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Stability of spinosad resistance in Frankliniella occidentalis (Pergande) under laboratory conditions.

Authors
  • Bielza, P
  • Quinto, V
  • Grávalos, C
  • Fernández, E
  • Abellán, J
  • Contreras, J
Type
Published Article
Journal
Bulletin of entomological research
Publication Date
Aug 01, 2008
Volume
98
Issue
4
Pages
355–359
Identifiers
DOI: 10.1017/S0007485308005658
PMID: 18279567
Source
Medline
License
Unknown

Abstract

The stability of spinosad resistance in western flower thrips (WFT), Frankliniella occidentalis (Pergande), populations with differing initial frequencies of resistance was studied in laboratory conditions. The stability of resistance was assessed in bimonthly residual bioassays in five populations with initial frequencies of 100, 75, 50, 25 and 0% of resistant individuals. There were no consistent changes in susceptibility of the susceptible strain after eight months without insecticide pressure. In the resistant strain, very highly resistant to spinosad (RF50>23,000-fold), resistance was maintained up to eight months without further exposure to spinosad. In the absence of any immigration of susceptible genes into the population, resistance was stable. In the case of the population with different initial frequency of resistant thrips, spinosad resistance declined significantly two months later in the absence of selection pressure. With successive generations, these strains did not change significantly in sensitivity. Spinosad resistance in F. occidentalis declined significantly in the absence of selection pressure and the presence of susceptible WFT. These results suggest that spinosad resistance probably is unstable under field conditions, primarily due to the immigration of susceptible WFT. Factors influencing stability or reversion of spinosad resistance are discussed.

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