Organic or conventional treatments against pests

Is it possible to abandon all pesticides in agriculture?

Before the invention of synthetic pesticides, for thousands of years, famines occurred from time to time due to the emergence of real epidemics that destroyed a large part of the crops. Cereal yields were 10 times lower than today. Nowadays, most people who have never experienced these famines have become accustomed to eating their fill every day, without realising that this progress is due to the use of fertilisers and pesticides in agriculture.

Of course, pesticides do not have only advantages. Their intensive use can produce more resistant pests through selective breeding, they are not selective and they can have a negative impact on biodiversity and especially on beneficial organisms. But the vast majority of farmers know that banning all pesticides is a utopia, especially since everyone in agriculture treats them, including professionals who have converted to organic farming, which many French people do not know. According to a survey conducted by Harris Interactive and distributed by the association Alerte Environnement, 50% of French people do not know that organic farming uses phytosanitary products (1); products that are not, however, harmless because of their chemical properties and the doses commonly used to compensate for their lack of effectiveness.

Treatments are therefore unavoidable if the farmer does not want to find himself with insurmountable losses in yield when, for example, the climatic conditions are unfavourable, producing an explosion of a bio-aggressor. It should never be forgotten that plants are also living beings that can be sick and must be treated from time to time in the same way that one treats one’s domestic dog when it is sick.

Worms in fruit or vegetables thrive by digging galleries that facilitate the introduction of particularly pathogenic fungi and bacteria. Don’t expect these worms to deposit their excrement outside to please you because you are a fan of organic produce. These droppings deposited in the tunnels are a source of infection and contain dangerous toxins that spread through the fruit. Certain pathogenic fungi (aspergillus sp. – penicillium sp.) that accompany the attacks of the “apple worm” (codling moth) produce patulin, a neurotoxic, teratogenic, immunotoxic and embryotoxic toxin (2), whose admissible daily dose currently tolerated in food is 0.4 µg/kg of body weight (i.e. a very small dose). It is forbidden to market apple juice if its patulin concentration exceeds 50 µg/kg. The presence of patulin cannot be detected by taste or smell.

When bedbugs move into a house, no one would think that they should not try to get rid of them with a suitable pesticide under the pretext of protecting the environment. Plants are frequently victims of biting insects. Why not protect them with appropriate treatments when other means of protection are not effective?

Are pesticides dangerous? Certainly they are. Just as the sun is dangerous, bees are dangerous, trains and cars are dangerous… But defining a danger is not enough to measure its real impact in everyday life. Exposure factors must also be taken into account. A hazard can be controlled if the exposure factors are well known and controlled with effective protection.

For the vast majority of plant protection products that we use, the fundamental question is whether exposure to these pesticides presents an acceptable risk. This distinction between dangers (capacity of a substance to produce toxic effects depending on the dose) and risks (exposure to the recommended active dose, recommended means of protection, etc.) is very often ignored by those who call for a ban on all pesticides. Their attitude is most often a manifestation of technophobia. Synthetic products are easily suspected while natural substances are adorned with all the virtues without any link to scientific data..

A review of fundamental concepts in agronomy and the use of pesticides

All apple growers know that it is strongly advised not to treat against pests when a fruit tree is in bloom. Even if the tree is covered with aphids, no pesticides should be sprayed. Otherwise, virtually all pollinators will be eradicated. And without pollinators, there is no fertilisation of flowers and no harvest. Treatment against a pest is only possible once all the flowers have disappeared, because without flowers, there is nothing left for pollinators to eat, so they will move on to another food source.

This fundamental concept of agronomy was still being taught more than 50 years ago in all agricultural colleges. But it seems that many critics of pesticides are unaware of this, just as they are unaware that a field of sugar beets can be treated with acetamiprid in the spring because they are not in bloom and are not visited by bees.

Sugar beet, like the edible red beet often grown by amateur gardeners, is biennial and flowers in the second year after sowing at the end of winter. Beets are never harvested after flowering, as they are inedible, except perhaps for pigs when a field has been neglected. This is also why farmers have requested an exemption to use acetamiprid to treat sugar beet against aphids before ladybirds arrive.

These agricultural “reasoning” techniques also incorporate other criteria, such as the choice of molecule and treatment doses in relation to the characteristics of the pest, the number of sprayings required, the priority given to biocontrol methods when they are effective…; the objective being to minimize the impact of chemical treatments on the environment.

Sugar beets, like the edible red beets grown by home gardeners and market gardeners, are biennial and flower in their second year after sowing, at the end of winter. Beets are never harvested after flowering, as they are inedible, except perhaps for pigs if a field has been neglected. It is also for this reason that farmers have requested an exemption regarding the use of acetamiprid to treat sugar beets against aphids before the arrival of ladybugs.

Of course, it is entirely possible that acetamiprid could accidentally end up on wildflowers frequented by pollinators, an argument often used by anti-pesticide advocates, except that a beet field is subject to weed control, another fundamental concept of agronomy that farmers have practiced for millennia to reduce weed competition..

It can also happen that pesticides are accidentally carried beyond a field or orchard. A farmer tries to avoid spraying onto a neighbor’s land, and especially onto a private individual’s, which is against the law, especially since this oversight represents an unnecessary financial loss for the farmer. Nowadays, pesticides are one of the most significant expenses for a farm, and every farmer tries to reduce them. The fewer inputs used, the better for the bottom line. When a pesticide is drifted elsewhere, it doesn’t affect the crops, resulting in a loss of effectiveness that will sooner or later require a costly retreatment. Therefore, spraying should only be done when weather conditions permit, certainly not during windy or rainy periods that would wash the pesticide away.

When should plant protection products be used in integrated agriculture?

Organic agriculture refuses them because they are produced by industry. Deltramethrin (the active ingredient in Decis) was invented by chemists who were looking for a molecule with the same properties as the chrysanthemum pyrethrins allowed in organic farming. Deltramethrin is an insecticide of the pyrethroid family that acts by contact (the pesticide is not introduced into the plant). It acts very quickly on aphids, but has the same disadvantages as the pyrethrins used in organic farming. This insecticide is toxic to bees, fish and freshwater invertebrates. It should therefore not be applied during flowering. As for fish and invertebrates, there is no reason to spray rivers and ponds.

Deltramethrin is metabolised by the microflora when it falls to the soil. But its half-life in the soil is more or less long; from 13 to 72 days (4). In the leaflet of the Société Chimique de France, it is stated that the formulation in the form of a concentrated emulsion of deltramethrin “makes it possible to reconcile good coverage of the plant with high bioavailability” (5). At the doses recommended by the manufacturer, deltamethrin appears to be particularly harmless to birds and mammals. At higher doses, deltamethrin has been shown to be toxic by inhalation (which is also the case for natural pyrethrins registered in organic farming). It is therefore advisable to follow the application conditions specified in the manufacturer’s instructions.

Consequence of the ban on synthetic pesticides for private individuals from 1 January 2019

Some organic gardeners refer to the simplistic idea that nature should be respected by rejecting the cultivation of any vegetable that is not adapted to the local environment. This principle is also mentioned in some books and press articles to justify the ban on pesticides for private individuals since January 2019 (7). If I take a pest such as the Colorado beetle as an example, such a recommendation for home gardeners leads to a ban on potato cultivation in all regions of France..

The reason often given for banning synthetic pesticides is to accuse individuals of not respecting the doses prescribed by the manufacturers. However, the products considered the most dangerous were already banned before January 2019 for non-professional use.

Since synthetic pesticides are banned for private individuals from January 1, 2019, how will they be able to comply with the regulations that require them to intervene if their crops are victims of a formidable pest that is part of the list of regulated harmful organisms?

The ban on synthetic pesticides for amateur gardeners has led to serious plant health issues, which is why many vegetable gardens are being abandoned. There is no effective organic treatment for certain particularly aggressive pests such as the bacterium Clavibacter michiganensis, which causes potato blight, or the Drosophila suzukii fly, detected in France since 2009, which attacks cherries, raspberries, strawberries, tomatoes, etc., and can cause production losses of up to 80%. This fly “is too well established in the country for it to be possible to eradicate it. The use of local parasitoids has not yielded conclusive results.” (8)

The ban on synthetic pesticides, targeting 17 million of our fellow citizens, has had no effect on reducing the volume of pesticides used in France. 5% of the tonnage of active plant protection substances marketed each year in France was used in non-agricultural areas, the remainder being used by farmers. Of this 5%, between half and two-thirds were used by private individuals (9).