Response of Meloidogyne spp. to Pasteuria penetrans, fungi, and cultural practices in tobacco

The response of a mixed population of Meloidogyne incognita and M. javanica to three cultural practices, tobacco cultivars (two cultivars, differing in resistance to M. incognita), cover treatments (three treatments), and inorganic nitrogen fertilizer (two treatments), Pasteuria penetrans, and soil-borne fungi was investigated in a tobacco field in 1991. On all sampling dates, higher densities of root-knot nematodes were observed on tobacco cv. Coker 371 Gold than on K-326. Initially, forage sorghum decreased the number of Meloidogyne spp. on tobacco, compared with weeds and hairy indigo, but had little effect on the density of second-stage juveniles (J2) in soil at mid-season or final harvest. The density of P. penetrans endospores also decreased in soil in forage sorghum plots. On one of four sampling dates, high levels of inorganic nitrogen fertilizer increased the number of P. penetrans endospores produced per nematode female, and decreased the density of Meloidogyne spp. on tobacco. The density of P. penetrans endospores increased in these high-N plots after harvest, especially in the plots planted with K-326. The density of J2 in soil was negatively correlated with both the numbers of endospores attached per J2 and the proportion of J2 with attached endospores in midseason soil samples. No correlation was observed between the nematode density and frequency of fungi colonizing the egg masses of Meloidogyne spp.