ALDEVAUX

Hello Moni, I must add that phytophtora can not only be water born in the soil but can also be air born by the chlamydospores which can resist dessication and be transported good distances with the wind or with soil particles. Its is only after it has landed on a host plant (leaves, bark etc.) that it needs free water for germination and infection. That is why I said you must be carefull only during long rainy periods and overhead misting.
It can also live in the soil but I do not know if P. ramorum infects the roots of plants (P.infestans which causes potato late blight does not infect roots of potato plants)
However, since the fungus can live in soil it can easily contaminate tools and this is why tool disinfection is an important method to prevent its dissemination. The method of disinfection described by Matt is supposed to be quite effective for most parasitic organisms that cause plant diseases.
But I must repeat that even if contaminated tools bring pores of the fungus on the trees (bark or leaves) they absolutely need free water for many hours before infection can take place.
I hope I made my point a little clearer.
Regards, Alain