Binary mixtures of feeding deterrents mitigate the decrease in feeding
deterrent response to antifeedants following prolonged exposure in the
cabbage looper, <Emphasis Type="Italic">Trichoplusia ni</Emphasis> (Lepidoptera: Noctuidae) |
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Authors: | Yasmin?Akhtar Email author" target="_blank">Murray?B?IsmanEmail author |
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Institution: | (1) Faculty of Agricultural Sciences, University of British Columbia, V6T 1Z4 Vancouver, BC, Canada |
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Abstract: | Summary. The effect of rearing larvae of Trichoplusia ni on
individual feeding deterrents or on binary mixtures of deterrents
on their subsequent gustatory sensitivity was measured
in paired choice leaf disc bioassays. Our working hypothesis
was that mixtures of antifeedants (pure allelochemicals)
would mitigate decreased feeding deterrent response following
prolonged exposure in this generalist herbivore. Neonate
larvae were reared on cabbage leaves treated with individual
feeding deterrents (digitoxin, thymol, toosendanin or xanthotoxin),
or with binary mixtures of these until the third instar.
Feeding deterrent responses to each antifeedant or mixture
was then determined in a leaf disc choice bioassay. All of the
mixtures produced additive deterrence when presented to
naïve larvae. Larvae reared on individual antifeedants
showed a significantly decreased feeding deterrent response
(except to digitoxin), whereas larvae reared on binary mixtures
of antifeedants did not show a decreased feeding deterrent
response to any of them. Such mixtures were synergistic
in terms of their feeding deterrence to experienced larvae.
Our experiment supports the hypothesis (Jermy 1986) that
mixtures of deterrents can prevent decreased feeding deterrent
response following prolonged exposure, and provides one
explanation for the multiplicity of chemical defenses found
in many plants. |
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Keywords: | Antifeedants Trichoplusia ni digitoxin thymol xanthotoxin toosendanin binary mixtures feeding deterrence |
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