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In Louisiana, sea oats (Uniola paniculata) are incorporated into beach restoration projects to build and stabilize sand dunes. Unfortunately, sea oats seed yield, germination, and seedling survival are poor. The objectives of this study were to assess the impact of commercial fungicide(s) on sea oats germination, seedling survival, and seedling quality. Sea oats seed were planted into soilless media and grown in greenhouse conditions in Baton Rouge, LA. Four fungicide treatments at two rates were applied to seeded trays: mefenoxam, thiophanate-methyl, azoxystrobin, and iprodione. Two control treatments were included: a 15-minute seed soak in water before seeding and dry seed. Percentage germination, percentage survival, shoot height, and fresh weight were measured. Sea oats seed treated with thiophanate-methyl at twice the fungicide label’s recommended rate [2× (23.0 oz/1000 ft2 a.i.)] had the greatest mean germination and survival and were the tallest seedlings 8 weeks after seeding. These results strongly suggest that treating seed with thiophanate-methyl 2× increased sea oats germination, survival, seedling quality, and profitability of sea oats production. The cost to apply thiophanate-methyl 2× to 1000 sea oats seed was $1.74. The additional revenue generated from greater germination, survival, and seedling quality when growing media was treated with thiophanate-methyl 2× was $37.72 per 1000 sea oats seeds. Therefore, the fungicide thiophanate-methyl was identified to be a practical and economical method to rapidly produce a large number of genetically diverse sea oats plants.
Swamp sunflower (Helianthus simulans) is an underused perennial plant native to the southeastern United States that produces an abundance of golden yellow inflorescences in the fall. It is a vigorous grower and tolerates a wide variety of soil conditions, growing in wetland and nonwetland habitats. Swamp sunflower warrants wider use in perennial beds and landscapes, and research on production practices to make plants more suitable for shipping could promote its production. This study evaluated the effects of plant growth regulators (PGRs) on the growth and floral attributes of the swamp sunflower. Treatments were applied to rooted cuttings in 1-gal pots as a substrate drench of 1, 2, 4, or 6 mg/pot paclobutrazol; 0.5, 1, 2, or 4 mg/pot flurprimidol; or water (control)/pot for Expt. 1. A second experiment (Expt. 2) applied 4, 6, or 8 mg/pot paclobutrazol; 2, 4, or 6 mg/pot flurprimidol; or water (control)/pot. Six weeks after treatment (WAT) for Expt. 1, paclobutrazol applied at 4 and 6 mg/pot and flurprimidol at 2 and 4 mg/pot resulted in smaller plants (as reflected by growth index) by 29%, 34%, 22%, and 48%, respectively, compared with the control. Furthermore, at the termination (6 WAT) of Expt. 1, the highest rate of flurprimidol produced the smallest plants, with the exception of the highest rate of paclobutrazol. By 6 WAT, plants treated with the highest rate of paclobutrazol and flurprimidol had lower dry weights and higher chlorophyll measurements than control. All PGR treatments for Expt. 2 resulted in smaller plants than the control by 27% to 36% at 4 WAT and 23% to 41% at 6 WAT. Differences for internode length and flower diameter were observed for Expts. 1 and 2, respectively. Results from these experiments suggest a substrate drench application of 6 mg/pot paclobutrazol or 4 mg/pot flurprimidol can be used for producing smaller plants compared with nontreated plants for swamp sunflower under greenhouse conditions.