Diversidad y control biológico de insectos - CyberTesis UACh ...

Keywords: Pasture pest; Principal curve response; Entomopathogen; Non-target effects;
Guilds.
Introduction.
Three millions hectares are dedicated in Southern Chile to support beef and dairy cattle, the
most important agricultural activity in that area of the country. Yearly, about 10% of this
area is sprayed with synthetic insecticides to control the pest Dalaca pallens (Blanchard)
(Lepidoptera: Hepialidae). The larval feeding activity of this moth reduces severely the
pasture yield and high infestations can produce the death of the plants. Growers keep this
pest in check mainly by massive spraying of pyrethroids and insect growth regulators
(IGRs). However, more alternatives are needed to design a sound and robust control
scheme under the integrated pest management approach.
Beneficial arthropods play an important role in controlling crop pests and thus the
selectivity is a fundamental component of IPM in order to minimize disruption of the
ecological community, especially natural enemies. The application of broad-spectrum
insecticides often disturbs the activity or abundance of natural enemies and thus depresses
the natural control of pests. In addition, species other than predators or parasitoids are being
recognized as useful and necessary for a proper functioning of agroecosystems (Kenmore et
al., 1984; Settle et al., 1996). Both toxicological and selective properties of a material must
be evaluated before to include a new product in the IPM of a pest.
The fungus Beauveria bassiana (Balsamo) Vuillemin is a world-wide entomopathogenic
organism and is used to control several insect pests in many countries. The
Entomopathogenic Organisms Collection held at the Instituto de Investigaciones
Agropecuarias (INIA) includes more than three hundred B. bassiana isolates collected
across the country. The isolate B-931, originally collected from a field-parasitized larva of
D. pallens, has been under research for more than 5 years to assess its efficacy against D.
pallens in laboratory, small field and large field experiments (Cisternas, unpubl. * ). A field,
large plots (1 ha) and replicated experiment carried out in 2003 (Cisternas, unpubl.*)
showed that the application of ten grams of spores per ha (10 12 spores per ha) caused the
* Ernesto Cisternas, ecistern@inia.cl
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