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Management of Hardlock in Cotton in the Southeast

David L. Wright, James J. Marois, Matthew A. Vargas, and Pawel J. Wiatrak

ABSTRACT

The harvest season of 2002 was one of the most severe for hardlock in the humid areas of the cotton belt in recent history. Hardlock has been known to be a problem for years with unknown etiology and without any apparent means of control. Symptoms do not appear until the boll opens and the locks of cotton look more like a slice of an orange than a fluffed out boll of fiber. In many cases the quality of the fiber is not severely affected, but yields are reduced by 50% or more because conventional cotton pickers either knock the hardlocks to the ground or do a poor job of picking them. Due to the common occurrence of hardlock along the Gulf coast, there has been interest in strippers in UNR that could harvest all of the cotton regardless of hardlock. However, gin deductions, higher seed costs, and poor stands in narrow rows especially with reduced tillage has led to less interest and the dilemma of how to harvest the cotton produced. Hardlock has been found to be associated with high nitrogen, and high plant density. Studies in Quincy, Florida in 2002 correlated weather data of high temperature and high humidity to the amount of hardlock on the day of pollination or white flower. This correlation indicated infection was occurring on the day of pollination even though symptoms do not show up until boll opening. This study showed that fungi, especially Fusarium moniliforme, were also associated with the disease and the amount of cotton harvested could be increased with applications of the fungicide Topsin M. Fungicide applications made during the 8 weeks of bloom were the most effective at controlling hardlock and resulted in a 100% yield increase over the unsprayed, while applications made during boll opening increased yield about 30%. Fungicide application made at both flowering and boll opening did not increase yield significantly but did result in healthier plants. The fungicide delayed boll opening and natural defoliation by 7-14 days. The amount of hardlocked bolls was directly correlated with yield. Cotton seed weight and fiber length were increased significantly with applications of fungicide during the bloom period, perhaps due to bolls staying closed longer and developing further.





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Document last modified April 16, 2003