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The efficacy, absorption, translocation, and metabolism of thiencarbazone-methyl (TCM) in hedge bindweed, field bindweed, ivyleaf morningglory, tall morningglory, and wild buckwheat were evaluated in greenhouse experiments and field trials. Forty-eight hours after foliar microapplication, ^sup 14^C-TCM absorption was highest in ivyleaf morningglory (60%), followed by field bindweed (50%), wild buckwheat (35%), tall morningglory (17%), and hedge bindweed (9%). In all species, ^sup 14^CTCM was translocated systemically. By 24 h after application, ^sup 14^C-TCM was detected in all parts of the plants. The translocation pattern is species-specific, with more translocation in tall morningglory and wild buckwheat. In all vining weeds ^sup 14^C-TCM was almost not metabolized whereas corn metabolized almost all ^sup 14^C-TCM 48 h after application. The efficacy of TCM was analyzed using dose-response curves. Wild buckwheat had the lowest value for the dose at which 50% of the activity occurs (2.1 g ai ha^sup -1^ TCM), followed by hedge bindweed and ivyleaf morningglory. Field studies confirmed the high control of wild buckwheat with TCM. Even at the lowest tested concentration of TCM, wild buckwheat was controlled by over 90%. In contrast, efficacy of TCM in field trials against perennial vining weeds was very low, 25% for field bindweed and 65% against hedge bindweed. Control efficacy could be well explained by the translocation pattern of TCM in vining weeds.
Nomenclature: Thiencarbazone-methyl; field bindweed, Convolvulus arvensis L. CONAR; hedge bindweed, Calystegia sepium (L.) R.Br. CAGSE; ivyleaf morningglory, Ipomoea hederacea Jacq. IPOHE; tall morningglory, Ipomoea purpurea (L.) Roth PHBPU; wild buckwheat, Polygonum convolvulus L. POLCO; corn, Zea mays L. ZEAMA.
Key words: Corn, mode of action of herbicide, vining weeds, weed control.
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The perennial weed species hedge bindweed and field bindweed and the annual weeds ivyleaf morningglory, tall morningglory all belonging to the family Convolvulaceae; along withwild buckwheat from the family Polygonaceae they are are characterized by their vining habits. This enables them to climb up neighboring plants, sometimes causing lodging of arable crops such as corn and wheat (Triticum aestivum L.) (Radosevich et al. 2007). Vining weed species strongly compete for light water and nutrients and cause high yield losses in agricultural crops (Holm et al. 1977). Leaves and stems of morningglories contain trichomes and 200 stomata mm22 on the...