Identifier

etd-06292016-132414

Degree

Master of Science (MS)

Department

Plant, Enviromental and Soil Sciences

Document Type

Thesis

Abstract

To provide for a weed-free seedbed, Louisiana crop producers typically apply a burndown herbicide four to six wk prior to seeding summer annual crops; however, these treatments often provide inadequate henbit (Lamium amplexicaule L.) control. Research was conducted in Louisiana to evaluate henbit emergence from north to south, compare growth of henbit accessions based on emergence date, and control with fall-applied residual herbicides. For the emergence study during the weeks of Oct 17 to Dec 12 at all locations in all years, soil temperatures at 2.5 cm averaged between 10 and 18.5 C. Henbit at densities of at least 50 m-2 emerged each week from approximately Oct 20 through Dec 20, for the three northern most sites which included the Northeast Research Station, a grower’s field in Concordia Parish, and the Dean Lee Research and Extension Center.. At all three northern most locations counts in excess of 1000 henbit m-2 were observed in November, indicating potential for high henbit density at these locations. Henbit emergence was more sporadic from 2012 through 2015 for the three northern locations, with densities not exceeding 40 henbit m-2 at the Dean Lee Research and Extension Center, although large single week increases in the number of henbit did occur between mid-October to mid-December at those locations. Regardless of year, densities at the Ben Hur Research Farm, the southern location, were less overall. Averaged across emergence date leaf area ratio (LAR) for September and October was 0.012 and 0.010 cm2 g-1, respectively, and although not significantly different was greater than henbit emerging in November. Specific leaf weight (SLW) for henbit emergence in November was 119.0 g cm-2, greater than September and October populations at 54 and 89 g cm-2, respectively. Additionally, relative growth rate (RGR) for September emerged henbit averaged across harvest intervals was 0.194 g g-1 d-1, and greater than for both October and November emerged henbit with 0.121 and 0.092 g g-1 d-1, respectively. Results suggest that September emerged henbit could be larger and more difficult to control than November emerged henbit. However, October populations had similar trends and were not different than September emerged henbit, conceding that any competitive advantage September may have over October is slight. For fall applied residual herbicides study variability in henbit control, across years was observed. Overall, application Nov 1 through Dec 1 provided more consistent henbit control compared with oxyfluorfen applications controlled henbit at least 76% 100 DAT regardless of herbicide date. For flumioxazin and rimsulfuron: thifensulfuron, greater than 70% henbit control 100 DAT was obtained only when applied Nov 1 through Dec 15.

Date

2016

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Griffin, James L.

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