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  • Author or Editor: Jennifer A. Pope x
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Specialty crops generate $40 billion in annual sales comprising a significant portion (40%) of total agricultural sales. The diversity of plant material is a limiting factor for new herbicide registration. The IR-4 program facilitates the labeling of new or experimental pesticides for minor use crops. The objective of this experiment was to determine the ornamental phytotoxicity and efficacy of Pendemethalin for selected 1-gallon perennials. Phytotoxicity was evaluated on Armeria maritime, Boltonia, Buddleaia davidii, Cercis Canadensis, Delphinium, Fragaria, Oenothera, Panicum virgatum, Papaver orientale, Phlox subulata, Rudebeckia fulgida, Scabiosa columbara, Schizachyrium scoparium and Sedum spectabile. Herbicide was applied at 1X, 2X, and 4X rates according to IR-4 protocols with a weedy check included. Pendemethalin was applied twice throughout the study, the second spray occurring two months after the first. Visual ratings were taken of efficacy (scale, 0-10) and phytotoxicity (scale, 1-10, 10 = complete kill) at 15 and 45 days after treatment (DAT). Buddleaia displayed symptoms of phytotoxicity at the 4x rate but grew out of the initial effects of the herbicide. By trials end, Oenothera at 1×, 2×, 4× rates, Fragaria and Phlox at 2× and 4× and Canadensis at 4× had significantly reduced plant quality. All remaining species had acceptable plant quality. Efficacy was evaluated following the same protocol as above with a weedy seed check using a 1/8th tsp.mixture of Digitaria sanguinalis, Poa annua, and Senecio vulgaris per 1-gallon pot. Overall no treatment provided an acceptable level of weed control. The herbicide provided little control of Groundsel, was moderately effective in controlling the Bluegrass, and provided 100% control of the Crabgrass.

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DNA herbicides are the most commonly used preemergents in container nursery crops. The objectives of this study were: 1) to investigate differences between DNA herbicide applied as granulars, directed sprays, or in combination with mulch (pine nuggets and cypress) on Taxus, Azalea and and Ilex root development; and, 2) to compare efficacy of the above treatments on common groundsel (Senecio vulgaris), large crabgrass (Digitaria sanguinalis), and annual bluegrass (Poa annua). The granular formulations tested were Barricade 65 WG (prodiamine) at 2.0 lbs active ingredient per acre (a.i./ac) and Treflan TR10 (trifluralin) at 2.0 lbs a.i./ac. The liquid formulations that were used as direct sprays and to treat the mulches were Surflan 4 AS (oryzalin) at 2.0 lbs ai/ac and Pendulum 3.8 CS (pendimethalin) at 3.0 lbs a.i./ac. Evaluations of phytotoxicity and efficacy were taken as rated scores, dry weights, and leaf area measures. Evaluations were taken at 30, 60, 90, and 120 days after treatment (DAT). Efficacy ratings were based on a 0-10 scale with zero being no control, 10 perfect control and 7 commercially acceptable. By 120 DAT, none of the treatments were commercially acceptable. Root (1.52 g) and shoot (3.75 g) weights indicate that Ilex was stunted the most vs. the control (2.42 g roots and 4.87 g shoots) by the direct spray of Pendulum 2X. The Azalea was most effected by the granular application of Barricade at the 2X rate (1.72 g for roots, 4.44 g for shoots) vs. the control (2.23 g for roots, 5.83 g for shoots). Taxus roots were most stunted by Treflan 1X (0.81 g) vs. control (1.01 g). Shoot weights were the lowest with Cypress+1X Pendulum (0.90 g), vs. the control (0.96 g); however, the Treflan 1X treatment gave the second lowest shoot weight for Taxus (0.91 g).

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The objective of this study was to evaluate the extent and duration of efficacy and phytotoxicity of two new formulations of dichlobenil (Casoron 50WP and Casoron CS), applied alone or onto two bark mulches, pine nuggets or shredded hardwood. The herbicide treated bark was compared to a control (weedy check), direct sprays of the herbicides and mulch alone. Three granular preemergent herbicides, dichlobenil (Casoron 4G) and two formulation of flumioxazin (Broadstar 0.17G, VC1351, and VC1453) were also evaluated for a total of 12 treatments. The trial started on May 23, 2003. Visual ratings and dry weights were evaluated for efficacy at 4, 8 and 16 weeks after treatment (WAT) and phytotoxicity 2, 4, 8, and 16 WAT. Ratings of efficacy were based on a 1-10 scale where, 0 represents no control, 10 represents complete control. Visual rating scores of 1 (no injury) to 10 (complete kill) were used for phytotoxicity on Salvia May Night. The two most efficacious treatments are Casoron CS as a directed spray (7.9) and treated on pine nuggets (9.0). The hardwood bark with Casoron CS also was providing an efficacy rating of 7.75 in the analyses of combined dates 4 and 8 WAT. The weed control provided by the untreated hardwood bark and pine nuggets was not significantly different from the control. Four treatments—Casoron CS and 4G, Casoron CS on pine, and CS on hardwood—provided ratings of 3 and above for phytotoxicity, in the analyses of combined dates 2, 4, 8, and 16 WAT. Although the Casoron CS was the second most efficacious treatment it had a phytotoxicity rating of 9.25 over combined dates. The CS on pine, however, had a significantly reduced phytotoxicity rating (3.5) and superior efficacy.

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