ernst.cebert@email.aamu.edu; rward@aamu.edu Biofumigation in Combination with Conservation Tillage to Control Reniform Nematode in Cotton Ernst Cebert* and Rufina Ward, Alabama A&M University, Department of Plant and Soil Sciences, PO Box 1208 Normal, AL 35762 ernst.cebert@email.aamu.edu; rward@aamu.edu Abstract Reniform nematode (Rotylenchus reniformis), infecting most cotton growing areas in the southeast including Alabama, can reduce cotton yield by up to 75%. This study was conducted to evaluate cover crops as biofumigants in controlling reniform nematodes in cotton under conservation tillage system. Two mustard cultivars [Pacific Gold (Brassica juncea L.) and Ida-Gold (Sinapis alba L.)] and winter rye (Secale cereale, cultivar Maton) were used as cover crops in this study. Cotton plant stand and rate of growth were compared among plots without (control plots) and with cover crops. Our preliminary data showed that all cover crops used in the test significantly reduced reniform nematode populations (range <500 to 2,000/150cc soil) from the initial nematode level of >3000/150cc of soil sampled in early spring. Moreover, both mustard cultivars produced significant biomass before the first frost in 2003. The following spring, however, Pacific-gold and winter rye grew vigorously and produced large biomass but Ida-Gold minimally recovered from winter frost. Additionally, plots planted to Ida-Gold yielded lower nematode counts and sustained better cotton stand compared to those planted to Pacific Gold and winter rye. Based on these results, Ida Gold is a promising cover crop for controlling reniform nematodes in cotton. a Fig. 4. Pacific-gold (March 2004) Fig. 3. Ida-gold (March 2004) Fig. 1. Ida-gold (November 2003) Fig. 2. Pacific-gold (November 2003) b t Tests (LSD) for Nematode Count b b Comparisons significant at the 0.05 level are indicated by ***. Treatment Comparison Difference Between Means 95% Confidence Limits   Initial - Fallow 1215.5 -106.3 2537.3 Initial - Rye 1222.0 -99.8 2543.8 Initial - Pacific 1300.5 -21.3 2622.3 Initial - Idagold 1534.5 212.7 2856.3 *** Fallow - Initial -1215.5 -2537.3 106.3 Fallow - Rye 6.5 -1072.8 1085.8 Fallow – Pacific 85.0 -994.3 1164.3 Fallow - Idagold 319.0 -760.3 1398.3 Rye - Initial -1222.0 -2543.8 99.8 Rye - Fallow -6.5 -1085.8 1072.8 Rye - Pacific 78.5 -1000.8 1157.8 Rye - Idagold 312.5 -766.8 1391.8 Pacific_ - Initial -1300.5 -2622.3 21.3 Pacific_ - Fallow -85.0 -1164.3 994.3 Pacific_ - Rye -78.5 -1157.8 1000.8 Pacific_ - Idagold 234.0 -845.3 1313.3 Idagold - Initial -1534.5 -2856.3 -212.7 Idagold - Fallow -319.0 -1398.3 760.3 Idagold - Rye -312.5 -1391.8 766.8 Idagold - Pacific -234.0 -1313.3 845.3 NS Bridgeforth Farm, Athens, AL. September 2004. Photo 1. Reduced cotton stand in reniform nematode infested field is reflected by the actual number of nematodes found in soil samples (Table 1). No. of Nematodes per 100cc of soil NS Adult female embedded in cotton root There were no significant (NS) differences between treatments for nematode population and cotton stand. Principal component analysis (SAS, 2004) indicated replications and nematode population account for greater than 60% of the variation in the cotton crop (Figs. 8 & 9). Results The two Brassica cover crops produced significant biomass before the first fall frost (Figs. 1& 2). Cultivar, Ida-gold, however, failed to regenerate in the spring of 2004 (Fig.3), while Pacific-gold (Fig. 4) and rye cultivar (Maton) proliferated with increased biomass production in the spring of 2004. Population of the cotton crop was estimated within each treatment plot by counting plants in a 3.7-m2 in each plot. Plant growth was measured by height of 10 randomly selected plants within the same area. Each treatment was replicated four times. Sixty days after planting, soil samples were collected from each treatment for nematode analysis. Results showed that reniform nematode population significantly decreased from >3000/150cc to <500 - <2000/150cc of soil. The good stand of Ida-gold in the fall, while producing negligible biomass the following spring, resulted in lower nematode population and better cotton stand (Fig. 7). Cotton following Ida-gold showed less adverse effects to the cotton crop (Figs. 5 & 6). Abundant biomass produced by Pacific-gold in both fall and spring, resulted in less growth and lower stand-count of subsequent cotton crop. Our results showed that both Ida-gold and Pacific-gold supported better growth and stand of cotton than did rye as cover crop. Objective The objective of this study was to evaluate various Brassica species as biofumigant in reducing populations of reniform nematodes. Methodology The Bridgeforth Farm located in Tanner, AL (Limestone County), was used in this test due to the high population of reniform nematodes detected from soil tests conducted in summer 2002. Section of the farm associated with poor cotton stand and decreasing yields was heavily infested with reniform nematodes at >3,000 nematodes/150 cc of soil. One acre was selected within the nematode-infested area to evaluate the effectiveness of rapeseed (Brassica) as a potential winter cover crop that can help reduce the nematode problem. In the fall of 2003, the cover crops [rapeseed Pacific-gold (Brassica juncea) and Ida-gold (Sinapis alba) (Brown et al. 1997) and rye (Maton)] were planted in the no-till field after cotton crop was harvested. Growth of cover crops was monitored through spring. Conclusions Ida-gold poor winter tolerance had less adverse effects on the cotton crop. Better cotton stand growth. Pacific-gold good winter resistance had increased adverse effects on the cotton crop; lower cotton population and growth. Rye good winter resistance lowest cotton plant density lowest growth measurements (Figs. 8 & 9 ) Table 1. Nematode population and cover crop plots, (July 2004). 1Rye High Pacific Gold Very High Control* Ida-Gold Control Medium Rye 2,690 1Cover Crop *Control =Fallow Population level Very High = >1000 High = 500-999 Medium = 250-499 (reniform nematode count per 100cc soil) Analysis was done by Nematology Lab, Auburn University. Figures 8 and 9 References Brown, P.D. and M.J. Morra. 1997. Control of soil-borne plant pests using glucosinolate-containing plants. Adv. Agron. 61:167-231. Chitwood, D.J. 2002. Phytochecal Based Strategies for Nematode Control. Ann. Rev. Phytopathtol. 40:221-249. Halbrent, J.M. 1996. Allelopathy in the management of plant-parasitic nematode. J. Nematol. 28:8-14 SAS. 2003. PROC procedure.Ver. 9.1. SAS Institute Inc., Cary, NC, USA. Summary Effective management strategies towards nematode control are needed. Biofumigation using plants in the Brassicaceae (mustard) family such as rapeseed is a promising tactic for nematode control; glucosinolates, naturally occurring in crucifers, have nematicidal properties. Studies involving soil incorporation of Brassica crop residues have reported as high as 81% control of nematode. (Chitwood, 2002; Halbrent, 1996). Acknowledgment We are grateful to Mr. Billy Bridgeforth for the use of his farm. This project was funded Cotton Inc. (grant number 04-472AL) .