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Effects of Rainfall on Foliar Herbicides Applied to Seedling Johnsongrass (Sorghum halepense)

Published online by Cambridge University Press:  12 June 2017

Charles T. Bryson*
Affiliation:
U.S. Dep. Agric., Agric. Res. Serv., South. Weed Sci. Lab., P.O. Box 225, Stoneville, MS 38776

Abstract

The effects of rainfall on the efficacy of 11 foliar-applied herbicides were evaluated for their control of seedling johnsongrass [Sorghum halepense (L.) Pers. # SORHA] in greenhouse experiments during 1984 and 1985 at Stoneville, MS. Time intervals between herbicide application and rainfall (at 1.27 cm in 10 ± 0.5 min) ranged from 5 to 60 and 30 to 240 min depending on herbicide classification. In general, the phosphonic acid herbicides glyphosate [N-(phosphonomethyl)glycine] and SC-0224 (trimethylsulfonium carboxymethylaminomethylphosphonate) at 0.99 kg ai/ha required rain-free periods ≥240 min to control seedling johnsongrass effectively. The selective postemergence grass herbicides generally required ≥60 min to control seedling johnsongrass effectively when control without rainfall was ≥85%. Among the selective herbicides tested, haloxyfop {2-[4-[[3-chloro-5-(trifluoromethyl)-2-pyridinyl]oxy] phenoxy] propanoic acid} and DPX-Y6202 {ethyl[2-[4-(6-chloro-2-quinoxalinyl)oxy] phenoxy] propionic acid} at 0.06 kg ae/ha required the shortest time between herbicide application and rainfall to be effective. As herbicide rates were reduced, the effects of rainfall increased.

Type
Research
Copyright
Copyright © 1988 by the Weed Science Society of America 

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References

3 Letters following this symbol are a WSSA-approved computer code from Composite List of Weeds, Weed Sci. 32, Suppl. 2. Available from WSSA, 309 W. Clark St., Champaign, IL 61820. Google Scholar