| Abstract/Contents: | Experiments were conducted to determine the effects of preemergence herbicides on root growth in common bermudagrass. Herbicides and rates used were: 1.6 and 3.3 kg ai ha-1 pendimethalin, 1.6 and 3.3 kg ai ha-1 oxadiazon, 0.5 and 1.1 kg ai ha-1 prodiamine, and 0.5 and 1.1 ai ha-1 dithiopyr. Both rates of prodiamine and dithiopyr reduced root fresh weight of common bermudagrass [Cynodon dactylon (L.) Pers.] and increased numbers of abnormal roots through 4 weeks after treatment (WAT). By 8 WAT, there were still more abnormal roots in plots treated with the high rate of dithiopyr or both rates of prodiamine than in untreated plots. The 3.3 kg ai ha-1 pendimethalin rate increased abnormal root numbers only up to 2 WAT. Preemergence herbicides were evaluated for control of perennial ryegrass (Lolium perenne L.). At 6 months after treatment (MAT), control ranged from 20 to 90%. Control of 80% or greater was achieved with 1.7 kg ai ha-1 pendimethalin or oryzalin, 1.7 + 1.7 kg ai ha-1 prodiamine or dithiopyr, and 3.4 kg ai ha-1 oxadiazon or benefin, 2.2 kg ai ha-1 simazine or diclofop, 13.4 kg ai ha-1 bensulide, 11.9 kg ai ha-1 DCPA, 0.8 kg ai ha-1 imazaquin, 4.5 kg ai ha-1 ethiozin or metolachlor, and 0.6 kg ai ha-1 pronamide. Perennial ryegrass was injured 4 MAT down slope (4:1 slope) as a result of lateral herbicide movement. Lateral movement was 170, 111, 110, 18, and 12 cm for 3.4 kg ha-1 oryzalin, 1.7 + 1.7 kg ha-1 benefin + oryzalin, 3.4 kg ha-1 pronamide, and 3.4 kg ha-1 pendimethalin, respectively. Weed control with clopyralid, the methylheptyl ester of fluroxypyr, the triethylamine salt of triclopyr, and the butoxyethyl ester of triclopyr was evaluated. Dicamba was also included for comparison. White clover (Trifolium repens L.) control was at least 80% with 140 g ae ha[superscript -1) clopyralid or dicamba, 216 g ae ha-1 fluroxypr, or 560 g ae ha-1 triclopyr ester, while control with triclopyr amine was less than 80% at rates of 560 g ae ha-1 or less. Copyralid provided the best control of dandelion (Taraxacum officinale Weber in Wiggers) of the herbicides evaluated, but control did not exceed 70%. Virginia buttonweed (Diodia virginiana L.) control was not improved by adding 8, 16, 3, 63 or 125 g ha-1 clopyralid or fluroxpyr with 28, 56, 112, or 224 g ae ha-1 2,4-D (butoxyethyl ester). Likewise, combinations of dicamba, MSMA, methazole, imazaquin, metribuzin, bentazin, primisulfuron, mesulfuron, quinclorac, or 2,4-D at recommended rates with clopyralid or fluroxpyr (16, 31, 63, or 125 g ha-1) did not increase control of Virginia buttonweed compared to similar rates of clopyralid or fluroxypyr alone. Combination of clopyralid and fluroxypyr (16, 31, 63, or 125 g ha-1) provided antagonism based on white clover fresh weights if the total amount of pyridine herbicide was less than 100 g ha-1. |
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