Hardlock of cotton is when the fiber does not fluff out as the boll opens at maturity and looks like wedges of an orange when broken apart.  Although the quality of the cotton fiber may not be severely affected, conventional spindle harvesting equipment is not able to capture the fiber and bring it into the harvester.  The hardlocked cotton is knocked from the plant and falls to the ground or is strung out of the boll giving the appearance of poor harvesting procedures.

Hardlock of cotton seriously affects yield in many areas of the southeastern United States, and can be devastating in the panhandle of Florida.  In 2002 it caused over $20,000,000 in lost yield, reducing Florida’s average yield from 650 lb/acre to less than 400 lb/acre.  Hardlock is associated with high nitrogen, high plant density, high temperature and humidity, insect damage, and seed rot.  Because bolls affected by hardlock are not harvested by conventional pickers, farmers will not even attempt to harvest some fields with severe hardlock.  Although limited studies indicate that the quality of the fiber is adequate it is left in the field after harvest.  Attempting to “scrap“ the field by running the picker a second time to get the hardlock cotton often results in little lint and increased trash at the gin and discounted cotton.

A specific cause of the disease was not yet identified, and all past control efforts failed.  The purpose of this research is to identify the casual agent of the disease and to develop effective control measures against the disease.

Hardlock is differentiated from the traditional boll rots.  Boll rots usually are the product of insect damage or pathogen activity after the bolls have opened or early in the season when the carpel turns brown or black and never opens.  Boll rots occur during wet weather when the cotton boll or fiber is colonized by a number of pathogens, although only a few fungi are responsible for the majority of infections.  These include Alternaria gossypina (Thuem.) Hopkins, Curvularia spp., Diplodia gossypina Cke., Helmithosporium gossypii Tucker, Fusarium spp., and  Phomopsis .  

Thus far we have shown that the majority of hardlock is caused by the fungal pathogen Fusarium verticillioides, also known as F. moniliforme.  This is the same organism that causes corn ear rot.  We have shown that the main mode of infection is through the cotton flowers, and that fungicides applied to the flowers will control the disease.  This is an entirely new approach to the etiology and control of the disease and in 2003 field plots are replicated throughout the southeastern states in an attempt to reproduce the results developed at the NFREC at Quincy.  This has become a regional project with university faculty from Louisiana, Mississippi, Alabama, Georgia, South Carolina and Florida (NFREC and WFREC) working together, with major funding provided by Cotton Incorporated.

Other aspects of the disease being investigated at NFREC include the potential role of thrips in the epidemiology of the disease and the development of a disease forecast model to help growers time their fungicide sprays.  [Marois, Wright]

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