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Journal ArticleDOI

A method of computing the effectiveness of an insecticide

01 Apr 1925-Journal of Economic Entomology (Oxford Academic)-Vol. 18, Iss: 2, pp 265-267
TL;DR: In order to make experimental studies comparable and statistically meaningful, the article recommends the following formula: per cent control = 100(X - Y)/X, which eliminates errors due to deaths in the control sample which were not due to the insecticide.
Abstract: There are several statistical methods used in biology (entomology) for computing the effectiveness of an insecticide, based on relating the number of dead insects in the treated plat to the number of live ones in the untreated plat. In order to make experimental studies comparable and statistically meaningful, the article recommends the following formula: per cent control = 100(X - Y)/X, where X = % living in the untreated check sample and Y = % living in the treated sample. Calculation using this method eliminates errors due to deaths in the control sample which were not due to the insecticide. An example based on treatments of San Jose scale includes computation of probable errors for X and Y, and the significance of the difference between the two counts. Common biometric convention holds that when the difference between the results of two experiments is greater than three times its probable error, the results are significant and due to the treatment applied.
Citations
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Journal ArticleDOI
TL;DR: Data suggest the involvement of acetylcholinesterase in the coevolved insect response to terpenoids, as well as a range of functional groups, that were reversible competitive inhibitors apparently occupying at least the hydrophobic site of the enzyme's active center.
Abstract: The theory of plant-insect coevolution provides for diffuse coevolution and the expectation that plants evolve broad-spectrum chemical defenses with which some insects coevolve by detoxifying and using the compounds as host-location cues. Specific biochemical modes of action have been assigned to relatively few such defense chemicals and one major class, the terpenoids, is investigated here. Six terpenoids inhibited the enzyme acetylcholinesterase (derived from electric eel) and elicited the appropriate in vivo effects of insect paralysis and mortality. The diterpene gossypol was a reversible uncompetitive inhibitor. Five monoterpenes, representing a range of functional groups, were reversible competitive inhibitors apparently occupying at least the hydrophobic site of the enzyme's active center. Such data suggest the involvement of acetylcholinesterase in the coevolved insect response to terpenoids.

326 citations


Cites methods from "A method of computing the effective..."

  • ...Correction for control mortality was made using the Abbott formula (Abbott, 1925), PT = [(Po - Pc)/100 Pc] X 100, where PT is corrected percentage mortality, Po is observed mortality, and Pc is control mortality....

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Journal ArticleDOI
TL;DR: It is shown that cross-resistance exists between Cry3Bb1 maize and mCry3A maize and is associated with severe injury to Bt maize in farmers’ fields, illustrating the potential of insects to develop resistance rapidly when Bt crops do not achieve a high dose of Bt toxin.
Abstract: The widespread planting of crops genetically engineered to produce insecticidal toxins derived from the bacterium Bacillus thuringiensis (Bt) places intense selective pressure on pest populations to evolve resistance. Western corn rootworm is a key pest of maize, and in continuous maize fields it is often managed through planting of Bt maize. During 2009 and 2010, fields were identified in Iowa in which western corn rootworm imposed severe injury to maize producing Bt toxin Cry3Bb1. Subsequent bioassays revealed Cry3Bb1 resistance in these populations. Here, we report that, during 2011, injury to Bt maize in the field expanded to include mCry3A maize in addition to Cry3Bb1 maize and that laboratory analysis of western corn rootworm from these fields found resistance to Cry3Bb1 and mCry3A and cross-resistance between these toxins. Resistance to Bt maize has persisted in Iowa, with both the number of Bt fields identified with severe root injury and the ability western corn rootworm populations to survive on Cry3Bb1 maize increasing between 2009 and 2011. Additionally, Bt maize targeting western corn rootworm does not produce a high dose of Bt toxin, and the magnitude of resistance associated with feeding injury was less than that seen in a high-dose Bt crop. These first cases of resistance by western corn rootworm highlight the vulnerability of Bt maize to further evolution of resistance from this pest and, more broadly, point to the potential of insects to develop resistance rapidly when Bt crops do not achieve a high dose of Bt toxin.

323 citations


Cites methods from "A method of computing the effective..."

  • ...Abbott WS (1925) A method of computing the effectiveness of an insecticide....

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  • ...For every population within each year, corrected survival on Cry3Bb1 maize was calculated based on Abbott (41), as proportion survival on Cry3Bb1 maize divided by proportion survival on non-Bt maize....

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Journal ArticleDOI
TL;DR: Benzaldehyde and other natural volatiles could be a safer fumigant to control stored-grain insect pests than those currently used.

319 citations

Book ChapterDOI
01 Jan 1997
TL;DR: It is found that although most entomopathogenic Hyphomycetes will produce blastospores in submerged culture, specific parameters need to be evaluated and adjusted for every strain studied for optimum blastospore production.
Abstract: Publisher Summary This chapter discusses isolation, culture, and production of order Hyphomycetes. Hyphomycetes are filamentous fungi that reproduce by conidia generally formed aerially on conidiophores arising from the substrate. Most entomopathogenic Hyphomycetes are facultative pathogens and are relatively easily grown in pure culture on defined or semidefined media. Entomopathogenic Hyphomycetes may be harvested directly from insect cadavers on which the fungus has already sporulated. Another isolation method requires the homogenization of cadavers followed by dilution plating of the homogenate on an appropriate selective medium. Selective media are frequently used for the isolation of entomopathogenic Hyphomycetes. Inhibition of contaminant fungi is more problematic than bacteria, and fungal contaminants are invariably a problem when attempting to isolate entomopathogenic Hyphomycetes from soil. It is found that although most entomopathogenic Hyphomycetes will produce blastospores in submerged culture, specific parameters need to be evaluated and adjusted for every strain studied for optimum blastospore production. An approach for bioassay of entomopathogenic fungi against fourth instar nymphs of the silverleaf whitefly is also elaborated.

312 citations

Journal ArticleDOI
TL;DR: Flubendiamide is expected to be a suitable agent for controlling lepidopterous insects as part of the insect resistance management and the integrated pest management programs.
Abstract: Flubendiamide, N2-[1,1-dimethyl-2-(methylsulfonyl)ethyl]-3-iodo-N1-[2-methyl-4-[1,2,2,2-tetrafluoro-1-(trifluoromethyl)ethyl]phenyl]-1,2-benzenedicarboxamide, is a novel class of insecticide having a unique chemical structure. The uniqueness of the structure results from three parts with novel substituents; a heptafluoroisopropyl group in the anilide moiety, a sulfonylalkyl group in the aliphatic amide moiety, and an iodine atom at the 3-position of the phthalic acid moiety. The compound shows extremely strong insecticidal activity especially against lepidopterous pests including resistant strains. Flubendiamide would have a novel mode of action, because the insecticidal symptoms accompanied by a discriminative contraction of the larval body are distinguished from those of commercial insecticides. It is also very safe for non-target organisms. Flubendiamide is expected to be a suitable agent for controlling lepidopterous insects as part of the insect resistance management and the integrated pest management programs. © Pesticide Science Society of Japan

310 citations