Weekly in-season Updates
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INFORMATION |
September 19, 2005 Talkin’ Cotton
Some of the early planted shorter season cotton varieties are quickly approaching the time for harvest aid application. Timing of the application is important, too early and quality may suffer, and too late and part of the crop may be lost due to weathering. There are three primary methods to help determine when the crop is ready for boll openers and/or defoliants. The first and oldest method is percent open bolls on the plant. Boll openers are usually applied when at least 65 percent of the bolls on the plant are open. Desiccants are normally applied when at least 85 percent of the bolls are open. You do not need a boll opener if the top harvestable boll will crack open with hand pressure. This indicates that the abscission layer of cells on the boll has formed and the boll will open when dried down. The second method is use of a sharp knife to cut through the top harvestable boll. A boll that is ready for application of an ethephon type boll opener will be difficult to cut open, and the inside of seeds in the boll should be solid with absence of any gel type material. The outside of each seed should have a dark seed coat that is evident on seeds that have been cut. The third method is called the nodes above cracked boll technique. First we need to locate the top first position boll that we can realistically harvest. If that boll is within 4 nodes of the uppermost first position cracked boll, a boll opener can be applied to the cotton.
Materials used early in the application season are usually a boll opener in combination with a defoliant. Finish works two to four days faster than other ethephon based materials, but is also slightly more expensive. Defoliants used in combination with boll openers may be Ginstar, Def, or Aim. Ginstar works best on cotton that has a lot of regrowth in the top of the plant or if the plant is drought stressed. Def, in combination with a boll opener is excellent for leaf removal, but is less effective in removing juvenile growth. Aim is more effective in burning down weeds such as morningglory in cotton to allow for harvest without the vines causing problems in the machinery. In severe cases, Aim may need to be applied again in 7 to 10 days to further desiccate the vines and condition the crop for harvest. In future articles, I will report on what chemicals and mixtures have been working well in this area.
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