| Abstract/Contents: | "The genus Veronica, Scrophulariaceae, includes many species which are troublesome weeds in turf. Twelve species inhabit NY state, the most familiar being slender speedwell, (Veronica filiformis Sm., VERFI). The recommended control of VERIFI, DCPA at 13.5 kg/ha, does not provide adequate control. Little research has been conducted on control of the other weedy members of this genus. The focus of this paper is two-fold: 1)to distinguish among four weedy, stoloniferous perennials of Veronica, common speedwell (V. officinalis L., VEROF), germander speedwell (V. chamaedrys L., VERCH), thymeleaf speedwell (V. serpyllifolia L., VERSE), and VERFI and 2) to develop control recommendations for each species. Characterisitics such as leaf shape, degree of leaf blade serration, leaf pubescence, presence/absence of flowers and fruit, bloom time and flower morphology have been used to develop a key to this genus. A greenhouse screening of control of VEROF, VERFI, VERSE, and VERCH was conducted in winter 1989. The treatments included quinclorac at 0.11, 0.34, and 0.56 kg/ha, 2,4-D amine at 0.22, 0.68, and 1.1 kg/ha, triclopyr amine at 0.11, 0.34, and 0.56 kg/ha 2,4-D amine plus quinclorac at (1.1 plus 0.56 kg/ha, respectively), and triclopyr amine plus 2,4-D amine at (0.45 plus 1.0 kg/ha, respectively). At 6 weeks after treatment, 2,4-D (1.1 kg/ha) provided good control of VEROF and VERSE, but poor control of VERFI and VERCH. Quinclorac at 0.56 kg/ha provided >90% control of VERFI, VEROF, and VERSE and in combination with 2,4-D offered greater then 95% control of all species. Ninety percent control of VEROF, VERSE, and VERCH was obtained with triclopyr at 0.56 kg/ha, while the combination of triclopyr and 2,4-D provided excellent control of VERSE and VEROF, 84% control of VERCH, and poor control of VERFI. A field study was conducted at The LI Hort. Res. Lab, Riverhead, NY in June 1989 with herbicide treatments similar to the greenhouse study. Herbicide efficacy was lower in the field study than in the greenhouse. At 68 days after treatment (68 DAT), quinclorac at 0.43 kg/ha provided >90% control of VERFI and VERSE, 75% VEROF, 58% VERCH. Ninety-eight DAT, control was maintained at 80, 100, 55, and 26, respectively. 2,4-D provided 85% control of VEROF 68 DAT, but <50% control of the other spp. Quinclorac efficacy was not increased significantly by tank mixing with 2,4-D. Triclopyr did not control of any of the species; however, when combined with 2,4-D, VEROF was controlled 73% 68 DAT and 55% 98 DAT. In addition, this combination provided better control of VERSE than did either product applied alone. Overall, the Versonica spp. differed in susceptibility to the labeled herbicides. Control recommendations must be tailored to the species, making correct identification essential to successful control. The labeled herbicides provided inadequate control of all 4 spp. However, quinclorac controlled VEROF, VERFI, and VERSE in the greenhouse and field. No treatment provided better than 58% control of VERCH in the field study." |
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