Mode of Transmission of Corynebacterium insidiosum by Ditylenchus dipsaci.

Transmission of Corynebacterium insidiosum (McCull.) Jensen (cause of bacterial wilt in alfalfa) by the stem and bulb nematode Ditylenchus dipsaci (Kiihn) was demonstrated by Hawn (3) . Disease development in plants where D. dipsaci was the vector was comparable to that in the controls where wilt was induced by the root-ball soak method devised by Cormack, Peake and Downey (1) . Furthermore, the development of wilt was stimulated by this complex because the nematode itself lowered bacterial wilt resistance in alfalfa (4) . Since a 1963 study (3) showed that the lumen of the buccal stylet was too narrow to permit ingestion of C. insidiosum, the possibility that the bacterium was carried on the cuticle of D. dipsaci needed further investigation. This paper reports the results of additional work performed to elucidate bacterial wilt transmission by D. dipsaci.