Three neonicotinoids - thiamethoxam, clothianidin and imidacloprid - have been banned in the EU after they were implicated in the collapse of honey bee populations. But the NFU is asking for an emergency authorization to deal with cabbage stem flea beetle on rape crops.
In May Defra rejected a plea from the NFU to use neonicotinoids on rape, saying there was insufficient evidence that it would be beneficial.
The NFU has now made changes to its application to answer questions from the Expert Committee on Pesticides and demonstrate to Defra that the application is limited and controlled. It also looks again at AHDB data showing cabbage stem flea beetle pressure across the country. The committee will assess the request on 14 June.
NFU vice president Guy Smith said: "I cannot overstate how vital neonicotinoid seed treatments are for protecting crops facing pressure from cabbage stem flea beetle.
"I am quite convinced that if next autumn we have a difficult establishment window for oilseed rape then many farmers are going to lose their crops without neonicotinoids.
"Evidence from research institutions such as Rothamsted clearly shows we have an increasing pyrethroid resistance problem in pests and this is well-evidenced with cabbage stem flea beetle. Farmers cannot control the pest in areas with high resistance without these critical seed treatments. Continued resistance to pyrethroids just isn't sustainable for farm businesses."
Friends of the Earth, a key opponent of nicotinoids, has urged the Government to refuse the application.
Head of campaigns Andrew Pendleton said it would be "doubly reckless" to allow emergency use, having turned a request down last month.
"Oilseed rape yields have actually risen since the ban on neonicotinoid pesticides was introduced, while the evidence of the harm these chemicals pose to bees has increased.
"Bees are essential for pollinating our crops - we can’t afford to gamble with their future. The Expert Committee and the government must uphold the ban and keep these dangerous pesticides out of our fields."
The group added that damage from slugs was as much of a problem in 2015 as cabbage stem flea beetle, but neonicotinoids could be counter-productive to slug control by damaging the insects that eat slugs.