The relation between initial and final densities Pi and Pf in plots with 4 and 16 volunteer plants per m2 under oats was in reasonable agreement with the equation: Pf = a (— lnq)-1 (1 — qPi) + bPi, in which a → (Pf — bPi)Pi-1 when Pi → 0, b = the proportion of the eggs of the initial population, that did not hatch during the experiment and q a constant < 1. For both volunteer plant densities, b, as derived from the relation between Pi and Pf at medium and high values of Pi was 0.65. It is probably entirely due to spontaneous hatching. The high value of b suggests that the volunteer plants caused very few larvae to hatch. It is concluded that only larvae that hatched spontaneously, attacked and multiplied on the volunteer plants. It is also concluded, that high nematode densities are not influenced by the presence or absence of volunteer plants in cereals. Lower nematode densities may remain higher under cereals with volunteer plants than under those without. The lower the density of volunteer plants the lower the highest nematode density that is still markedly affected.
