Uso conjunto de enemigos naturales y plaguicidas: necesidad de establecer la compatibilidad de los plaguicidas

• Autores: Elisa Viñuela Sandoval
• Localización: Phytoma España: La revista profesional de sanidad vegetal, ISSN 1131-8988, Nº 144, 2002, págs. 154-159
• Idioma: español
• Texto completo no disponible (Saber más ...)
• Resumen

  • In the last years, all the developed countries have expressed their concern about the quality of the current productive systems, and about the environmental impact of pesticides. Accordingly, present trends in agriculture in the European Union Countries (UE) are focusing on the adaptation of traditional productive systems to those of sustainable agriculture, having as objective the production of enough amounts of high quality foods and fibers, but in a socially and profitable way and without harming the environment.

    Crop Protection is an essential part of productive systems and the current objectives in the UE are: to decrease the use of conventional pesticides and to expand the use of Integrated Pest Management (IPM) techniques. Modern trends in IPM worlwide, are focusing on the joint use of pesticides and beneficial organisms, because it is well known that natural enemies play a key role in agricultural ecosystems, helping to maintaining pest populations densities at values much lower than those reached when they are not present. However, the joint use of pesticides and beneficial organisms has a problem: enemies are usually much more affected by treatments than pests. Therefore, a previous and essential step for succeeding on their joint use, is to ascertain the side-effects of pesticides on them.

    There are two kinds of studies: those aiming at producing information for IPM, and those aiming at getting pesticide registration in the EU.

    In Europe, the pioneer organization on the study of side-effects of pesticides on enemies, has been the IOBC. Its working group Pesticides and beneficial organisms started its activities as early as 1974, with the objective of giving support to IPM throught the identification and correct use of pesticides, which are compatible with natural enemies. Since, then more than 30 standard methods to measure side-effects on enemies (arthropods, nematodes and fungi) has been developed, and more than 160 pesticides have been evaluated in different enemies.

    IOBC recommends to test side-effects of pesticides on 4 representative enemies per crop. Its standard methods are sequential: they start on the lab with the exposure of enemies to fresh pesticide residues using cages where exposure is maximum, use commercials and the maximum field rates, and test both the most protected and the most exposed life stages of enemies (inside parasitized hosts and adults for parasitoids, and adults and larvae or nymphs, for predators); follow with extended semi-field studies using plants.

    Apart from this standard methods where enemies are exposed to residues, there are many other studies to be done in the lab to totally ascertain the toxic effects of pesticides on beneficials. Among the possible studies are the influence of: other exposure methods (ingestion, contamination vía the food chain, topical application); of different doses, of different formulations (especially for botanical pesticides), and so on. Moreover, more basic studies can also be done to advance on the knowledge of the mode of action of new pesticides, for example using electron microscopy of 14C- pesticides.

    Ecotoxicological studies for registration purposes in the UE, are compulsory since the directive 91/414/CEE dealing with the commercialization of pesticides in the member countries came into force. This studies follow at present a guidance document and have important differences with the IOBC. Ther general principles are as follow: studies also start in the lab, but using two indicator species, the braconid Aphidius rhopalosiphi De Stephani-Pérez and the phytoseiid Typhlodromus pyri Scheuten; enemies are exposed to fresh residues of commercials on glass plates; hazard quotients in-field and off-field have to be calculated, where lethal fifty responses (LR50) are considered; mitigation measures can be applied before performing higher tiers; in higher tiers, a non-sequential scheme can be followed performing experiments in semi-field, field, extended laboratory, and so on; in higher tiers one or more enemies should be used chosen among the recommended species Orius laevigatus Fieber, Chrysoperla carnea (Sthephens),Coccinella septempunctata L. or Aleochara bilineata Gyll.

    In conclusion the joint use of pesticide and beneficials is possible if we identify the selective pesticides, and we modify the use of those harming the enemies, being a pre-requisite the perfect konwledge of biology and ecology of pests and enemies.