dimanche 27 août 2017

113- Plant protection -7- Surgical control


The use of insecticides, synthetic or natural, even if very well applied, always involves negative side effects.
The farmer must protect his crop against, for example, a specific type of aphid. But at the same time, by his aphic spraying, he will eliminate all other present aphids, beetles, lepidoptera and other harmful insects, but also a large number of useful insects (bees, lacewings, ladybugs and other auxiliary insects), and also a great number of insects, neither pests nor auxiliaries, just present, such as mosquitoes or flies.

It's a general spraying, with a product chosen for the targeted problem, but always more or less versatile, thus also acting on non-target insects.

Modern insecticides are not perfect, it would be known, but their side effects have been considerably reduced compared to their elders prior to the years 70-80. Indeed, since that time the legislation, and consequently the search for new molecules, has placed an absolute priority on reducing the direct side effects of pesticides. These include, among other criteria, risks to water, soil, birds, mammals, aquatic fauna and flora, auxiliary insects, but also to health risks for users and consumers.
Nothing is perfect, no doubt, but toxicological and environmental profiles of the current products are, despite their defects, incomparably more favorable than those of the old molecules, most of which are currently banned.
However, the versatility of action of a pesticide remains a serious problem still unresolved. Today, only the techniques of "sexual confusion" or "mass trapping" arrive at an almost perfect specificity, thanks to the use of specific pheromones.

Side effects of insecticides are harmful because reducing the presence of many non-harmful insects reduces the feeding potential of many other animals (rodents including bats, birds, reptiles), and thus biodiversity on the farm.
Reducing biodiversity on the farm reduces predation pressure on insect pests, thus increasing their impact on crops.
In short, it is the snake that bites itself the tail. We spray to avoid damage, but by spraying, we reduce the biodiversity, so the pressure of pests increases and the risks of damage also, forcing to spray more.

This is one of the great arguments of environmentalists, and in this sense they are right. But beware, all this does not prevent that the initial attack, the one that caused the spraying which caused in turn the imbalance, was very real. The farmer then needed to spray, and he probably did it right. The problem lies in the means at his disposal to solve his problem.
It's so true that ecological production must also solve these same problems with insecticides, natural, of course, but not without side effects, with consequences for biodiversity that are often comparable, at least in the short term.

The stupid speeches claiming that "organic can feed the world" or "if we suppress food waste, we will solve hunger in the world", are above all an intellectualization of the concepts, and especially the rejection on others of supposed mistakes.
Yet most of the food waste in poor countries occurs in the fields, due to damage from diseases and insects. And that, in agricultural systems that don't use pesticides.
But that's another debate.

Humanity continues to grow inexorably.
If this is added to the urbanization that is gaining on agricultural land, the effects of soil erosion, which is still too often uncontrolled, and the essential need to master freshwater resources, then the control of food production is undoubtedly one of the major challenges of humanity for the 21st century. And if we speak of mastery of production we speak of reduction of the non-consumable part, thus among others, damage of insects or diseases.
Personally, I have no doubt that in the coming years we will be able to maintain, and probably even increase, agricultural productivity while greatly reducing its negative impact on the environment.
But I don't doubt either that we will continue to need natural AND synthetic pesticides.

And it's now, after this long introduction, that comes the subject of the day, recovered on Twitter https://twitter.com/collemyria/status/900489867108470785

ISCA Technologies' scientific team (https://iscatech.com/), an American company specializing in alternative crop protection technologies (traps, attractants, repellents, etc.) recently presented the results of its research on mosquitoes, so as to minimize the negative effects of mosquito control, in situations where mosquitoes are a real danger by the transmission of many diseases, including dengue, zika, chikungunya or malaria.

"Researchers collected the fragrance of flowers and other plants that produce nectar. Then, they used gas chromatography and electro-triennial detection (GC-EAD) to separate and identify the odorous compounds found there. They exposed mosquito antennas to thousands of these compounds to determine which ones could have a biological effect. They also eliminated perfumes or aromas that could attract bees. Finally, they used a semi-chemical mixture in a matrix containing sugars and proteins to mimic 20 frequent chemical signals that attract mosquitoes by prompting them to feed."

The idea is to achieve a mix of the specific attractant with a modern insecticide. This mixture is applied to specific spots in limited number. The mosquito is irresistibly attracted by the mixture, which eliminates it.
"The mix of chemicals we use to attract mosquitoes is so powerful that they will ignore natural flavors of plants to go to our formulation," says Agenor Mafra-Neto of the research team.

This technique is currently destined for mosquitoes to reduce the incidence of infectious diseases. Moreover, as the article says, "researchers conduct field trials in Tanzania where 93% of the population is in a risk of malaria. In preliminary results, they found that mosquito populations declined by two-thirds in just two weeks in treated communities [...] compared to untreated populations."

This seems to me an extraordinary piece of news.
Extraordinary, of course, for the resolution of diseases transmitted by mosquitoes and for the populations exposed to them.
But extraordinary also insofar as it opens the door to the same work on insect pests for food production. One could then carry out totally targeted treatments, with high efficiency, but extremely reduced negative effects.

This technique is already used in agriculture, for example against the Mediterranean fruit fly (Ceratitis capitata). It is a spot bait treatment. It consists in dispersing small spots of the mixture in the crop which will attract the insect and kill it, with a very low negative impact. It depends on the quality of the bait. If it's powerful enough, the insect turns away from the crop to go on the insecticide spot.

So of course, all this does not necessarily have only qualities. Assuming that in the future we will be able to select specific attractants for all crop pests, we may find ourselves in a situation where secondary insects, now controlled by the versatility of insecticides, appear again with a high incidence, because of the very high selectivity of the technique.
But let's be positive. The experience of sexual confusion, a very specific technique used on a large scale and throughout the world for at least 25 years, had few consequences of this type. It's true that sporadically some "secondary" insects can become damageable but, with some exceptions, the gravity is generally low.

From this type of technique, by similarity to the effects observed for the Mediterranean fruit fly, one can reasonably expect, depending mainly on the effectiveness of the attractant:
- Maintaining or even improving the effectiveness of the protection,
- Reduction of insecticide application rates from 80 to 90% per hectare for spot bait treatment, and more if what works is mass trapping,
- Reduction of insecticide losses by drift to the vicinity of the crop (uncultivated areas, waterbodies and rivers, neighboring crops) or by leaching by rain, by at least 90%,
- Consequently an almost total elimination of the negative side effects of the use of insecticides,
- A combination of these new generation attractants with synthetic insecticides (for duration of action) or natural insecticides (for organic production),
- For some pests at least, the possibility of using the insecticide without affecting directly the crop (application to the cover planting, on sticky patches or in traps), thus a complete elimination of the risk of residues on the final food.

Under these conditions we can expect a considerable improvement in the techniques of application of insecticides and an almost complete elimination of the negative side effects of the use of insecticides.
In the same way that sexual confusion is widely used in both conventional and organic agriculture, it is to be hoped that these techniques will find their place quickly and on a large scale in all farms.

It remains for us to hope that researchers and chemists will make rapid progress in this technique, bringing versatility by increasing the number of possible target insects.
This seems to me to be a major innovation for the evolution of agriculture towards more virtuous production and for more efficient and sustainable food production.

Picture: http://www.maxxum100.com/images2014/slider/2.jpg

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