The effects of cogongrass foliage and root residue extracts on germination and radicle and coleoptile growth of barnyardgrass, browntop millet, bermudagrass, hemp sesbania, Italian ryegrass, and prickly sida were investigated in laboratory experiments. Liquid extracts of cogongrass foliage and root residues at concentrations of 0, 0.25, 0.5, 1, 2, 4, and 8% were evaluated on bermudagrass and Italian ryegrass. Effects of 8% foliage or root residue extracts were investigated on hemp sesbania, prickly sida, barnyardgrass, and browntop millet. Cogongrass residue (foliage and root) extracts at concentrations as low as 0.5% inhibited germination and seedling growth of bermudagrass and Italian ryegrass. Germination of bermudagrass and Italian ryegrass was reduced by as much as 62% and radicle and coleoptile growth by as much as 96% at the highest extract concentrations. Foliage and root residue extracts reduced germination of barnyardgrass, browntop millet, and prickly sida 52 to 64% and seedling growth by as much as 96%. Cogongrass extracts had no effect on germination or seedling development of hemp sesbania. Results indicate that extracts of cogongrass may contain allelochemicals that may contribute to its invasiveness and extreme competitiveness.
Nomenclature: Barnyardgrass, Echinochloa crus-galli (L.) Beauv. #3 ECHCG; bermudagrass, Cynodon dactylon (L.) Pers. # CYNDA; browntop millet, Brachiaria ramosa (L.) Stapf. # PANRA; cogongrass, Imperata cylindrica (L.) Beauv. # IMPCY; hemp sesbania, Sesbania exaltata (Raf.) Rydb. Ex A. W. Hill # SEBEX; Italian ryegrass, Lolium multiflorum Lam. # LOLMU; prickly sida, Sida spinosa L. # SIDSP.
Additional index words: Allelopathy, coleoptile, germination, plant extracts, plant residues, radicle.