Common Russians usually prefer to ignore any kind of potential danger (at least in much bigger degree than Europeans and Americans). So I believe that nobody really afraid of killer cucumbers. But AFAIK Russian officials often overreacts with such issues. I think it is made for political reasons. Everybody knows that political authority can handle such situation easily so cucumbers are merely a good reason to held some negotiations with counterpart and settle the situation for some bonuses (either big or small).