ECOLOGY AND PATHOGENICITY OF THE HOPLOLAIMIDAE (NEMATA) FROM THE SAHELIAN ZONE OF WEST-AFRICA .8. SENEGALONEMA-SORGHI GERMANI, LUC AND BALDWIN, 1984 AND COMPARISON WITH ROTYLENCHULUS-RENIFORMIS LINFORD AND OLIVEIRA, 1940

The geographical distribution, host plants, population dynamics and ve rtical distribution were studied for the nematode Senegalonema sorghi in Senegal. The observations of sorghum roots parasitized by S. sorghi showed the absence of gelatinous matrix and the presence of a shell a round the mature females. The development of the female inside the roo ts induced the bursting and tearing of the cortical tissues of the roo ts. The factors influencing the multiplication rate and the effects of anhydrobiosis were studied in the laboratory for S. sorghi and Rotyle nchulus reniformis. The results showed that the highest multiplication rates of both species were recorded at relatively low soil temperatur e and high soil moisture. Both species were able to enter anhydrobiosi s during the dry season, with survival rates of 20-40%. S. sorghi para sitized only wild and cropped cereals. During the dry season, it was u nder hydrobiotic conditions at depth in cropped soils and under anhydr obiosis in the upper layers of the soils under fallow. The restricted distribution of R. reniformis in the vegetable crops under irrigation might be explained by its narrow host range; all other ecological char acteristics were the same as for S. sorghi.