Control of perennated bermudagrass (Cynodon dactylon) and johnsongrass (Sorghum halepense) in sugarcane (Saccharum spp. hybrids)

In two separate field experiments conducted over time, at-planting preemergence (PRE) applications of sulfometuron at 110 to 150 g ai/ha followed by March applications of sulfometuron at 30 g/ha or metribuzin at 2,580 g ailha at the start of the initial (plant cane) growing season controlled more bermudagrass and johnsongrass emerging in sugarcane from rhizome and stolon pieces than standard at-planting followed by March applications of atrazine at 2,240 g ai/ha (no control), metribuzin at 2,580 g ai/ha, or pendimethalin at 2,240 g ai/ha. Treatments containing at- planting applications of imazapyr at 280 g ailha or thiazopyr at 560 g ai/ha did not provide levels of control similar to sulfometuron. Crop injury in excess of 10% occurred only when imazapyr at 280 g/ha (18 to 42%) or sulfometuron at 30 g/ha (11 to 32%) was applied in March to emerging sugarcane. Sugarcane stalk numbers, stalk heights, and ultimately cane and sugar yields were in- creased when compared to the standards with all sulfometuron treatments and when thiazopyr was applied at planting and again in March. Nomenclature: Atrazine, 6-chloro-N-ethyl-N'-(1-methylethyl)- 1,3,5-triazine-2,4-diamine; imazapyr, ( + )-2-(4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo- 1H-imidazol-2-yl)-3-pyridinecarboxylic acid; metribuzin, 4-amino-6-(1,1 -dimethylethyl)-3-(methylthio)- 1,2,4-triazin-5(4H)-one; pendimethalin, N- (1 -ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine; sulfometuron, 2-(((((4,6-dimethyl-2-pyrimidi- nyl)amino)carbonyl)amino)sulfonyl)benzoic acid; thiazopyr, methyl 2-(difluoromethyl)-5-(4,5-dihy- dro-2-thiazolyl)-4-(2-methylpropyl)-6-(trifluoromethyl)-3-pyridinecarboxylate; bermudagrass, Cyno- don dactylon (L.) Pers. #3 CYNDA; johnsongrass, Sorghum halepense (L.) Pers. # SORHA; sugar- cane, a complex hybrid of Saccharum spp. 'LCP 82-89.'