Johnsongrass (Sorgbum halepense) Control with Herbicides in Oil Diluents

TLDR: In this article, the authors evaluated the effectiveness of different diluents and spray volumes for the control of rhizome johnsongrass using one to three types of ap-plicators from 1983 to 1985.

Abstract: Control of seedling and rhizome johnsongrass (Sorghum balepense (L.) Pers. #3 SORHA) with five herbi- cides was evaluated after postemergence application in various diluents and spray volumes using one to three types of ap- plicators from 1983 to 1985. The rate of each herbicide re- quired to control seedling johnsongrass using paraffinic oil as the diluent in applications with an external- or internal- mixing air-assist sprayer at a spray volume of 9.4 L/ha was one-half the rate required when water plus 1.25% (v/v) paraf- finic oil concentrate (POC) or water plus 1.25% (v/v) soybean oil concentrate (SOC) were the diluents in applications with a conventional sprayer equipped with fan jet spray nozzles at a spray volume of 187 L/ha. Rates were also reduced when once-refined soybean oil was the diluent at a spray volume of 9.4 L/ha, except for the ethyl ester of quizalofop {(?)-2- (4- ((6 - chloro- 2-quinoxalinyl)oxy) phenoxyl propanoic acid}. Sethoxydim {2- (1- (ethoxyimino)butyl) -5- (2- (ethylthio)pro- pyl) - 3-hydroxy- 2- cyclohexen- 1-one} was equally effective on seedling johnsongrass growing in soybeans (Glycine max (L.) Merr. 'DPL 105') when applied at 224 g ai/ha with an internal-mixing air-assist sprayer or a controlled-droplet applicator (CDA) at a spray volume of 9.4 L/ha and a con- ventional sprayer at a spray volume of 187 L/ha, regardless of diluent. Conventional application required the use of 1.25% (v/v) SOC or POC as part of the diluent to be effec- tive. For three of the five herbicides evaluated on rhizome johnsongrass, paraffinic oil at a spray volume of 9.4 L/ha was the only diluent that resulted in season-long control. Rhizome johnsongrass control with this diluent also re- sulted in significantly higher soybean yields than all other diluent- spray volume treatments. Additional index words. Haloxyfop, quizalofop, cloproxy- dim, fluazifop- P, sethoxydim, paraffinic oiL soybean oil, soybean oil concentrate, paraffinic oil concentrate, adjuvants, spray volume, spray equipment, SORHA.