Published online by Cambridge University Press: 12 June 2017
Seeds of common yarrow (Achillea millefolium L.) germinated 99% with alternating temperatures of 15 and 25 C with concurrent dark and light periods. Germination was significantly higher when temperature was alternated, compared with a constant 15 or 25 C. Alternating light (8 h) and darkness (16 h) with either alternating or constant temperature significantly increased germination when compared with germination in the dark. After 9 yr, seed germinated over 41% under optimum conditions. Dicamba (3,6-dichloro-o-anisic acid) at 2.2 kg/ha reduced common yarrow infestations 90 to 95% in 3 of 4 yr, and 3,6-dichloropicolinic acid3,4 (designated D-290 in this paper) at 0.6 to 2.2 kg/ha controlled yarrow 90 to 100%. Yields on plots treated with D-290 at 0.6 kg/ha were significantly higher than those on plots treated with all rates of dicamba. Dicamba caused injury to grass and reduced its yield. Triclopyr [(3,5,6-trichloro-2-pyridinyl)oxy] acetic acid at 3.4 kg/ha was not effective on yarrow.