DIFFERENTIAL-EFFECTS OF PRATYLENCHUS-NEGLECTUS POPULATIONS ON SINGLE AND INTERPLANTINGS OF ALFALFA GRASSES

The invasion by three different Utah populations of Pratylenchus negle ctus (UT1, UT2, UT3) was similar in single and interplantings of 'Laho ntan' alfalfa and 'Fairway' crested wheatgrass at 24 +/- 3 degrees C. Population UT3 was more pathogenic than UT1 and UT2 on both alfalfa an d crested wheatgrass. Inoculum density was positively correlated with an invasion by P. neglectus. Invasions by UT3 at all initial populatio ns (Pi) exceeded that of UT1 and UT2 for both single and interplanted treatments. The greatest reductions in shoot and root weights of alfal fa and crested wheatgrass were at a Pi of 8 P. neglectus/cm(3) soil. P i was negatively correlated with alfalfa and crested wheatgrass shoot and root growth and nematode reproduction. The reproductive factor (Rf ) for UT3 exceeded that of UT1 and UT2 in single and interplantings at all inoculum levels. There were no differences in Rf in the Utah popu lations in single or interplantings. A nematode invasion increased wit h temperature and was greatest at 30 degrees. Population UT3 was more pathogenic than UT1 and UT2 and reduced shoot and root growth at 20-30 degrees C. Soil temperature was negatively correlated with shoot and root growth and positively correlated with nematode reproduction. Repr oduction of UT3 exceeded that of UT1 and UT2 at all soil temperatures.