Tagetes patula is well known to be able to diminish Pratylenchus penetrans (Cobb) populations. In a field experiment, the increase of the P. penetrans soil population density after growing T. patula was significantly less than after chemical soil fumigation with metam sodium. The effect of T. patula on P. penetrans population densities lasted longer than the effect of chemical soil fumigation. Strawberries were grown for 3 consecutive years after T. patula without damage by the root lesion nematode. Assuming a linear rate of increase of the P. penetrans population density, we predict that strawberries could be grown for about 7 successive years without economic damage due to the root lesion nematode. Strawberry yield was greater from the crop grown 3 years after T. patula than that after soil fumigation 4 years previously. About 2 t strawberry yield increase is necessary to allow the growth of Tagetes every 5th year, without economic loss. The possibility of growing both strawberries and Tagetes in the same year should be investigated.