The Impact of Pesticides - Academy Publish

Another important example in the soybean crop is the application of insecticides onthe border of the field mixed with sodium chloride (common table salt) to controlstink bugs. This practice is effective because the stink bugs are concentrated on theedges of the crops at the beginning of the infestation and the salt acts leading theinsect to a longer feeding period within those areas and, consequently, increasingthe contact with the product. These techniques allow the spatial separation of theinsecticide and beneficial arthropod, thus preserving the latter of poisoning thatwould occur if it came into contact with the chemical.An example of temporal ecological selectivity is the not applying insecticides in themiddle of the day, avoiding the hours in which pollinators most visit the flowers,thus obtaining a separation in time between the product application moment and theperiod in which the beneficial arthropods that, otherwise, would be exposed tocontamination. These practices allow that a chemical product, even when nonselectivephysiologically, has an ecological selectivity, preserving this beneficialarthropods in the area and, consequently, minimizing the negative impact of thechemical control on pollinators.As we can see, the ecological selectivity is only possible due to differences inbehavior or habitats between species, enabling the product to be in contact with agiven species and not with another. This strategy is based on the ecologicaldifferences between pests, natural enemies and pollinators and requires a thoroughunderstanding of the bio-ecological aspects of pest and beneficial arthropods whichsometimes might not be available for some important species.How the studies on selectivity of agrochemicals to natural enemies can aid on thereduction of the negative impact of pesticides of the soybean agroecosystemIn classifying a chemical as selective or harmful to beneficial arthropods is of greatimportance to consider all possible aspects. Worldwide, studies of selectivity havebeen the subject of many discussions, many times without reaching a common senseconcerning methodologies or the standardization of the procedures used to evaluatethe side effects of pesticides on beneficial organisms. This lack of consensus createssome contradictions in the results and conclusions found.Some of the causes of these contradictions are the many tests carried out under fieldconditions, where the direct effects of the toxicity of the insecticide were not clearlydefined. Many times, the elimination of the predator is due to the suppression oftheir food supply (insect pest). Different species may also respond differently topesticides, in addition to the differences in the dosages of the products and of theinsect developmental stages. As earlier mentioned, an evaluation methodology thatconsiders all these bio-ecological differences is extremely necessary. In this context,in 1974, a group to work for the international scientific cooperation in the study ofselectivity of pesticides to beneficial organisms, the International Organization ofBiological Control (IOBC) was formed. One of its main goals is the globalfomentation of selectivity tests based on a standard methodology. Since then theIOBC has promoted studies to standardize selectivity tests. According to thisorganization, the insect must be first submitted to an extreme contaminationcondition and if a high percentage of the population does not die, then the productcan be considered harmless. Otherwise, it should go through complementary testsunder greenhouse conditions and then in the field.Among the species of natural enemies studied some, in addition to their potential ascontrol agents, present a high degree of compatibility with the combined use ofchemical compounds as, as for example, the egg parasitoids. These natural enemiesare the insects that have attracted more interest worldwide, for killing their hostsAcademyPublish.org - The Impact of Pesticides179