Government ministers have failed to grasp the seriousness of challenges posed by the withdrawal of important pesticides, scientists and farm leaders have warned.
More research in alternative crop protection is needed to meet demand for food as pesticides are taken off the market due to European legislation, DEFRA has been told.
The warning is contained in an open letter to farm minister David Heath from processor Toby Bruce, of the Association of Applied Biologists, and NFU president Peter Kendall.
"Farmers need to be supported by more practical R&D that will provide them with workable alternative crop protection techniques," the letter says.
Farmers use pesticides as the mainstay of their crop protection because they provide a straightforward and effective way of reducing losses to pests, weeds and diseases, it adds.
"Reducing the availability of certain pesticides before alternative crop protection methods have been implemented would mean an increase in the use of the remaining pesticides."
The warning comes after what Professor Bruce and Mr Kendall describe as "the worst year on record" for fusarium and septoria diseases in the UK.
Growers have also battled blackgrass problems, says the letter, and it is likely that the UK will become a net importer of wheat for the first time in 10 years.
Reducing yield and quality losses is needed to ensure food security, the letter continues, but DEFRA has been reducing R&D on alternatives to pesticides since 2005.
DEFRA has developed a draft national plan aimed at meeting European requirements to reduce the risks and impacts of pesticide use on human health and the environment.
But the letter says the draft plan is "not well connected to the food security context, and as such would appear to be out of touch with the seriousness of the problems" facing agriculture.
"In the context of increasing global demand for food and current concern about food security, there are serious consequences of leaving EU agriculture vulnerable to pests, diseases and weeds."
DEFRA is expected to make an announcement on its full action plan early this year.
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