In 1982 and 1983, effects of soybean row spacing and irrigation on weed resurgence following postemergence herbicide applications were evaluated. Also, ‘Forrest’ and ‘Ransom’ cultivar effects and early and late planting date influences on weed resurgence were evaluated in 1982 and 1983, respectively. In both years, as row spacing increased, weed resurgence increased. Photosynthetically active radiation measurements indicated the amount of weed resurgence coincided closely with the differing amounts of light penetrating to the soil surface. Irrigation, planting date, and cultivars showed no significant effect on weed resurgence. In 1982, a significant cultivar by row spacing interaction was obtained. In 1983, the late planting date showed a trend for less weed resurgence under irrigated conditions, although the difference was not significant. Soybean canopy measurements indicated development was greater under irrigation.

Field studies were conducted in 1996 and 1997 to determine postemergence control of purple (Cyperus rotundus) and yellow nutsedge (Cyperus esculentus) by single and sequential applications of bentazon, halosulfuron, and sulfentrazone; sequential applications of MSMA; and single applications of imazaquin and imazaquin plus MSMA. Sequential applications of halosulfuron at 70 g ai/ha controlled purple nutsedge more effectively at 10 wk after initial application (WAI) than all other herbicides. Single applications of imazaquin (0.56 kg ai/ha) or imazaquin plus monosodium salt of methylarsonic acid (MSMA, 2.24 kg ai/ha) controlled purple nutsedge adequately 6 WAI (78 and 90%, respectively) but not 18 WAI. Single applications of either halosulfuron (70 g/ha) or imazaquin plus MSMA or sequential applications of either bentazon (1.12 kg ai/ha), MSMA (2.8 kg/ha), or halosulfuron controlled yellow nutsedge greater than 80% by the end of the season in 1996 when nutsedge was in bermudagrass (Cynodon dactylon L.). However, in absence of bermudagrass in 1997, only sulfentrazone or the halosulfuron sequential treatments controlled yellow nutsedge 13 WAI. In 1996, single and sequential applications of halosulfuron reduced viability of purple nutsedge tubers to 33 and 30%, respectively, compared to 84% in the nontreated control. However, herbicide treatments did not reduce tuber viability in 1997. Sulfentrazone (0.28 kg ai/ha) plus MSMA (2.24 kg/ha) and sequential MSMA applications reduced viability of yellow nutsedge tubers to 6 and 31%, respectively, in 1997.

maximum growth inhibition at 2 to 5 wk after PGR applications, along with improvements in turfgrass qual-Research on the gibberellic acid (GA)-inhibiting plant-growth regity. Existing concerns in the golf course industry with ulator (PGR) trinexapac-ethyl (TE) regarding seasonal effects of single vs. multiple applications of this product on turfgrass quality and PGR applications in bermudagrass include turfgrass distissue production has not been reported. Research was conducted at coloration 1 to 2 wk after application and PIGE. Discol-North Carolina State University on 'Tifway' bermudagrass [Cynodon oration has been observed with applications of TE but dactylon (L.) Pers. ϫ Cynodon transvaalensis (Burtt-Davy)] to commay be counteracted by tank mixing TE with an Fe pare effects of different seasonal application patterns of TE. Applicasource (Johnson, 1997; Wiecko, 1997). The literature tions of TE were made to fully established Tifway bermudagrass at has not reported on either PIGE or how it may be either 0.107 or 0.071 kg a.i. ha Ϫ1 . Seasonal application patterns inaffected by the seasonal impact of multiple PGR applicluded an initial application, followed by zero, one, or two sequential cations. applications at 4-wk intervals. Plots were rated weekly for turfgrass Known warm-season turfgrass growth responses to quality and clippings were collected weekly for evaluation of tissue decreasing temperatures and reduced light levels in the production. Results demonstrated that one application of TE provided temporary growth inhibition of Tifway bermudagrass. This effect, as fall include cessation of new growth and net loss of expected, disappeared 4 wk after initial treatment (WAIT). Post-chlorophyll from leaf tissues. Research has been coninhibition growth enhancement (PIGE) was observed from 6 to 10 ducted to investigate how these effects may be delayed WAIT in areas treated with a single application of TE at 0.071 kg or counteracted, presumably to artificially extend the a.i. ha Ϫ1 . However, total seasonal tissue production following a single perceived growth period of these species. Exogenous application of TE was equal to untreated areas, suggesting limited additions of growth-regulating substances such as either overall effects of PIGE. Conversely, one or two sequential applicathe fungicide carboxin or the hormone GA have aided tions of TE provided prolonged growth inhibition; total seasonal tissue in the delay of bermudagrass dormancy symptoms (Diproduction was reduced by up to 40%. Overall quality of Tifway Paola et al., 1981; Dudeck and Peacock, 1985; Karnok bermudagrass was enhanced by multiple TE applications and per-

Turfgrass managers in the southeastern United States often overseed ‘Tifway’ bermudagrass [Cynodon transvaalensis Burtt‐Davey × C. dactylon (L.) Pers.] with perennial ryegrass (Lolium perenne L.) to provide a dense green turf during winter months. Although overseeding provides benefits, the spring transition from perennial ryegrass to bermudagrass can be troublesome and inconsistent. Perennial ryegrass may survive longer into the spring than is desired due to cool, wet conditions. The following experiment evaluated cultural methods for removal of perennial ryegrass from overseeded bermudagrass in the spring and early summer. The experiment was conducted at the North Carolina State University Turfgrass Field Center in Raleigh in the 1995 to 1996 and 1996 to 1997 growing seasons. Monocultures of ‘Gator’ and ‘Derby Supreme’ perennial ryegrass were overseeded into an established Tifway bermudagrass turf managed at golf course fairway conditions. It was hypothesized that various cultural treatments in the spring and summer could promote bermudagrass and/or discourage perennial ryegrass, and that the perennial ryegrass transition would differ depending on heat tolerance of the selected overseeding monocultures. The cultural treatments were biweekly vertical mowing, scalping, core cultivation, and vertical mowing/scalping, or two application timings of NH4NO3 Chemical removal of perennial ryegrass using pronamide [3,5‐dichloro‐N‐(1,1‐dimethyl‐2‐propynyl)benzamide] was included as a check treatment because it is commonly used to promote transition. Bermudagrass shoot density was consistently higher in nonoverseeded plots, illustrating perennial ryegrass competition. Cultural treatments affected perennial ryegrass cover during the spring and early summer but did not hasten its ultimate disappearance. Early or late applied NH4NO3 enhanced bermudagrass shoot density in both years. In contrast, plots receiving core cultivation had lower bermudagrass shoot density at the end of the transition period than the nontreated plots. Pronamide did hasten transition through 7 and 13 wk after initial treatment for 1996 and 1997, respectively. Regression analysis between natural perennial ryegrass disappearance over both years and air temperature or relative humidity indicates a significant association. This implies that cultural treatments alone may not consistently enhance natural transition of perennial ryegrass to bermudagrass.

The sedge genus Kyllinga consists of 40 to 45 species distributed in tropical, subtropical, and warm temperate regions around the world (KUkenthal 1936; Tucker 1987). This genus of low rhizomatous perennials or cespitose annuals is classified in the large cosmopolitan family Cyperaceae. Many Kyllinga species are considered weedy (Holm et al. 1979; Tucker 1987), while Kyllinga nervosa Steudel is considered an important forage plant in Africa (McNaughton 1985).