Effects of various rates of methsulfuron methyl on seed germination of some pine species

Weeds compete with forest tree seedlings for site resources and sunstantially reduce seedling establishment nd growth in nurseries and forest regeneration plots. Herbicides can cost-effectively and effectively control weeds in comparison to other traditional control methods. Herbicide screening of woody plant seeds has been successfully used for the selection of safe and effective herbicides for tree species. Consequently, research time and costs can be reduced when compared to the respective traditional field experiments. Metsulfuron methyl is a systemic sulfonylurea herbicide used to selectively control herbaceous and woody weeds in conifer plantations. In the present study, the cumulative germination rate and germination speed of Austrian, pine (Pinus nigra J.F.Arnold), Scots pine (P. sylvestris L.), maritime pine (P. pinaster Aiton) and Turkish red pine (P. brutia Ten.) seed presoaked in sulfometuron methyl solutions of 15 different concentrations (0-5% v: v), including a control, were evaluated in a rapid seed-screening trial in order to predict early field phytotoxicity of the herbicide on these pine species. At the end of the 28-day germination trial in the laboratory, the cumulative rate and speed of germination of the three pine species seed varied across different concentrations of sulfometuron. Sulfometuron methyl was not significantly phytotoxic to pine seed germination at low and intermediate concentrations, while seed germination was depressed at high concentrations. The herbicide appeared to affect germination speed more than cumulative germination. The use of this herbicide at low to intermediate concentrations in nursery beds and seeded forest areas could afford young seedlings a rapid establishment and growth without significant phytotoxicity to seed germination. These results could be used to predict early efficacy of sulfometuron on young pine seedlings in the field along with field confirmation of the results. Selecting a herbicide concentration that is both efficacious on weeds and safe for crop trees is vital for the successful establishment and growth of pine seedlings on nursery and plantation sites. Keywords: metsulfuron methyl, seed germination, phytotoxsite, pine, weed control.