Thursday, January 11, 2007 - 2:00 PM

Tropical Spiderwort as a Host for Nematodes During Crop Rotation Sequences

Richard F. Davis1, Timothy B. Brenneman2, and Theodore M. Webster1. (1) USDA-ARS, Crop Protection and Management Research Unit, P.O. Box 748, Tifton, GA 31793, (2) University of Georgia, P.O. Box 748, Tifton, GA 31793

Nematodes are the most damaging pathogens of cotton, and one of the most important pathogens of peanut in the US. Crop rotations utilizing cotton, peanut, and corn can be used to manage the southern root-knot (Meloidogyne incognita), peanut root-knot (M. arenaria), and reniform (Rotylenchulus reniformis) nematodes, though weeds can support reproduction and reduce the effectiveness of rotation as a management tool. This study documents the relative host status of tropical spiderwort (Commelina benghalensis) for M. incognita, M. arenaria, and R. reniformis. A reproductive factor (RF) was calculated for each nematode as the final population level divided by the initial population level (Pf/Pi). Galling was estimated on a 0 to 10 scale for the Meloidogyne species. Data from two trials with M. incognita were statistically similar, so a combined analysis was performed. Data from trials with M. arenaria also were combined, but data from trials with R. reniformis could not be combined. Meloidogyne incognita reproduced well on C. benghalensis, leading to a mean gall rating of 3.1 and a mean RF of 15.5 on C. benghalensis. Meloidogyne arenaria also reproduced well on C. benghalensis, with a mean gall rating of 2.1 and a mean RF of 7.2. In the first trial with R. reniformis, the RF was 2.4 on C. benghalensis and 1.4 on cotton. In the second trial, the RF was 3.6 on C. benghalensis and 13.5 on cotton. In summary, it appears that C. benghalensis is a sufficiently good host for some of the primary nematode pathogens of major crops in the southeastern US that its presence at high plant population densities can greatly reduce the nematode-suppressive effects of crop rotation.

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