Preemergence herbicides generally have a negative effect on hybrid bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy] establishment. However, little is known about the effect they have on root architecture and development. Research was conducted to determine the effects of commonly used preemergence herbicides on ‘Latitude 36’ hybrid bermudagrass root architecture and establishment. The experiment was conducted in a climate-controlled greenhouse maintained at 26 °C day/night temperature at Mississippi State University in Starkville, MS, from Apr. 2016 to June 2016 and repeated from July 2016 to Sept. 2016. Hybrid bermudagrass plugs (31.6 cm2) were planted in 126-cm2 pots (1120 cm3) and preemergence herbicide treatments were applied 1 d after planting at the recommended labeled rate for each herbicide. Preemergence herbicide treatments included atrazine, atrazine + S-metolachlor, dithiopyr, flumioxazin, indaziflam, liquid and granular applied oxadiazon, S-metolachlor, pendimethalin, prodiamine, and simazine. Treatments were arranged in a completely randomized design with four replications. Plugs treated with indaziflam and liquid applied oxadiazon failed to achieve 50% hybrid bermudagrass cover by the end of the experiment. Of the remaining herbicide treatments, all herbicides other than granular applied oxadiazon and atrazine increased the number of days required to reach 50% cover (Days50). In addition, all herbicide treatments reduced root mass when harvested 6 weeks after treatment (WAT) relative to the nontreated. By 10 WAT, all treatments reduced root mass in run 1, but during run 2, only prodiamine, pendimethalin, simazine, atrazine + S-metolachlor, liquid applied oxadiazon, and indaziflam reduced dry root mass compared with the nontreated. At 4 WAT, all treatments other than simazine and granular applied oxadiazon reduced root length when compared with the nontreated. By 10 WAT, only dithiopyr, S-metolachlor alone, and indaziflam reduced root length when compared with the nontreated. No differences were detected in the total amounts of nonstarch nonstructural carbohydrates (TNSC) within the roots in either run of the experiment. Results suggest that indaziflam, dithiopyr, and S-metolachlor are not safe on newly established hybrid bermudagrass and should be avoided during establishment. For all other treatments, hybrid bermudagrass roots were able to recover from initial herbicidal injury by 10 WAT; however, future research should evaluate tensile strength of treated sod.
Regalia®, a commercial extract of giant knotweed [Fallopia sachalinensis F. Schmidt (synonyms: Reynoutria sachalinensis (F. Schmidt) Nakai, Polygonum sachalinense F. Schmidt, Tiniaria sachalinesis (F. Schmidt) Janch.)], was evaluated for its potential to enhance drought tolerance of container-grown impatiens (Impatiens walleriana Hook. f. ‘Super Elfin XP White’). In two separate experiments, Regalia® was foliar-applied once a week for 4 weeks at four different rates (0, 5, 10, or 15 mL·L−1). In Expt. 1, Regalia® was applied to impatiens grown under three target substrate volumetric water contents (TVWCs): 85%, 55%, or 25%. In Expt. 2, Regalia® was applied to impatiens watered with 1, 3, or 6 days between waterings (DBW). In Expt. 1, root dry weight (RDW) of impatiens receiving applications of Regalia® at the 0.5× rate was greater compared with the 0.0× rate across all TVWCs. Additionally, soluble protein content was greater after Regalia® application at the 0.5×, 1.0×, or 1.5× rates compared with the 0.0× rate for plants grown at 55% TVWC. In Expt. 2, leaf greenness (SPAD) and leaf net photosynthetic rate (Pn) were greater with Regalia® applied at the 0.5× and 1.0× rates compared with the 0.0× rate, respectively. Soluble protein content was greater in impatiens treated with Regalia® at the 1.5× rate and 1 DBW and the 0.5× rate with 3 DBW compared with the 0.0× rate with 1 or 3 DBW. However, there was no indication that impatiens grown under different moisture levels had increased drought tolerance after application of Regalia®.
Traditional hollow-tine (HT) aerification programs can cause substantial damage to the putting green surface resulting in prolonged recovery. Despite the growing interest in new and alternative aerification technology, there is a lack of information in the literature comparing new or alternative technology with traditional methods on ultradwarf bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis (Burtt-Davy)] putting greens. Therefore, the objective of this research was to determine the best combination of dry-injection (DI) cultivation technology with modified traditional HT aerification programs to achieve minimal surface disruption without a compromise in soil physical properties. Research was conducted at the Mississippi State University golf course practice putting green from 1 June to 31 Aug. 2014 and 2015. Treatments included two HT sizes (0.6 and 1.3 cm diameter), various DI cultivation frequencies applied with a DryJect 4800, and a noncultivated control. The HT 1.3 cm diameter tine size had 76% greater water infiltration (7.6 cm depth) compared with the DI + HT 0.6 cm diameter tine size treatment. However, DI + HT 0.6 cm diameter tine size had greater water infiltration at the 10.1 cm depth than the noncultivated control. Results suggest a need for an annual HT aerification event due to reduced water infiltration and increased volumetric water content (VWC) in the noncultivated control treatment. It can be concluded that DI would be best used in combination with HT 1.3 or 0.6 cm diameter tine sizes to improve soil physical properties; however, the DI + HT 0.6 cm diameter tine size treatment resulted in minimum surface disruption while still improving soil physical properties compared with the noncultivated control.