Overcoming insecticide resistance

Developing new crop protection products is difficult and costly so it remains vital to protect effective products from the development of resistance, even against a backdrop of the fact that 'toolbox' of usable products is dwindling year on year.

To assist in making the most of what we have, Pangaea Biosciences has added an effective new tool in the form of Booster, a new optimised and patented primer formulation which, when used with insecticides, can help overcome resistance.

“In the UK, we are all familiar with weed resistance as it is a widespread problem, but globally insecticide resistance is more problematic,” said John Edmonds, global product development and regulatory manager for the company.

The IRAG [international regulatory body] defines resistance as the 'inheritable change in the sensitivity of a pest population that is reflected in the repeated failure of a product to achieve the expected level of control when used according to the label recommendation for that pest'.

In Europe, there is significant resistance in pollen beetle (meligethes aeneus) to pyrethroids. This has been the case since 1999 when it was first identified. And across Europe insecticide resistance resulted in a 21% yield loss of rapeseed and in some cases a 70% loss.

More than 60% of pollen beetles are resistant to pyrethroids and in some countries, such as Poland, the Baltics, the Czech Republic and Lithuania, it is much higher than that. Pollen beetle is a major threat to the profitability of oilseed rape the further East you go in Europe.

The Czech Republic was the first country to launch Booster – there more than 200,00 ha of rape suffers from resistant pollen beetle. Booster enjoyed remarkable success in its launch year, achieving a 20% market share, with 40,000 ha treated, with few issues or problems.

The product is said to restore efficacy to pyrethroids, such as cypermethrin, alpha cypermethrin and lambda-cyalothrin, and in one set of trials the untreated had eight beetles per plant, a treatment of Fastac (alpha-cypermethrin) had seven beetles per plant – showing little activity – but add in Booster and the level of infestation reduced to one beetle per plant.

In German trials in 2022 its addition improved the activity of lambda-cyalothrin by 49% with the insecticide alone giving 36% control of pollen beetle and with Booster 85% control. With cypermethrin, the additional effect was 27% – lifting control of cypermethrin from 58% to 85%.

It works by acting on the cytochrome P450 pathway and so makes the pollen beetle more sensitive to the pyrethroid once again. And it is used to inhibit or neutralise the pest’s defensive enzyme before the pesticide is applied.

The primer leaves the pest in a hypersensitive state so that the concentration of the pesticide will kill even the most resistant types. It does this by deactivating the metabolic pathway (cytochrome P450) in insects, which causes breakdown of an insecticide.

Dr Alan Dewar, who has more than 40 years of agricultural entomological experience, worked with Booster and pyrethroid insecticides in spring rape and reported on its ability. “The persistence of the effect does not last long – around six days – but this is long enough for the crop to produce a viable yield," he reported.

"There was a substantial effect of the treatment plus Booster on the duration of flowering within the plots and the subsequent development of seed pods. This is likely to have had a significant effect on yield at harvest.”

Pollen beetle control is the first registration for Booster in the UK, Czech Republic, Poland, the Baltics, Romania, and Denmark.

Pangaea is also investigating its use with pyrethroids to control cabbage stem flea beetle in winter oilseed rape. This is a major problem in the UK, with resistance to pyrethroids was detected in 2014.

Dr Dewar added: “Ever since the banning of neonicotinoids seed treatments in 2013 in the UK, growers have relied on pyrethroids for the control of CSFB and its excessive use has led to widespread resistance. One reaction is that growers have widened their rotations growing winter rape to one in five or six years which will reduce this pest pressure.

"The impact of cabbage stem flea beetle has changed the growing pattern of rape in certain areas suffering high pest pressure moving away from growing autumn rape,” said Dr Dewar.

Mr Edmonds pointed out that Pangaea had contracted out four replicated trials to Eurofins on the control of cabbage stem flea beetle in the UK this year. Interim results from one of the four trials looks as if the use of Booster with pyrethroids did help suppress levels of this damaging pest.

The untreated plot had 13 flea beetle larvae. A plot treated with lambda-cyalothrin had 7.75 larvae and lambda-cyalothrin plus Booster had 4.5 larvae, which looked promising. "One of the difficult issues is that the spray needs to catch the pests that are mostly active in the morning and evening. We need more work before we are confident about a recommendation,” he added.