Date of Award

1990

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Plant, Environmental Management and Soil Sciences

First Advisor

James L. Griffin

Second Advisor

Gerrard T. Berggren

Abstract

The spread of itchgrass (Rottboellia cochinchinensis (Lour.) Clayton) throughout the sugarcane (Saccharum interspecific hybrids) area is of growing concern to producers in Louisiana. At Maringouin and Thilbodaux, LA, season-long itchgrass interference reduced sugarcane stalk populations, cane yields, and sugar yields 34, 42, and 43%, respectively, compared to no itchgrass interference. Stalk populations and cane and sugar yields were comparable for early-season (from spring until layby on June 12) and season-long itchgrass interference with late-season (from layby on June 12 until harvest) being similar to no itchgrass interference. Good to excellent early-season itchgrass control was obtained with pendimethalin at 2.2 and 3.4 kg/ha plus atrazine, prodiamine at 1.7 to 2.8 kg/ha, clomazone at 1.1 to 2.2 kg/ha, and fomesafen at 0.8 to 1.1 kg/ha at two locations. Late-season itchgrass populations were reduced at least 80%, at the Loreauville site. BAS 514 at 0.3 to 1.1 kg/ha, metribuzin, and atrazine provided poor control. Only clomazone injured sugarcane, but the bleaching of foliage was short-lived. In a field study, which supported the results observed in the greenhouse, a postemergence application of asulam at 3.7 kg/ha reduced dry biomass 89%. Nicosulfuron at 9 to 35 g/ha reduce itchgrass dry biomass 77 to 89%, but control with primasulfuron methyl at 34 and 67 g/ha and KIH 2665 at 112 g/ha was poor. Over-the-top application of nicosulfuron at 18 to 67 g/ha at Maringouin and Thibodaux, LA, reduced sugarcane stalk populations at least 91% compared to the untreated check. Stalk populations were reduced 93% at Maringouin with primasulfuron methyl at 34 g/ha but were unaffected by KIH 2665 at either location. Postemergence-directed application of nicosulfuron also caused significant sugarcane injury. Paraquat at 560 g/ha and ametryn at 2.7 kg/ha applied post emergence reduced itchgrass infestation levels. Although injury was observed with paraquat, there was no reduction in stalk height, stalk number, or sugar yield.

Pages

66

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