Decis: a classic with innovation potential

“More than 300 crops can be protected from infestation by pest insects using Decis”, according to Wirtz. The product is currently registered in more than a hundred countries. Bayer CropScience calculates that an average of around 30 million hectares is treated with the product each year – that’s about two percent of the global agricultural surface.
All of this makes Decis one of the most popular of all pyrethroid products. Pyrethroids are the class of substances developed by chemists after using the chemical components of pyrethrum powder – i.e. dried and ground chrysanthemum flowers – as a starting point. The researchers managed to achieve an increase in insecticidal efficacy, along with an improvement to the stability of the molecules. Natural pyrethrum is actually light-unstable, so it is unsuitable for use outside in the field, despite its insecticidal potential.
The decisive synthesis work was done by researchers at the Rothamsted Research Institute in England (see also box on page 21). In 1974, they developed deltamethrin, and after the necessary development phase, the resulting product – Decis – entered the market for the first time in May 1979, some 30 years ago.

The start of a revolution
The introduction of pyrethroid compounds such as deltamethrin was tantamount to a revolution in the control of insect pests. Suddenly, application rates of around ten grammes per hectare were sufficient. This was in contrast to the organophosphorus acid esters that were widely used at the time: these had to be applied in amounts of up to 500 grammes per hectare.
One of the factors behind Decis’ particular ability to be effective at extremely low doses was the high degree of purity of deltamethrin, which comprises a single, highly-active isomer. Most other pyrethroids were (and remain) a mixture of different structural variants of a molecule, some of which are active and others not. Deltamethrin proved to be 750 times more effective than natural pyrethrum. The pyrethroids thus provide an excellent example of how scientists have been able to take a naturally-occurring substance as a starting point, modifying it such that the efficacy and other properties of the substance are significantly improved.
A further advantage associated with deltamethrin is the rapidity of its action on the nervous systems of pest insects. And all that against the background of an improved ecotoxicological profile compared with conventional products at the time. The introduction of the pyrethroids represented a true milestone in the story of insecticides. “Only a very few other active substance classes have had such an extensive influence on crop protection”, stated Dr. Rüdiger Scheitza, Member of the Bayer CropScience Board of Executive Directors, on the occasion of a symposium on pyrethroids held in June 2009 at Bayer CropScience’s Headquarters in Monheim, Germany. The fact that the company devoted a major specialist conference to the pyrethroids, 30 years after the introduction of Decis, is an indication of the status this group of substances still enjoys today.
Indeed, in terms of turnover, pyrethroids are still the second-most important group of substances in the insecticides segment of the crop protection market, with a market share of 15 percent. Kai Wirtz is convinced that “almost all farmers will have pyrethroid products in their crop protectant store”.
The original product, Decis 25 EC, has been a reliable, well-proven tool in agriculture for a good 30 years now. But during this time, Bayer CropScience has also continued to develop the product further – bringing new formulations onto the market on a number of occasions. These included products such as Decis EXPERT (with increased concentration), Decis ULTRA (for aerial spray application), the granule formulation Decis PROFI and Decis Protech, which is especially environmentally compatible and free of classification by virtue of the solvent it contains.

Decis fLUXX: “Fluid Intelligence”
At the beginning of 2009, the introduction of Decis fLUXX set another milestone in the deltamethrin success story. This new formulation contains special additives that ensure strongly enhanced efficacy of the active substance at the leaf surface. “Among the advantages is the fact that spray solution run-off from the leaf is inhibited”, comments Kai Wirtz. “Instead, the droplets stick to the leaf in an optimal way, and even become distributed across the entire leaf surface.” And there’s more: the use of a new type of wetting agent prevents the active substance from crystallizing out. “Because the active substance remains in liquid form, the high level of insecticidal activity that would normally only be seen straight after application is maintained, extending until long after the application”, explains Wirtz.
These special attributes led the developers of Decis fLUXX to talk about “Fluid Intelligence” – “clever droplets” if you like. The droplets seem to know how they should behave in order to work most effectively, even to the extent that they reach insects that are hidden. In field trials, the new formulation has proven itself to be a significant further development: it is better than standard treatments both in terms of the speed and the efficacy of action.
Beside the Decis product family, delta¬methrin has also long been proving its worth in combination with other active substances. Proteus® and Confidor® ENERGY are examples of products in which Bayer CropScience has created combinations of deltamethrin with the neonicotinoids thiacloprid or imidacloprid.
“This type of combination will play an increasing role in the future”, is Kai Wirtz’s prediction. The pyrethroid Asset Manager is thinking mainly of the large number of markets that demand low price pesticides. At the moment, these markets are dominated by products from so-called “old chemistry”, that is, by organophosphorus acid esters, organochlorine compounds and carbamates. But many products based on these classes of active substance will disappear from the market sooner or later, so replacements will eventually be needed. “Pyrethroid products are an especially attractive alternative in countries where farmers are dependent on very cheap solutions – for example in the emerging markets of Brazil, China and India”, explains Wirtz. What’s more, the pyrethroids have proven to be particularly strong against the very pests farmers currently prefer to control with “old chemistry” – that is, against butterflies, sucking insects, and beetles.

The Decis tree continues to flourish
Some completely different solutions involving pyrethroids are also thinkable. For example, Bayer CropScience is working to develop pheromone traps that carry sex attractants inside, but have a layer of deltamethrin on the outside. Pest insects drawn by the volatile attractant are thus automatically controlled as soon as they touch the surface of the trap. These pheromone traps are an innovative approach to using a conventional crop protection product to control damaging pests in a way that is as compatible as possible with the environment. In many situations, traps of this type could even make spray applications to fruits or vegetables obsolete.
“In Spain, we’re currently testing the first promising pilot application of this type against fruit flies in citrus and pome fruit plantations”, notes Kai Wirtz.
So Decis’ spiral of innovation continues to turn. “Our current product developments show that the Decis tree will continue to flourish, and will remain in business as a familiar emblem”, is how Kai Wirtz outlines the innovative potential of Decis. It looks as though the future has only just begun.