Relationship Between Seasonal Population Growth of Columbia Root-Knot Nematode and Soil Degree Days in Potato.
1995. (Am Potato J 72:631). Ingham, R.E. and K.A. Rykbost
Populations of Columbia root-knot nematode (
Meloidogyne chitwoodi
) infective second stage juveniles (J2) were sampled weekly or biweekly from the top foot of soil within potato rows at Hermiston, OR during 1992-1994 growing seasons and at Klamath Falls, OR during 1994. Cumulative degree days (base temperature = 5 C) were determined at 4 and 8 inch depths. J2 densities in soil declined to nearly 0 after planting as J2 invaded crop roots. Rapid increase in J2 occured at Hermiston in late June, 1992 and in mid-July in 1993 and 1994 as J2 hatched from eggs. More degree days accumulated during the warmer season of 1992. J2 increase did not occur in Klamath Falls until August. However, the timing of J2 increase (which precedes tuber invasion) occured at 1200-1300 degree days in Klamath Falls and during all three years in Hermiston. This was only slightly behind that observed by Pinkerton, Santo and Mojtahedi in Washington. Rapid population increase occured at both locations and all years after 1200 degree days but since this point was reached closer to harvest in Klamath Falls, less tuber infection was noted in Klamath Falls than in Hermiston. Other potato infesting nematodes showed no relationship to degree days. Stubby-root nematodes (
Parathricodorus allius
) declined steadily through the growing season and root-lesion nematodes (
Pratylenchus neglectus
) remained relatively constant in number.
