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The value of biorationals in pest resistance management

Certis Europe, biorationals specialists, have established partnerships with major fresh produce growers in Spain in their project ‘Growing for the Future’. They have worked together to develop Integrated Pest Management programmes combining conventional and biorational products that make an important contribution to resistance management, while minimizing residues of pesticides on the produce.


Oscar Tenorio, Marketing Manager, Certis Spain and Portugal

Certis leads the offer of biorational products for fruit and vegetables in Spain. These are defined as “registered plant protection products generally derived from the natural environment, offering improved benefits for plants, people and the planet, which are increasingly important factors for Integrated Crop Production to satisfy requirements of the value chain and consumers”.

Farmers and technicians like to use biorationals because they have a very positive residue profile: the active ingredients do not create a residue as they are naturally occurring substances (e.g. maltodextrin in Eradicoat); or they can be degraded quickly and easily (e.g. natural pyrethrins in Breaker); or the active is not actually applied to the produce (e.g. pheromones for mating disruption in Cidetrak).

Biorationals are regularly used at any time in organic production or in Integrated Pest Management at the end of the crop cycle close to harvest of the produce – as they have no residue issues - so it is possible to use conventional products at the beginning of a programme and biorationals at the end.


Healthy fruit produced using Growing for the Future programmes

Another important reason for the use of biorationals is that, generally speaking, they are compatible with the use of beneficial arthropods as a complementary tool to manage pests (e.g. Bacillus thuringiensis used for Turex targets only lepidopteran pests and has no impact on pollinators, predators and parasitoids of the most important pests). In addition biorationals pose a lower risk to workers applying the products, bystanders and consumers of the produce. In fact they have a significantly better environmental profile overall.

But, something that is not always taken into consideration is the contribution of biorationals to resistance management.

In intensive farming, especially in horticulture, pest pressure is very high and it can be necessary to treat a crop a number of times with crop protection products. Pests such as thrips, white flies, aphids, leafminers, caterpillars, mites and rust mites produce multiple generations per crop. Diseases such as downy and powdery mildew, botrytis, etc. can develop easily in a crop under certain climatic conditions and the most effective way to control them is to use fungicides in a preventative way when such conditions prevail. Bacteria and viruses can cause catastrophic damage and it is very important to avoid their spread.


Courgette production

Due to the stringency of the registration process, there are today fewer and fewer available active substances and modes of action for insecticides, acaricides, nematicides, fungicides and bactericides. Most new active substances that are developed act on a single point of a metabolic process: they tend to be very selective and in many cases unique to the pest to be controlled. This is good as they are quite specific (and therefore avoid collateral damage to other species) but it also means that the pests can easily develop resistance to the active. The reduction of available products and the potential for the development of resistance to new actives represents another serious challenge to growers.

Managing resistance is one of the most important contributions biorational products can make. In many cases they have a different mode of action from the conventional products. They act in multiple sites which makes it more difficult for the pest to develop resistance: for example Cu2+ (from copper compounds as Kocide) blocks multiple enzymes of fungi and bacteria that lead to a disorder of many metabolic processes in the interior of the cell. In some cases their mode of action is physical, as with maltodextrin (Eradicoat) that covers the spiracles the insects use to breathe; or Bacillus amyloliquefaciens (Amylo-X) or Thrichoderma sp. (Tusal) that cover the surface of the vegetable preventing attack of disease pathogens. They can be natural pathogens of the pests, as in the case of Beauveria bassiana (Botanigard), a natural fungus that causes a disease in many insects and mites; or Bacillus thuringiensis (Turex) that colonizes the intestine of lepidopteran species. No recorded instances of resistance have been found to these pathogens.

Even where they have a similar mode of action, biorationals have the advantage that they can be used without the risk of administering a sub-lethal dose. For example natural pyrethrins (Breaker) extracted from chrysanthemum have the same mode of action as synthetic pyrethoids but they degrade easily and the time for a sub-lethal dose that could promote resistance is so short that it is almost impossible for this to happen, which is not the case with synthetic and more persistent pyrethroids.


Cucumber production under inspection

Nor is it possible for resistance to develop to pheromones. The pheromone used for mating disruption is a chemical synthetized substance identical to the substance that females of the insect release to attract males for mating and reproduction. By creating an atmosphere saturated with this substance, males cannot detect where the females are. If the population were to create a mechanism of resistance that mechanism would effectively reduce the mating process and the population would not survive: no reproduction = no survival.

Certis is promoting the use of biorational products through its collaborative projects, ‘Growing for the Future’, in the production of fruit and vegetables in Spain. These projects have developed Integrated Crop Management programmes with horticultural partners to promote best practice and to produce in accordance with the stricter requirements of consumers and European Food Retailers. The project is now moving successfully from horticultural crops (tomatoes, cucumbers, peppers, aubergines, etc.) to fruit crops such as table grapes, berries, peaches, etc.


Tomato production

In these programmes the use of Certis’ Biorationals is critical to grow produce in many cases without detectable residues or with less than three active substances detected, but always under 30% of the EU-Maximum Residue Limit, as is demanded by the European Food Retailers. During the discussions about the production protocol to be used in the crop, one of the crucial factors is also how to avoid resistance to the essential active substances used and this is where the Certis contribution is so important. For example:
  • It is a common practice to use fungicides by drip irrigation in greenhouses for vegetables, especially for the control of powdery mildew. The risk of promoting resistance is very high due to the long period of time with sub-lethal dose in the plant. In this regard Certis promotes products like Armicarb (Potassium H carbonate).
  • The use of Botanigard (Beauveria bassiana) disrupting the cycle of pests such as white flies, aphids and thrips minimizes the risk of resistance to conventional products.
  • The use of Eradicoat (Maltodextrin) to control resistant rust mite and white flies in vegetables thanks to its physical mode of action.

This article appeared in AgriBusiness Global.

For more information:
www.certisagrosostenible.com

Publication date: 7/12/2018

 


 

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