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The Relative Response of Two Foxtail (Setaria) Species to Diclofop

Published online by Cambridge University Press:  12 June 2017

Ian N. Morrison
Affiliation:
Univ. of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2
Denise C. Maurice
Affiliation:
Univ. of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2

Abstract

ED50 values (the dosage required to reduce the posttreatment gain in dry weight by 50%) for diclofop applied to green and yellow foxtail [Setaria viridis (L.) Beauv. ♯3 SETVI and S. lutescens (Weigel.) Hubb. ♯ SETLU] at the two- and four-leaf stages were calculated from linear regression equations derived by plotting the logarithm of the applied dosage against the relative growth reduction expressed as a probit value. At the two-leaf stage, green foxtail was more susceptible to the chemical than yellow foxtail but at the four-leaf stage there was no significant difference in response of the two species. At least part of the difference in sensitivity of the two species at the two-leaf stage could be accounted for by differences in spray retention, with green foxtail retaining 1.8 times (expressed as μL/cm2) or 3.5 times (expressed as μL/g dry weight) as much spray as yellow foxtail, despite the fact that yellow foxtail had a greater projected leaf area. At the four-leaf stage, the amount of spray retained by both species calculated on a per gram dry-weight basis was significantly less than at the two-leaf stage, accounting in part for the higher ED50 values obtained at the later growth stage. However, there appeared to be no direct relationship between the amount of spray retained and the comparative growth response of the two weeds at the later stage of application.

Type
Weed Biology and Ecology
Copyright
Copyright © 1984 by the Weed Science Society of America 

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References

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