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Effect of Cry IC toxin from Bacillus thuringiensis on larval feeding behavior of Spodoptera exigua
Author(s) -
Berdegué Mariano,
Trumble John T.,
Moar William J.
Publication year - 1996
Publication title -
entomologia experimentalis et applicata
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.765
H-Index - 83
eISSN - 1570-7458
pISSN - 0013-8703
DOI - 10.1111/j.1570-7458.1996.tb00951.x
Subject(s) - exigua , instar , biology , spodoptera , bacillus thuringiensis , noctuidae , larva , toxin , zoology , microbiology and biotechnology , pest analysis , lepidoptera genitalia , bacillales , toxicology , botany , biochemistry , bacteria , genetics , gene , recombinant dna , bacillus subtilis
The lack of data on the effect of Bacillus thuringiensis (B.t.) toxins on larval feeding behavior of the pest Spodoptera exigua (Hübner) (Noctuidae: Amphypyrini) prompted us to investigate the effect of three delivery systems of Cry IC, a commercial formulation, inclusion bodies, and the activated Cry IC toxin. The commercial formulation was the least and Cry IC toxin the most lethal form to neonates of susceptible colonies. All but two of the treatments in choice tests with neonates and third instars showed significant avoidance of B.t. treated diet, with greater proportion of larvae from susceptible (UCR‐S and AUBURN‐S) and resistant (AUBURN‐R) colonies on untreated diet than on diet treated with any of the Cry IC forms and concentrations tested. Furthermore, third instars consumed significantly more control than treated diet for all Cry IC forms, colonies and concentrations. The avoidance of Cry IC toxin by neonates and third instars strongly suggests that Cry IC, which also is present in the commercial formulation and in the inclusion bodies, is responsible for eliciting avoidance behavior by S. exigua larvae. Behavioral observations of third instars in a no‐choice test on either treated or control diet indicated that questing behavior in susceptible larvae appears to be positively related with presence of Cry IC toxin in the diet. Furthermore, resistant third instars were on the whole more active than susceptible thirds on both treated and control diet. Resistant thirds raised on Cry IC treated diet (AUBURN‐RC) spent more time eating treated diet than resistant larvae raised on control diet (AUBURN‐R), suggesting that diet conditioning plays an important role on feeding behavior of S. exigua . The implications of these results are discussed.