Effects of Soil Temperature and Planting Date of Wheat on Meloidogyne incognita Reproduction, Soil Populations, and Grain Yield.

Wheat cultivars Anza and Produra grown in winter in California were planted in Meloidogyne incognita infested and noninfested sandy loam plots in October (soil temperature 21 C) and November (soil temperature 16 C) of 1979. Meloidogyne incognita penetrated roots of mid-October planted Ataza (427 juveniles/g root), developed into adult females by January, and produced 75 eggs/g root by harvest in April. Penetration and development did not occur in late plantings. Anza seedlings grown in infested soil in pots buried in field soil in early spring were not invaded until soil temperature exceeded 18 C. Meloidogyne incognita juveniles can migrate through soil and penetrate roots at temperatures above 18 C (activity threshold), however development can occur at lower temperatures. Grain yields were not significantly different between nematode infested (3,390 kg/ha) and noninfested (2,988 kg/ha) plots. Winter decline of eggs and juveniles in two late plantings anti in fallow soil were 69, 72, and 77%, respectively, but egg and juvenile decline was only 40% in the early Anza plots that supported nematode reproduction in the spring. Delay of planting date until soil temperature is below 18 C is suggested to maximize the use of wheat in rotation as a nematode pest management cultural tactic for suppressing root-knot nematodes.