Wake turbulence is a real and dangerous fact.The air behind an aircraft will move considerably and create turbulence,but it is the high-pressure air below the wings that will try to switch onto the low-pressure area above the wings that form wake turbulence in the form a high-rotation vortices.
Seen from behind,the right hand vortice will rotate counter-clockwise,while the left hand rotates clocwise.The vortices are much more powerful at situations where the wing produces maximum lift,that means during take-off and landing.At cruise altitude,the diff. between high and low pressure is not so pronounced,but they are still there,believe me!Next time you have a look at another plane producing contrails,you'll see it is really the vapor from the engines.Looking closely,for instance with a telescope or good binoculars,you'll see these contrails almost immediately they're behind the plane,they start to rotate very rapidly as they get in contact with the wing-tip vortices.As the rotational energy dissipates with time,the contrails will rotate more and more slowly,and fan out a bit to make wider stripes.How long they stay there depends on atmospheric conditions in that particular airmass,factors like pressure,temperature and humidity influence on the stability of the airmass.Clear-air turbulence will tend to dissipate the contrails more rapidly than in a stable airmass.Airmass might also be influenced by winds creating a wave-like condition and an airplane flying through this mass will produce contrails one moment,then nothing at all and finally contrails again as it enters air with the original conditions.
Basically,if your plane has a wingspan greater than the one in front of you,there isn't so much a problem with wake as if you're plane has a shorter span.In this case,you're completely within the turbulence area and ailerons are hardly effective,at all.
"Luck and superstition wins all the time"!