Biologic control

One of the most important reasons to restore and/or maintain biodiversity in agriculture, is providing a variety of ecological services. Within these services the regulation of the abundance of undesirable organisms within the system is through predation, parasitism and competition. In this sense, biological control can be considered a valid strategy to restore functional biodiversity within agricultural ecosystems.

Biological control occurred on the world stage during the nineteenth century, when the scientist Charles Valentine Riley introduced a beetle and a parasitoid fly from Australia to California to control the plague of Icerya Purchasi that was affecting the cultivation of citrus in the state. However, biological control has older roots, knowing Chinese in the fourth century that show biological control strategies for growing mandarins treated. The use of biological control essentially seeking to restore the ecological balance, which can be seen disturbed by human activities in the agricultural ecosystem. This is achieved through the use of living organisms or their metabolites, to eliminate or reduce the damage caused by harmful organisms. In most insect groups are entomophagous species that feed on other insects as predators or parasites.

Because of the advantages that these species entomophagous presented for agro-ecosystem, it is not surprising that the natural evolution of agricultural production systems has led in recent years to control methods of pests and diseases that focus on the use of these organisms as agents of control populations of harmful insects.

 Such strategies have emerged as more rational and integrated with the environment alternatives, based on the precepts of sustainable development and biodiversity conservation.

As is known the use of chemical pesticides in pest control you have a number of side effects as is the rejection by the target insects after a while also high levels of toxicity pollute the environment through accumulation and ability to cause the death of other species of insects and animals makes them a risk to environmental health.

Contrary to this, strategies based on biological control organisms possess the advantages of high specificity (not affect other species), relatively low cost and low environmental impact, and are supported by several scientific studies that have demonstrated the feasibility of using microorganisms and other entomopatógenos for biological control.

Biological control and zompopas

A mature colony of Atta sp., Commonly called zompopero, may contain more than 5 million ants and consume a quarter ton (dry weight) of plant material per year, occupying more than 20 cubic meters total area. There is an evolutionary trend in herbivorous insects towards specialization in a small number of plant species of a few families, however zompopas and its symbiotic fungus act together as a generalist herbivore, being able to feed a large number of species and different plant families. This is due to the combined abilities of the two bodies, as ants exceed anti-fungal plant barriers while the fungus neutralizes toxins produced by insect plants. For this reason, zompopas cause losses of millions of dollars annually to the agricultural industry in Latin America.

The most commonly used strategy to control zompopas is treatment with granular insecticides as sulfuramide (Mirex-S®) and diflubenzuron (Formilin®). However, these compounds have multiple disadvantages, including rejection by ants and recovery of colony weeks after application. These features work as justification for methods recently proposed biological control, whose implementation has more durable than chemical treatments results.

One is based on microhongo Escovopsis (Hypocreales: Ascomycota), which is a specialized parasite that directly consume the fungus cultivated by the ants. Because of the dependence of the fungus ants, the result is a dramatic reduction in the survival and reproduction of the colony. Escovopsis is quite virulent and highly specific zompopas, as has not been isolated from any other natural environment. This reinforces the point that the evolutionary history of this pathogen, ants and the fungus associated with these in the fungal gardens anthills have been intertwined since millions of years ago.

The implications are that you have an agent specific control, and has interacted with the target species for a long time so that the risks of excessive control by Escovopsis and possible unknown effects of deleterious impact for ants and the fungus are reduced .

The second strategy is based on aversion manifesting the zompopas to the waste material discarded by the colonies. A mature colony can discard up to 200 kg (dry weight) of waste material per year, which is placed by most species in chambers several meters underground, or in some cases, such as the Atta species colombica present in Costa Rica's Osa Peninsula, in conspicuous mounds of external waste. The implemented control method based on waste materials is based on implemented by the natives of South America.

In this, the material is used as a repellent, placing it around the trees they want to protect from ants, which prevent the discarded material. Why this aversion states could be due to the presence of pathogenic microorganisms.

Here are some samples of studies on biological control of leaf-cutting. However more research efforts are being carried out in order to implement a Escovopsis and identify entomopathogenic microorganisms in the future to have a suitable biological control against leaf-cutting ants.

References
Daena: International Journal of Good Conscience. 1 (1): 82-89. March 2006 - September 2006. ISSN 1870-557X.

biocontrol a sustainable form of pest control (control Biological way of sustainable pest control) Badii, M. H. y J. L. Abreu *