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Cabbage Stem Flea Beetle Control

A few days ago, after seeing a post on twitter about flea beetle, one of my colleagues gave me this interesting topic to mull over...   After a little bit of sleuthing around the subject, I discovered that if I so desired, I could probably set any agricultural chat site alight with the words ‘cabbage stem flea beetle’ alone.  So clearly this topic has suddenly become quite combustible this Autumn – but why, I hear you ask.

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Current Search Trends On Google around flea beetle damage in OSR.

 

The Cabbage Stem Flea Beetle (widespread in both Europe and the UK) typically migrate into oilseed rape crops during crop emergence, at the crops most vulnerable stage, which takes place around this time of year. In severe cases of damage, the beetles can destroy the seedling before it has even emerged.  Equally as damaging is ‘shot-holing’, when the beetles pummel the early leaves, leaving the plant’s growth seriously stunted.  This year, in some cases, damage has caused growers in the Eastern soils to write off entire fields, in places where damage had previously never been serious enough to warrant treatment.

The crux of the matter is that the flea beetles life-cycle is temperature-driven, and since air temperatures above 16 degrees are more favourable for CSFB migration, the warm July and August have caused flea beetle numbers to soar, with sobering oilseed rape crop losses.  Some are choosing to re-drill, while other farmers are writing off their entire planted area of oilseed rape, citing that the beetles have not left one plant undamaged.

The EU ban on the use of neonicotinoid seed dressing means that oilseed rape farmers battling the beetles have their hands tied, and essentially have nothing remaining in their armoury save pyrethroids and broad-spectrum insecticide.  While the ban on neonics had the principal protection of bees and pollinators in mind, back in 2013, according to Forbes, DEFRA argued that there was not substantial evidence that bee populations were being drastically reduced as a result of neonicotinoids. Even members of the British Beekeeping Association were quick to note that justification for the ban was partial.

The irony of it all is that you only need to speak to a few farmers on the ground, who will tell you that the losses they are making on oilseed rape make it unsustainable to continue growing.  As a result, the flowering crop that pollinators rely on for their spring feed will be decimated, and that certainly sounds more plausibly bee-harming.  I do not intend to scoff at the argument of the environmentalists.  I seek only to point out that the broad spectrum-insecticide sprays and foliar applications that are used in place of neonics needlessly kill greater numbers of insects. There is a genuine feeling that the imposed restrictions will do nothing measurable to improve bee health and pollinator populations.  So, in conclusion – what really is better for the environment – neonics or broader and more frequent use of insecticide?

Besides anything else, it prevents British Farmers from competing on a level playing field with their international peers.  Many are simply aborting oilseed rape as a growing option, and a recent study by the HFFA marked a 912,000 ton drop in oilseed rape production across the EU.  The end result will be, of course, that we end up importing our oilseed rape from countries such as Australia, the Americas and the Ukraine, where neonicotinoids banned in the UK are widely used.   So, at the end of play, we import large amounts of oilseed rape (environmentalists – your food miles alarm bells should be ringing) which has been grown in a country that utilizes full, supposedly harmful, neonic controls – do you still think banning neonic controls in the UK is a worthy scheme? I side with the NFU Deputy President, who is quoted as saying in a recent FWI online article “It’s the economics of the mad-house.”

With farmers neonic powers regrettably removed, there is a question of what farmers combatting flea beetle are advised to use instead.  Essentially, they fall back on outdated and ineffective pyrethroids, because they have no other choice.  If flea beetle damage is identified in your fields, it is advised that you treat it with a full dose of insecticide from the first attack.  However, pyrethroids should only be applied when necessary, as it is widely accepted that many of the pests that we seek to target are resistant to almost every weapon left in our armoury.  What’s more, an increase in frequency and extent of spraying will only speed up resistance further.

Is there anything that can be done? As the odds have sized up against oilseed rape growers this Autumn, I predict that following crop losses, many farmers will not embark on the risk of growing oilseed rape again.  However, having carefully assessed what has and hasn’t worked for over the past few seasons, we have put together a few recommendations for oilseed rape growers in the future.

  • entomologists would suggest spraying Flea-Beetle damaged oilseed rape at night, as this is when the beetles are most active.
  • Early drilling is recommended for early crop establishment, before the beetles migrate in
  • Thinking ahead, fields at closest proximity to previously oilseed rape fields are high-risk areas
  • Damage should be treated at the first sign of an attack, with full dosage (this best tackles pyrethroid resistance issues)
  • Some bodies suggest companion cropping, where white mustard is grown as a sacrificial crop near oilseed rape, to reduce grazing damage by adult beetles. It is thought that the white mustard (being also a brassica like oilseed rape) would lure the beetles away from feeding on the oilseed rape.
  • Spreading pig slurry before cultivation has also been found beneficial

Obviously, it is clear that this year has been exceptional in terms of the weather and other factors combining to make it unprecedentedly difficult to grow Oilseed Rape.  However, in my research, what strikes you is that the farming industry hold the Neonic Ban largely responsible, for the increasing difficulty faced by oilseed rape growers.

 

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