dimanche 12 mai 2019

146- Alternatives to pesticides -5- Trapping


The use of traps is probably one of the oldest hunting methods, widely used by humans.
The principle is quite simple. It consists first of all, in knowing well the preyS, their rhythm of life, their habits, their food, their path of passage, their strengths and their weaknesses.
From there, traps are set, so that the prey is irresistibly attracted, or across its usual path of passage.
In any case, the purpose of trapping is usually the death of the animal, sometimes its capture to drive it elsewhere.

Modern agriculture has adopted this ancient technique to reduce or eliminate the damage of certain animals that are harmful to agricultural crops.

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When we talk about trapping in agriculture, we think in the first place of rabbits and other rodents like voles. And it is true that we can use this technique to reduce their damage.
Some models of vole traps are for example marketed to be placed in the galleries, in order to use it to replace the usual poisoned baits.
It may seem cruel. Yet these modern traps are very effective and the death of the animal is almost instantaneous, avoiding its suffering much more than with the majority of traditional artisan traps or with poison baits.

In the end, the focus is on vertebrate control rather than population control.
And trapping has the merit of reducing the risk of killing non-target animals, such as their predators (raptors, snakes or carnivorous mammals) by indirect poisoning.

But this technique has mainly developed during the last 3 or 4 decades with the needs of crop protection against pest attacks.

The trapping technique is widely used for monitoring pest populations through the capture of individuals in a limited number of reference points. It allows the farmer to assess the evolution of the risk, and thus to implement the measures he has planned at the most appropriate time.
This technique is very widely used in IPM (integrated pest management) and integrated production and in organic farming to locate as accurately as possible the insecticides necessary for the protection of the crop.
The attractants used are either sexual pheromones (which I told you about in the previous chapter http://culturagriculture.blogspot.com/2019/03/145-the-alternatives-aux-pesticides-4.html) used in particular for the monitoring of Lepidoptera, numerous on many crops, either food-based attractants as used for Mediterranean fruit fly (Ceratitis capitata), or obstacles, such as sticky strips to monitor mealybug larvae, or stained plates or strips of color (usually yellow or blue) for whiteflies or thrips. There are also colored traps or light traps for certain uses, as is the case for domestic mosquito trapping.

The design of the insect trap is also very important in its effectiveness, and depends both on the target pest and the bait employed.
In the case of flies for example, they must go in without having the possibility of going out. So we use the principle of the fish trap that is to say that once entered the trap, it is almost impossible for him to find the opposite way.
We will play on the shape of the trap, its color, transparency or opacity of the materials used.
Still in the case of the fly, it is attracted by the yellow color. Inside, we place an alimentary bait whose smell will guide it to the entrance hole, located on the yellow and opaque part. The top of the trap is made of transparent material. Once inside, the fly is attracted by the light, so towards the transparent part, and thus does not find the exit.
The same principle is used to capture wasps in gardens.
A pellet impregnated with insecticide, synthetic or natural depending on the case, kills the insect inside the trap. In some cases, it is the alimentary bait in itself, liquid, which will kill the insect by drowning. In other cases, the pheromone pellet is placed on a stuck plate from which the insect cannot escape.

The same principle is used in the technique of mass trapping, which consists in using traps of the same type as for monitoring, but in very large numbers, with the aim of attempting to capture almost all the individuals present, thus avoiding the use of insecticides in direct contact with the crop.
The technique works well in some cases, bad in others.
In most cases, crop damage is produced by insect larvae. Therefore, adults should not be allowed to mate and reproduce.
Efficacy is generally good if you catch mostly females.
By cons, if the attractant catches mainly males, we cannot avoid that females, fertilized outside the plot to protect, come to lay their eggs on the sensitive crop.

As with the sexual confusion, mass trapping is based on a long and extensive scientific research work from which these techniques can be developed avoiding the use of pesticides in direct contact with the crop.
In the same way, the farmer must have a very good knowledge of the situation of the crop and the phytosanitary risks present.

These techniques are very selective and thus make possible to minimize the undesirable side effects of crop protection.
They are likely to grow strongly in the coming years.

Picture: http://image.made-in-china.com/2f0j00sSWaybQzJVrE/Yellow-Blue-Sticky-Trap.jpg

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