Horizontal migrations of second-stage juveniles of Meloidogyne javanica in Sand in concentration gradients of salts and in a moisture gradient (l)

SUMMARY Horizontal migration of juveniles of M. javanica was studied in columns of sand in which was established either a moisture gradient or a concentration gradient of Salt oombined with a moisture gradient. The juveniles accumulated in the end of a moisture gradient having the highest moisture content. In ,concentration gradients of KH,P04, KNO,, Ca(NO,),, MgCI, and of Hoagland’s solution, the behaviour .of these nematodes in relation to the moisture gradient was reversed : i.e. the juveniles moved preferentially toward the region having the lower salt concentration which also had the lower moisture. The hypothesis is presented that at least in soils containing adequate quantities of mineral salts, a concentration gradient of Salt created by dilution of the soi1 solution along a moisture gradient. could induce a migration of the juveniles to the region having the lower salt concentration which is also the wet end of the moisture gradient. In this case a chemorepulsion could explain an apparent “hydrotaxis”.