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Submitted to: Journal of Cotton Science
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 9/14/2017 Publication Date: 10/1/2017 Citation: Timper, P. 2017. Rye residue levels affect suppression of the southern root-knot nematode in cotton. Journal of Cotton Science 2017. 21:242-246. Interpretive Summary: In the southeastern United States, rye is frequently planted as a winter cover crop in conservation tillage cotton. Although rye produces toxic compounds which may play a role in nematode suppression, it is also a host for the southern root-knot nematode, a major pathogen of cotton in the USA. The objective of this study was to determine whether a high-residue rye cover crop would reduce populations of root-knot nematodes compared to fallow soil and the standard rye cover crop. The study was conducted in a field infested with the nematode. Nematode numbers and cotton root galling were highest in the standard rye, lowest in the high residue rye, and intermediate in the fallow treatment. However, cotton yield increases following high residue rye were not enough to offset the cost of winter cover planting and planting high-residue rye solely for suppression of M. incognita is probably not economical. However, if farmers plant high-residue rye to improve soil structure and control of glyphosate-resistant Palmer amaranth, then they may also benefit from lower populations of root-knot nematodes. Technical Abstract: In the southeastern United States, rye (Secale cereale) is frequently planted as a winter cover crop in conservation tillage cotton. Although rye produces toxic benzoxazinoid compounds which may play a role in nematode suppression, it is also a host for the southern root-knot nematode Meloidogyne incognita, a major pathogen of cotton in the USA. The objective of this study was to determine whether a high-residue rye cover crop would reduce populations of M. incognita compared to fallow soil and the standard rye cover crop. The study was conducted in a field infested with M. incognita. The experiment was repeated four times from 2012 to 2015 and was a randomized complete block design with three cover crop treatments (weedy fallow, standard rye, and high-residue rye), each replicated eight times. At mid-season of the cotton crop, nematode numbers in soil were greatest in the standard rye, lowest in the high residue rye, and intermediate in the fallow treatment. After cotton harvest, the standard rye still had greater numbers of nematodes in the soil than the other cover-crop treatments. Root galling caused by M. incognita showed a similar trend as the mid-season numbers with the greatest galling in the standard rye and the lowest galling in the high-residue rye treatment. Planting high-residue rye solely for suppression of M. incognita is probably not economical. However, if farmers plant high-residue rye to improve soil structure and control of glyphosate-resistant Palmer amaranth, then they may also benefit from lower populations of M. incognita. |
