Writing on the farming and environmental consultancy's website, he said: "A key question is the cost of establishing a system for generating, assessing and making decisions. Many pesticide approval holders already think the EU is a small market compared to other potential growth markets for their products. They would need to see the UK as a viable place to develop products for, and the likelihood of that will depend on how close the UK 'rules' were to others' approvals regulation."
Given this, he said: "It is likely that there will be a need for continued relationship with European approvals bodies such as EFSA who independently assess research and evidence to make recommendations on pesticide approvals."
He added: "It is very unlikely that any government would wish a relaxation of standards, especially those that help protect human health and the environment," while home and export markets would also continue to determine crop characteristics such as maximum residue levels.
"The scope for major changes to regulations will be market driven and will therefore be constrained as they will need to ensure they are very close to, or possibly higher than, those of major trading partners," Clarke concluded. "While many may have a demand for significant change, there may be limited scope to alter what can or cannot be done in the UK."
Meanwhile, a recent Global Food Security workshop on pesticide replacement that brought together academics, policymakers, industry and other stakeholders suggested a range of strategies could ultimately lead to pesticide-free growing, according to the programme's strategy and policy officer David O'Gorman.
"A strong theme at the workshop was integrated pest management (IPM) strategies for pest control," he said. "There are, however, issues around the complexity of IPM and the scalability of biopesticides from greenhouses and controlled environments to their usage in fields and large-scale agricultural practice. In large-scale operations, biologicals and IPM are not as reliable as their chemical counterparts, and further engagement is needed with farmers and growers to reap the maximum potential benefits."
He added: "IPM does not lend itself well to commercialisation in terms of intellectual property so there is less incentive for crop-protection companies to invest in this technology."
Workshop attendees agreed that a whole-system perspective is needed, he said. "This is because alternatives to pesticides can have unintended consequences. For example, other methods of weed control, such as ploughing, reduce soil's ability to store carbon, increasing emissions and depleting the biodiversity of micro-organisms."
Recent advances in genome engineering "could offer game-changing potential for agriculture", he added, suggesting that the gene editing tool CRISPR (clustered regularly interspaced short palindromic repeats) "has the potential to edit genomes with unprecedented precision", pointing out that virus-resistant papayas and plums have shown that this and other gene-editing technologies can deliver effective resistance.
"But although the science is unquestionably brilliant, increased public confidence in novel technologies will be needed for wider uptake," added O'Gorman. "Many at the workshop thought that the potential for agri-engineering solutions is (almost) limitless and could drastically reduce the demand for pesticides."