotland’s Rural College.

A 2018 survey led by Creissen revealed that all farmers in England, Scotland, Ireland and Northern Ireland had adopted IPM to some extent (Pest Management Sci, doi: 10.1002/ps.5428). However, as measured by a new universal metric for quantifying adoption of IPM in temperate arable farming, only 15 of 225 farmers (6.7%) had adopted more than 85% of what is theoretically possible.

Sustainable protection

In October 2020, SCI hosted a webinar entitled Feeding the future: Can we protect crops sustainably? One of the big challenges is the available land area for growing crops, noted Keith Norman, an independent agritech consultant: Currently, 11% (1.5bn ha) of the globe’s land surface (13.4bn ha) is used in crop production – both arable land and land under permanent crops.

Precision agriculture could identify where yields could be increased, allowing less productive land to be placed into environmental stewardship schemes, Norman said. Aerial mapping can also be used to plan seed rates used across a field, resulting in a more uniform and productive crop.

Rapid methods for the early detection of crop problems are also urgently needed. Neil Boonham of Newcastle University, for example, highlighted advances such as lateral flow devices for quick in-field detection of resistance in black grass, and the use of next generation genetic sequencing platforms to flag up ‘multiple problems in whole populations’.

The SCI webinar was organised by the SCI Agrisciences, Food and Horticulture groups, the Institute for Agri-Food Research and Innovation (IAFRA), and Crop Health & Protection (CHAP). For further information, see a summary on the CHAP website:

There were differences in practices between farmers and the regions – for example, crop rotation and minimum till were more common in England. ‘High adopters of IPM are more likely to cite an independent agronomist [not linked to commission for pesticide sales] as one of their top sources of advice,’ said Creissen.

There is a strong environmental and political case to minimise use of chemicals on farmland in spite of increasing herbicide tolerance in weeds. Knowing where to spray, when to spray and what to spray becomes increasingly important.
Alun James Chief Technology Officer at Cambridge-based Sagentia

Some of the core elements of the Sustainable Farming Incentive (SFI) component of the Environmental Land Management scheme will be launched in 2022. This will pay participants for delivering some of the foundational elements of environmentally sustainable farming; this is likely to include some IPM actions, according to Willows.

Following the BCPC Congress, in late November 2020, the UK government published a roadmap outlining changes that will come into force over the next seven years to help farmers adapt and plan for the future. The plans are centred on support that rewards farmers and land managers for sustainable farming practices. A key feature of the roadmap is that it will use the principles of the government’s Environmental Land Management Scheme to incentivise sustainable farming practices – including pesticide reduction, creating habitats for nature recovery and establishing new woodland to help tackle climate change. The changes will only apply in England. Devolved administrations in Wales, Scotland and Northern Ireland will draw up their own plans.

‘There is a strong environmental and political case to minimise use of chemicals on farmland in spite of increasing herbicide tolerance in weeds,’ said Alun James, Chief Technology Officer at Cambridgebased Sagentia. ‘Knowing where to spray, when to spray and what to spray becomes increasingly important. We’re starting to see a migration from whole field broadcast spraying to zonal spraying and in future it could be down to the per plant level.’

James – who prefers the term precision application – explained some of the barriers. ‘The target is going to be a 90% reduction in the amount of chemistry applied to a field. The equipment required to deliver the capability to target the right chemistry at the right plant is expensive and complex, with significant development costs. Although there is strong regulatory and political drive to reduce the use of chemistry on our farms, the development costs of these new technologies are a significant barrier to entry and unfortunately there is currently little incentive for either agchem companies or equipment manufacturers to invest in better targeted technologies.’

And he also questioned how precision agriculture would be regulated. ‘Is it per field or on an acreage level or do you now need per plant level?’

Ultimately, what is needed, James said, is a change of business model where third-party companies provide such technologies to farmers as a service. Instead of buying litres of herbicide, for example, they might buy a weed-free hectare, he pointed out. ‘The farmer will pay for results not the inputs.’

Sensors and satellites and robots – and greater sharing of protected in-field data – are other areas under development that could dramatically improve targeting, according to BCPC attendees. They also called for the industry to develop more chemical and pesticide additives, along with better designed spray nozzles, to reduce pesticide drift.

Danish experience

‘Reducing pesticide use [in Denmark] has been on the political agenda long before the Sustainable Use Initiative (SUI) was invented in the EU,’ said Per Kudsk of Aarhus University, speaking at BCPC. The country set out its first pesticide action plan in 1987, he pointed out.

Various approaches were introduced, including a Treatment Frequency Index (TFI) that reflected the intensity of pesticide use and a VAT-based approach where pesticides were taxed based on sales.

In 2013, however, the system was changed to reflect calls for a reduction of pesticide impact rather than pesticide use. The tax system was revised to reflect this change and the uploading of spray records per crop became compulsory. Instead of TFI, regulators were more interested in Pesticide Load [PL] based on the known hazards, the formulation and the intrinsic properties of the active substance. The PL indicator focused on three categories – human health, pesticide fate in the environment and ecotoxicology. Using these sub-indicators, the pesticide load could be evaluated for a range of plant protection products.

Whereas Danish farmers were routinely exceeding targets based on TFI, they have been meeting those for pesticide use based on PL, said Kudsk. ‘We have had a stable or decreasing PL at the same time as we have had an increasing TFI, which clearly shows that even though the farmers have been using more pesticides, they have shifted to more benign pesticides with a lower PL.’

But while this is good news in the short term, there could be difficulties with this approach in future, he warned.

‘The risk is that this tremendous difference in tax will promote the use of specific products – the ones with the low taxes. One of the drawbacks of this [PLbased] tax system is that you may get less diverse use of pesticides.’

This in turn could accelerate the evolution of resistance.

Kudsk is a firm believer in the power of providing targeted IPM advice to farmers. ‘The role of advisory services has always been considered pivotal in Denmark in promoting the uptake of IPM,’ he said.

Crop spraying. Pesticides being applied to crops in a field by a crop sprayer. This crop sprayer is being operated by George Roworth, a finalist in the Farm Sprayer Operator of the Year 2009 competition. This competition judges entrants on their safe and efficient use of crop protection products to increase crop yield, while still meeting standards for public, operator and environmental safety.

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