Soil incorporation of waste asparagus rootstock from rootstock planting forcing culture reduces soil densities of Pratylenchus penetrans (Cobb) and damage to subsequent lettuce yield

We tested the utilization of waste rootstocks of asparagus forcing culture as a control agent of Pratylenchus penetrans in lettuce production. When asparagus waste rootstocks used in forcing culture were mixed with P. penetrans naturally infested soil, population densities of P. penetrans declined. Subsequently cultivated lettuce plants of incorporated plots had better growth and higher yield than those of the non-treated control. Waste rootstock mixed with P. penetrans naturally infested soil in glass jars at an incorporation rate of 1% (w/w) rootstock significantly lowered P. penetrans densities. Rootstocks were incorporated at 11 kg/m2 (equivalent to 1% of plowed soil) into nematode infested field plots in late April of 2006, and at rates of 5.5 kg/m2 or 11 kg/m2 into other plots in early May of 2007. At the beginning of September in 2006, P. penetrans population densities in the 11 kg/m2 incorporated plot declined to 16% of the control and in July 2007 to 23% and 11% of the control in the 5.5 kg and 11 kg/m2 plots, respectively. Lettuce seedlings were then transplanted to the field plots and the head weights and above-ground weights at the harvest were higher in the incorporated plots than the control in both years. Lettuce seedlings were again transplanted to the same field in March of the next year, and the 11 kg/m2 plots gave effective control results.