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In the U.S., morningglories account for approximately 20% of the cotton yield loss due to weeds. This amounts to approximately $50 million annually excluding cost of control. They interfere with cotton production by reducing yield, harvest efficiency and sometimes stand. They also cause increased trash in harvested samples. At a density of 1 plant/0.9 m row, cotton yield was reduced 64, 42, 33 and 33% by tall, entireleaf, ivyleaf and pitted morningglory, respectively (Crowley and Buchanan, 1978). Stand was also reduced at higher densities. Entireleaf and ivyleaf morningglory at 16 plants/9 m of row reduced lint yield by 29% in notillage and 33% in conventional tillage (Shelby and Hayes, 1989). Morningglories cause grade reduction in cotton, but do not influence lint percentage, micronaire, fiber strength or length. The order of sensitivity of morningglory species to herbicides use in cotton production generally was pitted > entireleaf = ivyleaf > tall. Prometryn, cyanazine, oxyfluorfen and fluometuron were equally efficacious against all species. A mixed population of pitted, entireleaf and ivyleaf morningglory reduced lint yield 56% from 1260 kg/ha in the weedfree check. Fluometuron at 1.7 kg ai/ha alone or in combination with norflurazon at 0.8 kg ai/ha or norflurazon preplant incorporated at 1.7 kg ai/ha, each with two cultivations, prevented lint yield loss. Combinations of norflurazon and fluometuron were needed to prevent yield loss when common cocklebur, smooth pigweed, sicklepod and morningglory were present. Norflurazon at 0.8 kg ai/ha preplant incorporated was as effective as 1.7 kg ai/ha preplant incorporated or preemergence when used in combination with fluometuron. The most complete weed control system was preplant incorporated trifluralin at 0.8 kg ai/ha plus norflurazon at 0.8 kg ai/ha followed by preemergence fluometuron at 1.7 kg ai/ha plus norflurazon at 0.8 kg ai/ha in conjunction with one or more timely R.M. Hayes cultivations and/or post-directed herbicides such as cyanazine, oxyfluorfen, fluometuron, methazole, diuron or prometryn in combination with MSMA. |
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©National Cotton Council, Memphis TN |
Document last modified Sunday, Dec 6 1998
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