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Ana Ollo Hualde

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2006/1/4

THESIS: Bioinsecticide for market garden produce from Almeria

The Spodoptera exigua multicapsid nucleo-polyhedrovirus (SeMNPV) is one of the most promising alternatives to the use of chemical products for combating a pest that shows itself mainly in greenhouses in Almeria (southern Spain). This is the conclusion of the PhD thesis recently defended at the Public University of Navarre by the agricultural engineer, Rosa Murillo Pérez. She undertook a study of this pathogen in the protected crop zone of Almeria in order to select the strain with the best properties as an insecticide. Nucleo-polyhedroviruses are ones which have a great potential as bioinsecticides in agricultural and forestry pest control programmes.

An alternative to chemical insecticides

The larvae of the Spodoptera exigua lepidoptero are particularly concentrated in temperate and subtropical zones. In Spain, Almeria is one of the locations that most suffers from the effects of this species. Producers of crops such as peppers, watermelons, melons, cucumbers, marrows and aubergines are faced with considerable costs arising from attacks by these types of insects. Today, there does not exist any effective commercial biological product for the control of the pest. This is why the producers of Almeria have turned to chemical insecticides. However, many of these substances have turned out to be ineffective because the larvae easily develop resistance. Moreover, the application of the pesticides does not always respect the chemical waste levels permitted for fruit and vegetables and may thus give rise to noxious effects on the natural environment.

According to the author, bioinsecticides are a solid alternative to chemical products. The advantage of bioinsecticides is that they are specific, they can be made economically and are effective in the control of this pest. On the one hand, they do not leave any noxious waste on the crop and, on the other, they can turn out to be cheaper, given that its efficacy reduces the number of applications needed to control the pest.

Another benefit of this virus is its compatibility with other control methods being employed for simultaneous pests and, thus, it can be included in integrated handling programmes. Nevertheless, its negative side is that, unlike chemical pesticides, this pathogen does not exterminate the larvae rapidly, but produces a visible effect within two or three days, time in which the larvae continue to cause crop damage.

In her thesis, the author studied the abundance and biodiversity of the SeMNPV populations in Almeria using samples of soil and of S. exigua larvae collected from an area of some 40,000 hectares of greenhouses over a period of 18 months. One of the reasons that could possibly explain the persistence of the virus in Almeria is that the crops are covered by plastic.

Marketing of the bioinsecticide in the short term

Various improvements to boost the insecticide activity of the virus are currently being studied. In concrete, in this thesis it was shown that the addition of an optical lustre to the SeMNPV increased its virulence. In the research, it was shown that the incorporation of this product slowed the growth of the larvae and favoured the pathogenic action of the virus.

To date, this virus has been successfully applied in various regions of the world such as North America, Thailand, the Netherlands, Taiwan, Egypt, India and Japan, although this would be the first time that a bioinsecticide of these characteristics has been used in Spain.