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vol.24 número3EFECTO DE LA DENSIDAD DE POBLACIÓN Y LA FERTILIZACIÓN SOBRE LAS CARACTERÍSTICAS DE LOS FRUTOS DE ALGODÓN (GOSSYPIUM HIRSUTUM L.)O EMBRIÃO DE THYRINTEINA ARNOBIA (LEPIDOPTERA: GEOMETRIDAE) PODE PRODUZIR PROTEÇÃO AO PARASITISMO DE ESPÉCIES DE TRICHOGRAMMA? índice de autoresíndice de assuntospesquisa de artigos
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Idesia (Arica)

versão On-line ISSN 0718-3429

Resumo

CEPEDA-PIZARRO, Jorge; VEGA, Solange; ELGUETA, Mario  e  PIZARRO-ARAYA, Jaime. SOME METEOROLOGICAL EVIDENCE EXPLAINING THE ELASMODERUS WAGENKNECHTI OUTBREAKS (ORTHOPTERA: TRISTIRIDAE) IN THE SEMIARID REGION OF CHILE. Idesia [online]. 2006, vol.24, n.3, pp.49-63. ISSN 0718-3429.  http://dx.doi.org/10.4067/S0718-34292006000300007.

In the rangeland areas of the Chilean transitional desert (25-32° Lat S), there is a group of orthopterous species that, under certain environmental conditions, irrupt demographically. One of these species is Elasmoderus wagenknechti (Liebermann) (Orthoptera: Tristiridae), an endemic and eremic species to Chile. The objective of this work was to document, from a meteorological point of view, the irruptive events (outbreak onward) occurred in some sites of the Combarbalá area (31°10' S, 71°00' W) in the years 1970, 1996, and 1999. Our working hypothesis was that both rainfall and temperature could have played a role in triggering these outbreaks. To document the hypothesis, we examined the thermal and rainfall patterns of the outbreak year as well as those shown by the 2 previous ones. AOV-tests revealed differences in grasshopper densities among sites for a same outbreak year and between years. Average densities were estimated between 10-50 ind/m2 in 1970; in 1996 and 1999, in turn, these values were much lower (0,17-0,37 ind/m2 and 0,49-0,58 ind/m2, respectively), probably due to heavy chemical control. Regarding our hypothesis, although the annual maximum values of temperature slightly tended to be reached earlier in the summer season in the years previous to the outbreak, no evident deviations were detected between this thermal behaviour and the historical thermal pattern of the area. Annual rainfall registered during the outbreak years and the year before was lower than the 30-years mean value. The recorded rainfall of the second year before was, however, inconsistent. It was drier in the 1970 and 1996 outbreaks, but moister in the 1999-outbreak. Some deviations were observed between the 30-years monthly historical pattern and the monthly rainfall pattern of the outbreak years. The meteorological data available to date support the idea that relatively high summer temperatures, recorded rainfall lower than the historical mean value, and deviations from the monthly rainfall pattern may induce E. wagenknechti outbreaks. This evidence may be obscured because heavy chemical control applied early in the season.

Palavras-chave : Orthoptera; rangeland insects; population outbreaks; arid lands; biometeorology; Chile.

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