Possible explanations of synergism in fungicide mixtures against <i>Phytophthom infestans</i>

Samoucha, Y.; Gisi, U.

doi:10.1111/j.1744-7348.1987.tb03260.x

Cited by 26 publications

(7 citation statements)

References 16 publications

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“…The first theory states that one fumigant may cause changes in cell wall permeability that, in turn, increases the uptake or decreases the efflux of a second fumigant from the cell 32. Another theory proposes that exposure of an organism to one fumigant may alter cell processes to an extent that exposure to a second compound is more deleterious than would normally be expected 33. A better understanding of the mechanisms of action of individual fumigants is necessary before a mechanism for synergism can be developed.…”

Section: Resultsmentioning

confidence: 99%

Fumigant combinations for Cyperus esculentum L control

Hutchinson

McGiffen

Sims

et al. 2003

Pest Management Science

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The phase-out of methyl bromide as a soil fumigant has stimulated research into the use of other soil fumigants for weed control. Methyl bromide, methyl iodide, propargyl bromide, 1,3-dichloropropene (1,3-D) and metam-sodium were tested alone and in combination with chloropicrin in laboratory experiments to determine their efficacy against Cyperus esculentus L (yellow nutsedge) tubers. Propargyl bromide and metam-sodium were the most efficacious fumigants tested, with EC50 values of 3.7 and 6.5 microM, respectively. The relative potencies of methyl iodide and chloropicrin were not significantly different but were 2.6 and 2.9 times more potent than methyl bromide, respectively. The EC50 values for all fumigants other than 1,3-D were significantly lower than that of methyl bromide. Combining each fumigant with 17% chloropicrin resulted in a synergistic interaction. The greatest increase in potency between the expected result and the actual result was a relative potency of 3.8 with the methyl bromide/chloropicrin combination. The smallest increase in efficacy was with propargyl bromide and chloropicrin, with a relative potency of 1.5. There was no significant difference between the EC50 values of methyl bromide/chloropicrin and methyl iodide/chloropicrin combinations. Combining 1,3-D with 17% chloropicrin resulted in an EC50 value for C. esculentus control similar to that of methyl iodide applied alone.

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Section: Resultsmentioning

confidence: 99%

Fumigant combinations for Cyperus esculentum L control

Hutchinson

McGiffen

Sims

et al. 2003

Pest Management Science

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“…All pesticides involved achieve an u max of 100%. For the pairs of atrazine/alachlor [ 12 ] (herbicides), aldrin/dieldrin [ 35 ] (insecticides), and oxadixyl/mancozeb [ 36 ] (fungicides) the root mean square errors of prediction are shown in Table 2 . The mixtures are equally well described by using variable slopes or slopes of 1.…”

Section: Discussionmentioning

confidence: 99%

Theory of synergistic effects: Hill-type response surfaces as ‘null-interaction’ models for mixtures

Schindler

2017

Theor Biol Med Model

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Background: The classification of effects caused by mixtures of agents as synergistic, antagonistic or additive depends critically on the reference model of 'null interaction'. Two main approaches are currently in use, the Additive Dose (ADM) or concentration addition (CA) and the Multiplicative Survival (MSM) or independent action (IA) models. We compare several response surface models to a newly developed Hill response surface, obtained by solving a logistic partial differential equation (PDE). Assuming that a mixture of chemicals with individual Hill-type dose-response curves can be described by an n-dimensional logistic function, Hill's differential equation for pure agents is replaced by a PDE for mixtures whose solution provides Hill surfaces as 'null-interaction' models and relies neither on Bliss independence or Loewe additivity nor uses Chou's unified general theory. Methods: An n-dimensional logistic PDE decribing the Hill-type response of n-component mixtures is solved. Appropriate boundary conditions ensure the correct asymptotic behaviour. Mathematica 11 (Wolfram, Mathematica Version 11.0, 2016) is used for the mathematics and graphics presented in this article. Results: The Hill response surface ansatz can be applied to mixtures of compounds with arbitrary Hill parameters. Restrictions which are required when deriving analytical expressions for response surfaces from other principles, are unnecessary. Many approaches based on Loewe additivity turn out be special cases of the Hill approach whose increased flexibility permits a better description of 'null-effect' responses. Missing sham-compliance of Bliss IA, known as Colby's model in agrochemistry, leads to incompatibility with the Hill surface ansatz. Examples of binary and ternary mixtures illustrate the differences between the approaches. For Hill-slopes close to one and doses below the half-maximum effect doses MSM (Colby, Bliss, Finney, Abbott) predicts synergistic effects where the Hill model indicates 'null-interaction'. These differences increase considerably with increasing steepness of the individual dose-response curves. Conclusion: The Hill response surface ansatz contains the Loewe additivity concept as a special case and is incompatible with Bliss independent action. Hence, when synergistic effects are claimed, those dose combinations deserve special attention where the differences between independent action approaches and Hill estimations are large.

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“…One mechanism suggested is that one fungicide causes changes in cell‐wall permeability that increases the uptake or decreases the efflux of a second fungicide from the cell 27. Another suggested mechanism is that sub‐lethal exposure of fungi to one fungicide may alter cell processes to such an extent that exposure to a second fungicide is more deleterious than would normally be expected 28. Further understanding of the activity of methyl bromide, methyl iodide and chloropicrin is necessary before a mechanism of synergism can be deduced.…”

Section: Discussionmentioning

confidence: 99%

Efficacy of methyl iodide and synergy with chloropicrin for control of fungi

et al. 2000

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Efficacy of soil fumigation with methyl bromide and methyl iodide against Botrytis cinerea, Colletotrichum gloeosporioides, Fusarium oxysporum, Gliocladium virens, Phytophthora citricola, Phytophthora citrophthora, Pythium ultimum, Rhizoctonia solani and Verticillium dahliae was determined in laboratory experiments in closed fumigation chambers. Pythium ultimum was the most sensitive fungal species with EC50 values for methyl bromide and methyl iodide of 15.5 and 8.6 µM, respectively. R solani was the least sensitive with EC50 values of 253.4 and 161.4 µM for methyl bromide and methyl iodide, respectively. Relative potency ([methyl bromide]/[methyl iodide]) values ranged from 5.2 for P citricola to 1.5 for F oxysporum. Methyl iodide was 2.7 more efficacious than methyl bromide averaged over all fungal species. Methyl bromide/chloropicrin and methyl iodide/chloropicrin applied jointly were 2.2 and 2.8 times more efficacious, respectively, against F oxysporum than when the compounds were applied singly. Combining methyl bromide and methyl iodide with chloropicrin resulted in a significant synergistic increase in activity against F oxysporum. © 2000 Society of Chemical Industry

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Possible explanations of synergism in fungicide mixtures against Phytophthom infestans

Cited by 26 publications

References 16 publications

Fumigant combinations for Cyperus esculentum L control

Fumigant combinations for Cyperus esculentum L control

Theory of synergistic effects: Hill-type response surfaces as ‘null-interaction’ models for mixtures

Efficacy of methyl iodide and synergy with chloropicrin for control of fungi

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