Research Areas

Integrated Pest Management 1998-2001

Researcher: Miguel Borges

INTEGRATED PEST MANAGEMENT

Tritrophic Interactions on Soybean: Genetically Engineered Plants and its Possible Changes in the Tritrophic Chemical Communication

ln 1987, when the "National Academy of Sciences" (NAS) considered a redefinition of the term biological control where the use of modified organisms, genes or products of genes would be included to reduce the effect of undesirable organisms (pests), a certain discomfort was caused, mainly in the ecological bases of the biological controL The current paradigm for commercialization of biocontrol agents has as base the chemical modeL with emphasis in the main cultures are steady, cheap and the products are easy to be upscaling for use. ln this model, the agents of biological control do not incase themselves easily. As mentioned for the " Society it will be Invertebrate Pathology " the biological control is in crossroads, therefore the first ideas of that agents of biological control would be important tools for the Integrated Pest Management (IPM), are not materializing. Thus, a new paradigm is necessary for the next century, having as base the biological realities, where new strategies are necessary to solve the problems of production, formulations, distribution and application of agents of biological control, including, among others, genetically engineered plants (transgenics).

Recently, for cultures of large-scale production, as for example the soy, the use of the l.P.M is recommended, in which the techniques of biological control are seen as a valuable instrument. The use of natural enemies for the control of pests is sufficiently promising and in the long run it will be able significantly to reduce the use of insecticides in the culture.

The plants do not only vary its resistance the herbivore insects (pests), but also vary in its attraction and retention of entomophagous species (beneficial insects). The current reality of research of engineered plants, brought to light the concern the interactions between transgenics plants and parasitoids and predators, or either the influence of its volatile ones in the third trophic level.

The plants can answer to the attack of insects pests for the production of volatile that they attract the natural enemies of these pests, phenomenon this known as indirect defense of the plants. These volatile can vary inside of the same species of plant that is attacked by different species of pests. These volatile can be a decisive factor in the extermination (reduction) of pest populations. The volatile produced by the plants, when attacked by pests, can supply information on the species of plant, the cultivate, species and stage of the pests that infest the plant, being therefore more trustworthy to the natural enemies, than the volatile of the plants related with general damages (mechanics).

The volatiles are different of those emitted in response to mechanical damages and terpenoids are a major class among the herbivore-induced na tural enemies’ attractants. The attractants of natural enemies are produced at the site of herbivore damage, as well as in systemically throughout the plant. Cues (chemical signals/ of the pests are not perceived by the natural enemies at a distance, but the volatile of plants, induced by the pests, increase detectability enormously. Therefore, herbivore-induced vola tiles are an essential information source for seeking behavior of the natural enemies.

The success in the development of semiochemicals for the tritrophic interactions can lead to a new strategy of pest control into the IPM. The use of kairomones, for example, can be important in the increase and the conservation of the natural enemies in agriecosystems; the synomones may be extremely useful in the location of the habitat for parasitoides; the alarm pheromones can improve the effectiveness of control agents, for inducing a bigger mobility in the insects. magnifying the possibility of contact with toxic pesticides; and the sex pheromone can be used for monitoring, mass trapping and disruption, as currently are used in other countries such as United States, France and Japan. Inside of this concept the use of semiochemicals as coadjutant in the IPM, has consisted in one of the most promising alternatives in this area in the last times, for the easiness of being able to act integrated to several other measures of pest control besides the tritrophic interactions.

This work intends to integrate biological, behavioral and chemical studies as method to verify possible alterations in the chemical communication in the three trophic levels (tritrophic), induced by transgenics plants. Or in other words, to study plant/herbibore/egg parasitoid relationships in conventional versus genetically engineered soybean.

GENERAL OBJECTIVE

  • To verify if the process of engineered plants with the intention to magnify its Direct Defense (for the production of toxins, repellent and reducing of digestion against herbivores) can influence, negatively, its Indirect Defense, or either in its efficiency of attraction of the natural enemies of the herbivores.


SPECIFIC OBJECTIVES:

To verify if:

  • The plants can respond to the attack of insects pests by producing volatiles that attract the na tural enemies of these herbivores.
  • These volatiles can vary inside of the same species of plant that is attacked by different species of pests.
  • These volatiles can be a decisive factor in the extermination (reduc tion) of populations of pests.
  • The volatiles produced by the plants, when attacked by pests, can supply information on the species of plant, the cultivate, species and stage of pests that infest the plant being, therefore, more trustworthy to the natural enemies than the vola tiles of the plan ts related with general damages (mechanics).
  • Transgenic soybean presents about 2 to 3% more fat acid, which do not appear in the conventional soybean. Which is the effect of this new biochemical composition for the third trophic level?