Host-Parasite Relationship of Meloidogyne chitwoodi on Potato

The soil fumigant 1,3-dichloropropene gave good to excellent control of the Columbia root-knot nematode, Meloidogyne chitwoodi, on potato, Solanum tuberosum L. Nonfumigant nematicides (aldicarb, fensulfothion, carbofuran, ethoprop, and phenamiphos) were less effective in controlling M. chitwoodi, since the nematode affects tuber quality more than quantity. Soil temperature during the growing season affected parasitism of M. chitwoodi on potato more than did the initial nematode population. There were positive linear correlations between degree-days and infected and galled tubers (r = 0.92), degree-days and nematode generations (r = 1.00), and infected and galled tubers and nematode generations (r = 0.91). Differences in degree-days and resultant nematode reproduction caused great variability in infection and galling of potato tubers during four growing seasons: 89% for 1979, 0% for 1980, 13% for 1981, and 18% for 1982, giving positive linear correlation (r = 0.99) between final nematode soil population (Pf) and percentage of infected and galled tubers. Corresponding increases in the soil populations of second-stage juveniles (J2) during the growing season were 9,700% in 1979, 170% in 1980,552% in 1981, and 326% in 1982. There was a negative linear correlation (r = -0.87) between initial soil J2 populations (Pi) and the degree of parasitism (infection and galling) of potato tubers, Pi being of secondary importance to degree-days.