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Growth and Yield Responses to Mepiquat-Type PGRs in Tennessee

C. Owen Gwathmey and C. Chism Craig, Jr.

ABSTRACT

Mepiquat chloride is widely used in cotton production in Tennessee, but producers lack clear information about crop responses to newer mepiquat-type plant growth regulators (PGRs). Field studies were conducted at Jackson TN in 1998, 1999, and 2003 to evaluate cotton responses to newer mepiquat-type products (Pix Plus, BAS 130, Pentia) relative to traditional mepiquat chloride formulations (Pix, Mepex) and untreated cotton. Growth responses to the newer products were generally similar to those of mepiquat chloride regardless of rate of application, cultivar or year. All the products promoted earliness during flowering by 5-10 days relative to untreated check. All products reduced final plant height similarly, by 4-14 inches relative to untreated cotton. Multiple applications starting at matchhead square controlled growth more than a single application at early bloom. Reduction in plant height was accompanied by production of 1-4 fewer fruiting branches. Boll retention at first and second position sites and total lint yield were not significantly affected by treatment in any test. Application of Mepex or Pentia increased percent of total yield picked at first harvest in DP 555 BR, relative to untreated check. Results provided no evidence that any of the newer mepiquat-type PGRs evaluated here are more effective than mepiquat chloride for growth control, or that any of these PGRs affect boll retention or total lint yield. Use of a mepiquat-type PGR is essential for controlling rank growth and promoting earliness in Tennessee cotton.





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Document last modified 04/27/04