From lethality to mortality: exploring the “grey area” of knockdown as an efficacy indicator of different insecticides against major storage insects using a lethality index

From lethality to mortality: exploring the “grey area” of knockdown as an efficacy indicator... In the present work, a lethality index was applied for the evaluation of three insecticides with different modes of action, i.e., thiamethoxam, chlorfenapyr and lambda-cyhalothrin, as surface treatment against adults of Sitophilus oryzae (L.), Oryzaephilus surinamensis (L.) and Tribolium confusum Jacquelin du Val, in laboratory bioassays. The insecticides were applied at their highest label dose, while insect knockdown and mortality were evaluated after 1, 3, 5 and 7 days of exposure to the treated surfaces according to the Standardized Lethality Index, by ranking each insect from “0” to “4,” with “0” corresponding to insects moving normally and “4” corresponding to dead individuals. After the end of the exposure, the surviving insects were transferred to clean, untreated dishes and delayed mortality was assessed after an additional period of 1, 3, 5 and 7 days. Based on the results, initial knockdown was high for S. oryzae after exposure to thiamethoxam and lambda-cyhalothrin even after 1 day of exposure, whereas for longer exposures high mortality levels were recorded. In contrast, in the case of chlorfenapyr knockdown was low after 1 day of exposure; however, high mortality levels were noted after 3 and 5 days of exposure. Similar results were noted for O. surinamensis, which was highly susceptible to all three insecticides tested. The most tolerant insect species to the tested insecticides was T. confusum, since a noticeable number of T. confusum adults were still active at the end of the exposure (7 days). Our results indicate that knockdown is most likely to lead to mortality than to recovery, but there were important differences among the three insecticides tested. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Pest Science Springer Journals

From lethality to mortality: exploring the “grey area” of knockdown as an efficacy indicator of different insecticides against major storage insects using a lethality index

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Publisher
Springer Journals
Copyright
Copyright © 2018 by Springer-Verlag GmbH Germany, part of Springer Nature
Subject
Life Sciences; Entomology; Agriculture; Plant Pathology; Ecology; Forestry; Plant Sciences
ISSN
1612-4758
eISSN
1612-4766
D.O.I.
10.1007/s10340-018-0983-z
Publisher site
See Article on Publisher Site

Abstract

In the present work, a lethality index was applied for the evaluation of three insecticides with different modes of action, i.e., thiamethoxam, chlorfenapyr and lambda-cyhalothrin, as surface treatment against adults of Sitophilus oryzae (L.), Oryzaephilus surinamensis (L.) and Tribolium confusum Jacquelin du Val, in laboratory bioassays. The insecticides were applied at their highest label dose, while insect knockdown and mortality were evaluated after 1, 3, 5 and 7 days of exposure to the treated surfaces according to the Standardized Lethality Index, by ranking each insect from “0” to “4,” with “0” corresponding to insects moving normally and “4” corresponding to dead individuals. After the end of the exposure, the surviving insects were transferred to clean, untreated dishes and delayed mortality was assessed after an additional period of 1, 3, 5 and 7 days. Based on the results, initial knockdown was high for S. oryzae after exposure to thiamethoxam and lambda-cyhalothrin even after 1 day of exposure, whereas for longer exposures high mortality levels were recorded. In contrast, in the case of chlorfenapyr knockdown was low after 1 day of exposure; however, high mortality levels were noted after 3 and 5 days of exposure. Similar results were noted for O. surinamensis, which was highly susceptible to all three insecticides tested. The most tolerant insect species to the tested insecticides was T. confusum, since a noticeable number of T. confusum adults were still active at the end of the exposure (7 days). Our results indicate that knockdown is most likely to lead to mortality than to recovery, but there were important differences among the three insecticides tested.

Journal

Journal of Pest ScienceSpringer Journals

Published: Jun 4, 2018

References

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