PREVENTION OF TRANSMISSION OF THE CRAYFISH PLAGUE FUNGUS (APHANOMYCES-ASTACI) TO THE FRESH-WATER CRAYFISH ASTACUS-ASTACUS BY TREATMENT WITH MGCL2

Spore production of the fungus Aphanomyces astaci was prevented in vitro by the addition of MgCl2 to a concentration of 20 mM or more into the lake water used as sporulation medium. Mycelial growth in vitro in peptone-glucose agar was strongly reduced by 100 mM and completely prevented by 200 mM of MgCl2. When zoospores were used for infection at least 100 mM of MgCl2 was needed to protect the crayfish from infection. If crayfish were infected in lake water and then transferred to 25 mM or more of MgCl2, the fungus still grew within the cuticle but no sporangia were produced and the disease was not transmitted to uninfected A. astacus.