Date of Award

8-2014

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Plant and Environmental Science

Advisor

Dr. L.B. McCarty

Committee Member

Dr. Fred Yelverton

Committee Member

Dr. Scott McElroy

Committee Member

Dr. William Bridges

Abstract

Doveweed (Murdannia nudiflora [L.] Brenan) is a summer annual in the Southeastern United States with an expanding geographic range. The light green color and texture of doveweed is problematic for turfgrass managers as it contrasts with the color and texture of desirable turfgrasses. Limited research is available concerning the biology, ecology, and herbicide control options for doveweed. Therefore, experiments were conducted to improve the understanding of how environmental conditions effect doveweed germination, how cultural practices and environmental resource availability effect doveweed growth and development, to identify pre- and postemergence herbicides with efficacy for doveweed control, and to improve the understanding of why poor control is observed with postemergence herbicides. Doveweed germination was affected by scarification, osmotic potential and salt concentration. Mechanical abrasion of the seed coat increased germination to 84% compared to 18% in non-scarified seed. Germination was similar between osmotic potentials of 0 and -0.4 MPa and was reduced ~50% in a -0.8 MPa solution, suggesting doveweed favors a moist environment for germination. Germination was similar between NaCl concentrations of 0 and 40 mM, and reduced ~50% in a 160 mM NaCl solution, suggesting infestations can occur in moderately saline soils. Germination was not affected by nitrate concentration or pH. Doveweed spread of established plants was between 30 and 46% less in response to low mowing after one study year; however, differences in doveweed spread were not detected after year two. The lack of mowing height effect was attributed to recruitment of doveweed seedlings from seeds produced at the end of year one. This result suggests doveweed infestations can rapidly increase in severity if left unchecked. When grown in competition with `Tifway' bermudagrass (Cynodon dactylon [L.] Pers × C. transvaalensis Burtt-Davy), doveweed coverage per plant was ~38% less when mown at 1.32 cm compared to mowing at 2.65 cm. In the same study, increasing nitrogen rate from 24.5 to 49 kg N ha-1 increased doveweed spread per plant 75%. In response to a reduced light environment (RLE), shoot production did not increase on a weight basis; however, an etiolation response was detected as internode length increased 28% in plants grown in a 30% RLE and 39% in a 50 and 70% RLE. Root production on a weight basis was between 46 and 59% less in all RLE treatments compared to full sunlight treatments. Doveweed shoot growth was significantly greater in plants maintained above 50% field capacity (FC) and plants maintained at ≥75% FC produced more root biomass than 50, 25, and 12.5% FC treatments, further suggesting doveweed suggests a moist environment for growth and development. Sequential applications of pre- and postemergence herbicides improved doveweed control compared to single applications. Indaziflam, dimethenamid-p, and oxadiazon applied at 0.054, 1.68, and 3.36 kg ai ha-1, respectively, provided ~12, 6, and 6 wk of doveweed control, respectively, when applied on May 1 in Augusta, GA. Postemergence control was greatest following sequential application of sulfentrazone + metsulfuron at 0.30 kg ai ha-1, thiencarbazone + iodosulfuron + dicamba at 0.176 kg ai ha-1, 2,4-D + MCPP + dicamba + carfentrazone at 0.123 kg ai ha-1, or thiencarbazone + foramsulfuron + halosulfuron at 0.136 kg ai ha-1 21 days apart.

Included in

Plant Biology Commons

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