Integrated Pest Management : a more environmentally friendly method (part 2)

Preventive measures and crop surveillance

The aim here is to intervene before pests become a threat to agriculture. This is the first and most important step in IPM. It mainly involves appropriate agricultural practices, such as modifying the habitat of pests.

Among these methods, an Ivorian entomologist interviewed in interview No. 2 “Prevention is better than cure” cites methods such as plowing or weeding and crop rotation. In interview No. 4, “Cultivation methods, valuable prevention tools,” another agronomist interviewed in Mali recommends early sowing, soil cleanliness and maintenance of the area around the plot. A particularly effective cultivation method is the use of varieties that are resistant to certain insects that attack specific plants. In the case of cotton, for example, as we learn in interview No. 2, a variety with hairy plants prevents insects from clinging to the stem and thus reduces the possibility of infestation. Pheromone traps that attract and trap insects are also discussed; pheromones are chemical substances produced by some insect species (probably by many more species than our current knowledge suggests) to enable their members to communicate with each other. Often these are sex pheromones that the female produces to attract a male. Lepidopteran (butterflies and moths) pheromones are the best known and these chemical messengers can be produced commercially by mixing and synthesizing appropriate chemicals. The chemicals used to make the traps are usually introduced into a rubber baffle (a small rubber capsule), which is placed on a sticky trap to attract male moths.

The Ivorian entomologist interviewed in Interview No. 2 “Prevention is better than cure” also cites the example of a very traditional method used in Côte d’Ivoire, which consists of rubbing a stick with hedgehog grease, which attracts aphids that attach themselves to the wood and die because they are stuck and can no longer detach themselves. However, this interview does not mention the so-called “physical protection” measures such as bagging the fruit, nets against birds or protective belts on the trunks.

In this respect, scarecrows are a widely used example, but as the agronomist interviewed in interview 3, “Surveillance is essential”, they are only effective for a short time, as birds in particular soon realize that they are not real humans! Other methods such as poisoned baits or traps seem to work better on small farms. Other deterrents include physical surveillance, such as chasing birds or rodents away when they are spotted by shouting from the field and sounding the alarm. These methods are commonly practiced by African small-scale farmers, but the agronomist emphasizes the importance of monitoring fields not only during the day (morning and evening) but also at specific times of the year that correspond to the different vegetative stages of the crops.

3 Pest identification

Very often, despite the general prevention and monitoring measures discussed in interviews 2, 3 and 4, the farmer still finds himself confronted with pests and experiences damage in his fields. To remedy the problems caused by the pests and to prevent the damage from spreading, the farmer must try to recognize the signs left by the pests, i.e. know who or what he is dealing with, because effective pest control is based on a thorough understanding of the pest. This is the subject of interview No. 5 “Finding out who you are dealing with”.

For this identification, the farmer’s sight, hearing, smell and touch will be used first. For example, if there is an infestation of rodents, the farmer will notice that the seeds are gnawed and as it is the germ that the rodents eat, the emergence rate will be reduced; If the maize is being attacked by birds, the farmer will see that the silks and spathes have been cut off, and he will be able to see the debris of the spathes underneath the plants from a distance; or if the maize is being attacked by insects, such as caterpillars, which secrete substances that are often white, the farmer will know from these signs that there is a caterpillar attack on the young plants, and will be able to intervene. Other clues are the characteristic noises of the insects that are often observed on stored foodstuffs. This is the case of weevils, for example: when one enters a storage area of heavily attacked corn, one hears small noises, like whispers.

This sensory monitoring can be complemented by other methods of identification, such as traps containing attractive substances like pheromones, which can be placed in places where the pests pass through and fly around, and which allow the extent of the infestation to be determined. It is important to specify, however, that the use of these methods is still limited because of the technical difficulties they cause.

In any case, once the identification has been made to determine the species, developmental stages, size and location of the pest population, the farmer can then choose a particular control method.