Rotation crop effects on Pratylenchus penetrans and subsequent crop yields

Root damage from Pratylenchus penetrans causes economic losses in many crops. Rotation with poor or non-hosts is a control method that can reduce the use of fumigant nematicides. Short-term experiments were conducted to identify potential non-host sorghum and miller hybrids. In a field experiment, forage pearl millet (Pennisetum glaucum L. 'CFPM 101'), grain pearl miller ('CGPMH-1'), grain sorghum (Sorghum bicolor L. 'CGSH-7') and rye (Secale cereale L. common) were grown in rotation with tobacco (Nicotiana tabacum L. 'Delfield'), a known intolerant host. One rye treatment was fumigated prior to tobacco planting in 1998. P. penetrans numbers were lower in forage and grain pearl millet plots than in grain sorghum or rye plots in the year of planting. In the subsequent tobacco crop year, root nematode counts in plots where forage and grain pearl millet were grown were similar to counts in fumigated rye plots and lower than counts in plots where non-fumigated rye and grain sorghum were grown. Tobacco leaf yield was negatively correlated with soil nematode counts from November 1997 to July 1998 (r = -0.48, P = 0.0001), as well as with root counts from July 1998 to September 1998 (r = -0.40, P = 0.0015). This is the first report of P. penetrans suppression by P. glaucum in the field. Further investigation of nematode suppression by pearl miller lines and development of this potentially sustainable farming system is warranted.