Postemergence Liverwort Control in Container-Grown Nursery Crops

Four experiments were conducted in Aurora, OR, and Auburn, AL, to evaluate effectiveness of herbicides for postemergence liverwort control. A sprayable herbicide, quinoclamine (Gentry 25-WP), was applied at rates between 1.8 and 7.6 kg ai/ha (1.6 and 6.8 lb ai/A), with or without a surfactant, and in spray volumes of 1019 or 2037 liters/ha (109 or 218 gal/A). Across all experiments, postemergence liverwort control was good (>90%) at the lowest rate when liverwort infestation was light (liverwort covered ≤25% of the substrate surface with no sporocarps). When liverwort infestation was high (liverwort covered ≥60% of the substrate surface with some sporocarps present), or in conditions favorable to liverwort growth, control improved by using higher rates or including a surfactant. At the highest labeled rate (7.6 kg ai/ha (6.8 lb ai/A)), postemergence liverwort control up to 14 days after applications was 96 to 100% across all four experiments. Long-term liverwort control through 42 to 56 days after application varied depending on the location and time year, with control decreasing as environmental conditions allowed for increased liverwort vigor. Sodium carbonate peroxyhydrate (TerraCyte) provided poor to moderate control, and was largely dependent on liverwort vigor. Flumioxazin (BroadStar) provided unacceptable postemergence control across all experiments.

Eradication of Common Liverwort from a Soilless Growing Medium

Common liverwort (Marchantia polymorpha L.) is an increasingly troublesome weed in containerized plant production. Postemergence applications were made to try to eradicate established stands of liverwort. Treatments consisted of sprays of quinoclamine at 1× and 2× rates and oxadiazon at the highest label rate, broadcast applications of sodium carbonate peroxyhydrate at 1x and 3x rates and four granular herbicides (flumioxazin, oxadiazon, oxyfluorfen + pendimethalin, and prodiamine) applied at label rates. The granular herbicides were applied both alone and with the sodium carbonate peroxyhydrate treatments. Herbicides were applied to common liverwort growing on an 80% aged pine bark: 20% Sphagnum peat-based soilless growing medium contained in 10-cm diameter plastic pots located in a double-poly covered greenhouse. At 2 weeks after treatment (WAT), control was best (93% to 100%) for both quinoclamine and the 3× peroxyhydrate treatments, intermediate (68% to 83%) for the 1× peroxyhydrate treatments, and not significant for any of the preemergence herbicides used alone. At 4 WAT, slight regrowth was evident in plots in which the treatments had an initial effect and the 1x peroxyhydrate + flumioxazin was as effective as the 3× peroxyhydrate and the 2× quinoclamine treatments. At 6 WAT, control was excellent in the 3× peroxyhydrate and 1× peroxyhydrate + flumioxazin treatments. Control was less, but still evident, in the quinoclamine and other 1× peroxyhydrate treated plots. While none of the treatments had completely eradicated common liverwort in all replications at 10 WAT, control was still excellent to good in many of the peroxyhydrate + preemergence herbicide-treated plots.

The Use of Sodium Carbonate Peroxyhydrate to Treat Off-Flavor in Commercial Catfish Ponds

Sodium carbonate peroxyhydrate (SCP) was applied to seven commercial catfish ponds in Mississippi to study the effects of treatment on fish flavor and pond ecology. The seven ponds were treated on alternate days in the morning with two doses of SCP at 55 kg hectare−1 (average depth 1-1.6 m). In three of the ponds, a potent 2-methylisoborneol (MIB) producing planktonic Oscillatoria chalybea-like species that was initially present was absent from the water column after treatment. In addition, the fish from two of these ponds were judged on-flavor 7 to 10 days after treatment. The off-flavor chemicals in three other ponds were diminished when measured seven days after treatment and fish were harvested from two of these ponds 10-14 days after treatment. The fish from the other two ponds were harvested 21 days after treatment. In the sixth pond, the predominant algal species was a 2-methylisoborneol producing O. chalybea-like species at 380 cells ml−1 and the treatment was ineffective. The treatment was most successful when off-flavor was less than two months duration and where application of the chemical was accomplished uniformly over the entire pond surface.