Canola, Camelina, and Fumigation Mustard Crop Rotations for Alfalfa Stem Nematode Control.

Alfalfa Stem Nematode (ASN), Ditylenchus dipsaci, is an important alfalfa pest in the state of Utah.  Symptoms are manifest as stunted plants, slower spring “green up”, poor stand density, weed infestations, and losses in forage yield and quality.  Current control methods include prevention by sanitation, crop rotations for two or more years with a non-host crop, and pesticide treatments.  Other control methods are needed for an improved integrated pest management strategy.  The use of a fumigation mustard crop rotation has been shown to provide nematode control in wheat and potatoes in the Pacific Northwest.  There is also a considerable interest in growing oilseed mustard crops, canola and camelina, as sources of biodiesel.  This project was initiated to determine the possible ASN control benefits from a biofumigant mustard, spring canola, and camelina crop rotation as compared to a traditional oat hay rotation.  A nematode infested alfalfa stand in Millard County was selected for study with three replications of the four crop rotation treatments being planted in spring 2007.  Pre-plant soil samples from all plots were taken and analyzed for ASN.  The oat or control treatment was swathed and baled for oat hay.  The fumigation mustard was mown and tilled into the soil when the plants were green.  Canola and camelina crops were randomly split into two half treatments with the whole plants being tilled into the soil and the other half being harvested for seed and the crop stover being tilled into the soil.  The field was then replanted to alfalfa.  Treatment effect on ASN will be measured in 2008 by soil and plant nematode infestation levels, alfalfa stand density, and forage yield.