Tropical signalgrass is one of the dominant weeds in the Florida turfgrass industry and is potentially troublesome for the southeastern turfgrass industry. Tropical signalgrass is especially problematic for St. Augustinegrass sod producers because of lack of control options. The objectives of our research were to determine the effect of light, pH, temperature, water potential, and planting depth on tropical signalgrass germination and emergence. Tropical signalgrass germination does not require light and is optimum at pH 5 to 6, temperature 25 C, and water potentials greater than − 0.4 MPa. Tropical signalgrass shoots emerged from depths of 0 to 7 cm, with maximum germination when placed on the soil surface. Tropical signalgrass seedlings emerged in the field during the second week of March in Ft. Lonesome, FL. Weekly mean soil and ambient air temperatures at the time of emergence were 20 C. Tropical signalgrass emergence was first observed at 118 and 73 growing degree-days (GDD) (13 C base temperature), with a peak emergence period at 222 and 156 GDD for 2001 and 2002, respectively.

Water shortages have become more chronic as periodic droughts prolong and water demand for urban and agricultural use increases. Plant drought responses involve coordinated mechanisms in both above‐ and below‐ground systems, yet most studies lack comparisons of root and canopy responses under water scarcity and recovery. This is particularly true of research focused on warm‐season turfgrasses in sandy soils with extremely low water holding capacity. To address the lack of examination of coordinated stress and recovery responses, this study compared the above‐ and below‐ground plant responses during a dry‐down period of 21 days and recovery among four warm‐season turfgrass species in the field. Canopy drought responses and recovery were quantified using digital image analysis. In situ root images were captured using a minirhizotron camera system. Common bermudagrass [Cynodon dactylon (L.) Pers.] endured the entire drought period without losing 50% green cover while other species lost 50% green cover in 11–34 days predicted from the regression. The interspecific differences in drought resistance were mainly due to root characteristics. Other drought mechanisms appear to be responsible for differences identified in drought resistance between “Zeon” and “Taccoa Green” manilagrass [Zoysia matrella (L.) Merr.]. Recovery was delayed for up to 2 weeks in the second year, warranting further evaluation for turfgrass persistence under long‐term drought. Three‐week drought posed no threat to the survival of zoysiagrass. Species and genotypic variations were found in achieving full post‐recovery, which can be used to develop water conservation strategies and to adjust consumer expectations.

Degree-day modeling applications in turfgrass management have recently seen increased interest. The predictive capacity of any degreeday model is dependent on an accurate determination of the basal growth temperatures for the species under consideration. The objective of this study was to determine basal growth temperatures and growth rate constants for eight warm season turfgrasses (five species). Sprigs from bermudagrass [Cynodon dactylon (L.) Pers. cv. Arizona Common and C. dactylon Ic C. transvaalensis Burtt Davey cv. Midiron], buffaiograss [Buchlo# dactyloides (Nutt.) Engeim. cv. Kansas Common and Texoka], zoysiagrass (Zoysia japonica Steudel cv. Meyer), St. Augustinegrass [Stenotaphrum secundatum (Walter) Kuntze cv. Raleigh and Floratam], and centipedegrass [Ereraochloa ophiuroides (Munro) Hackel, cv. Common] were grown at temperatures ranging from 5 to 30°C in a controlled environment chamber under 14-h photoperiods. Chamber temperature was decreased in a step-wise fashion to the next temperature after two leaves were fully expanded. Leaf growth rates at each temperature were calculated and expressed as millimeters per day. Base temperature and growth rate constants for each turfgrass were calculated with segmented nonlinear regression analysis. Base temperatures for the eight tested cnltivars ranged from 0 to 13°C. Interspecific and intraspecific differences for basal growth temperature were found, indicating that degree-day model application accuracy is dependent on proper determination of target species and cultivar basal growth temperature.

Potassium azide (PA) (112 kg/ha), oxadiazon + 1,3-dichloropropene (1,3-D) (168 kg/ha + 140 L/ha), dazomet (392 kg/ha), dazomet + chloropicrin (392 + 168 kg/ha), dazomet + 1,3-D (392 kg/ha + 140 L/ha), iodomethane (IM) (336 kg/ha), metam-sodium (MS) (748 L/ha), MS + chloropicrin (748 L/ha + 168 kg/ha), and MS + 1,3-D (748 + 140 L/ha) were evaluated at Jay and Arcadia, FL, in 1998 and 1999 as alternatives to methyl bromide (MeBr) fumigation for the management of common turfgrass weeds. Potassium azide was as effective as MeBr in controlling ‘Coastal’ bermudagrass, yellow and purple nutsedges, alexandergrass, broadleaf signalgrass, tall and sharppod morningglories, and various winter annual broadleaf weeds, but it failed to provide acceptable control of redroot pigweed. 1,3-Dichloropropene + oxadiazon did not control yellow nutsedge, purple nutsedge, or Coastal bermudagrass. Similarly, this combination treatment failed to control carpetweed but did provide 83% control of the winter annual weed species, 71% control of alexandergrass and broadleaf signalgrass, and ≥ 80% control of tall morningglory, sharppod morningglory, and redroot pigweed. Dazomet + combination treatments provided control of Coastal bermudagrass at Jay; however, control of common bermudagrass, alexandergrass, and broadleaf signalgrass was not acceptable at Arcadia. Sedge species control with dazomet + combinations was poor (< 63%) at both sites. Iodomethane, a treatment not yet registered by the U.S. Environmental Protection Agency (EPA), controlled weedy grass species, sedge species, and broadleaf weeds present at the two locations under different environmental conditions. Metam-sodium alone and MS + chloropicrin, tarped and untarped, and MS + 1,3-D provided acceptable weed control; however, MS + chloropicrin covered with a plastic tarp for 48 h was the best MS treatment. Metam-sodium + chloropicrin, with plastic tarp, controlled weedy grass and broadleaf species equal to MeBr; however, unacceptable sedge species control at Jay and Arcadia was 56 and 79%, respectively. Metam-sodium applied alone failed to control redroot pigweed; however, MS + combinations provided control. These studies confirm that no EPA-registered fumigant alternative to MeBr, applied alone or in combination for preplant turf soil fumigation, exists. Consequently, until such time that an effective alternative is identified, turf managers will be forced to forego fumigation, or they will have to choose a less-effective alternative and accept the consequences of contamination.