Search Results

You are looking at 1 - 3 of 3 items for :

  • Author or Editor: Gerald M. Henry x
  • HortTechnology x
Clear All Modify Search

No research has investigated the phytotoxic response of hooker’s evening primrose (Oenothera elata) plug transplants to preemergence herbicides. Varied phytotoxic responses of common evening primrose (Oenothera biennis) to preemergence herbicides suggest that options may exist for the safe control of weeds present within hooker’s evening primrose when grown as an agronomic field crop. Enhanced weed control during early establishment may reduce competition for water and nutrients as well as increase seed yield and oil content. Therefore, the objective of this research was to determine the phytotoxic effect of preemergence herbicides on hooker’s evening primrose plug transplants grown in the greenhouse. Research was conducted in 2010 and 2011 at the Plant and Soil Science greenhouse complex at Texas Tech University in Lubbock, TX. Herbicide treatments were applied on 13 July 2010 and 5 Apr. 2011 and consisted of oxadiazon at 3 lb/acre, isoxaben at 0.5 lb/acre, oryzalin at 2 lb/acre, prodiamine at 1.5 lb/acre, dithiopyr at 0.5 lb/acre, s-metolachlor at 1.8 lb/acre, pendimethalin at 0.6 lb/acre, and isoxaben + trifluralin at 2.5 lb/acre. One 4-month-old hooker’s evening primrose plug (2 inches wide) was transplanted into each pot (3 gal) 2 days after treatment (DAT). Dithiopyr and s-metolachlor treatments exhibited similar lack of phytotoxicity as the untreated control 7 DAT. Phytotoxicity ≥13% was observed for trifluralin + isoxaben, pendimethalin, prodiamine, oryzalin, isoxaben, and oxadiazon 7 DAT, with the highest level of phytotoxicity (24%) exhibited by trifluralin + isoxaben treatments. Hooker’s evening primrose phytotoxicity decreased (plants grew out of the damage) for all treatments except trifluralin + isoxaben, pendimethalin, and oryzalin 28 DAT. Oryzalin (16%) and trifluralin + isoxaben (60%) were the only two treatments that did not exhibit similar phytotoxicity to the untreated control 28 DAT. There were no significant differences in aboveground or belowground biomass nor plant growth index (PGI) of any of the treatments when compared with the untreated control 28 DAT. Based upon the results of this trial, pendimethalin, prodiamine, dithiopyr, s-metolachlor, oryzalin, isoxaben, and oxadiazon may be used for preemergence weed control in hooker’s evening primrose without causing excessive phytotoxicity (>20%), potential yield loss, or both. Trifluralin + isoxaben treatments exhibited 60% hooker’s evening primrose phytotoxicity 28 DAT, which resulted in too low of an initial plant stand to warrant use.

Full access

Metamifop is a postemergence aryloxyphenoxypropionic acid herbicide used for the control of annual and perennial grass weeds in cereal crops and rice (Oryza sativa L.). Previous research observed creeping bentgrass (Agrostis stolonifera L.) tolerance to applications of metamifop, suggesting utilization for the removal of encroaching bermudagrass (Cynodon Rich.) from creeping bentgrass putting greens with little to no phytotoxicity. Therefore, the objective of our research was to evaluate the efficacy of metamifop for common bermudagrass [Cynodon dactylon (L.) Pers.] control in a greenhouse environment. Experiments were conducted at the Plant and Soil Science greenhouse facility at Texas Tech University in Lubbock in 2011 and 2012. ‘Riviera’ and ‘Savannah’ common bermudagrass were seeded at 218 lb/acre into 4-inch square pots containing a soilless potting media on 26 Aug. 2011 and 14 Nov. 2011. Pots were allowed to mature in the greenhouse over a 3-month period where they were maintained at a height of 0.25 inches. Herbicide treatments were applied on 1 Dec. 2011 and 8 Feb. 2012 and consisted of metamifop at 0.18, 0.27, 0.36, or 0.45 lb/acre. A sequential application of each treatment was made on 22 Dec. 2011 and 29 Feb. 2012. A nontreated control was included for comparison. Clipping ceased after initial herbicide treatment and pots produced biomass for 3 weeks. Biomass above 0.25 inch was removed from each pot, dried, and weighed. This procedure was conducted again 3 weeks after sequential treatments. The rate of metamifop required to reduce bermudagrass growth 50% (GR50) was calculated 3 and 6 weeks after initial treatment (WAIT). Visual ratings of percent bermudagrass control were recorded weekly on a scale of 0% (no control) to 100% (completely dead bermudagrass). As metamifop rate increased, bermudagrass biomass decreased. The calculated GR50 at 3 WAIT for ‘Savannah’ and ‘Riviera’ was 0.19 and 0.14 lb/acre, respectively. Nontreated control pots exhibited 0% control and produced 0.59 to 0.83 g of biomass at 3 WAIT, regardless of cultivar. Metamifop at 0.27 to 0.45 lb/acre exhibited 96% to 100% bermudagrass control at 3 WAIT, regardless of cultivar. Bermudagrass subjected to those same treatments only produced 0.01 to 0.03 g of biomass at 3 WAIT, regardless of cultivar. The 0.18-lb/acre rate of metamifop exhibited only 9% control of ‘Savannah’ bermudagrass with 0.72 g of biomass collected, while ‘Riviera’ was controlled 41% with 0.38 g of biomass collected. The calculated GR50 at 6 WAIT for ‘Savannah’ and ‘Riviera’ was 0.13 and 0.14 lb/acre, respectively. Sequential applications of metamifop at 0.27 to 0.45 lb/acre completely controlled bermudagrass (100%) at 6 WAIT, while a sequential application at 0.18 lb/acre only controlled bermudagrass 8% to 19% at 6 WAIT, regardless of cultivar. Bermudagrass subjected to 0.18 lb/acre exhibited 0.48 to 0.56 g of biomass at 6 WAIT, regardless of cultivar. Metamifop shows potential as an alternative control option for common bermudagrass present within cool-season turfgrass species.

Full access

Indaziflam is an alkylazine herbicide that controls winter and summer annual weeds in bermudagrass (Cynodon sp.) turf by inhibiting cellulose biosynthesis. Research was conducted in Tennessee and Texas during 2010 and 2011 to evaluate the effects of indaziflam applications on overseeded perennial ryegrass (Lolium perenne) establishment and summer annual weed control. In Texas, perennial ryegrass cover on plots treated with indaziflam at 0.75 and 1.0 oz/acre measured 37% to 48% compared with 88% for the untreated control 257 days after initial treatment (DAIT). Perennial ryegrass cover following applications of indaziflam at 0.5 oz/acre measured 84% 257 DAIT and did not differ from the untreated control on any evaluation date. Inconsistent responses in crabgrass (Digitaria sp.) control with indaziflam at 0.5 oz/acre were observed in Tennessee and Texas. However, control was similar to the 0.75-oz/acre rate and prodiamine at 7.8 oz/acre at each location. A September application of indaziflam at 0.75 oz/acre followed by a sequential treatment at 0.5 oz/acre in March of the following year provided >90% control by June 2011. Indaziflam application regimes of this nature would allow for successful fall overseeding of perennial ryegrass every two years and control winter annual weed species such as annual bluegrass (Poa annua).

Full access