Wards have a short delay before they enter stealth mode.
My question is, is the base attack speed of support and adc (without runes) sufficient enough to take down a ward at level one given that they have good enough reaction time?
EDIT: In Season 4 some wards have more than 3 hits of durability, so this will have to be updated.
Theoretically it's impossible at level 1 for conventional ADC/support lanes based on attack speed alone.
Wards take 1 second to become invisible after they are placed. The highest base attack speed at level 1 is 0.694, which means within a second only a single auto attack can hit the ward from a single champion. An ADC and support relying on auto attacks alone will not be able to take out the ward.
However, Vayne and Leona are notable for their auto attack reset upon using their Q ability, which allows them to land two auto attacks in quick succession. Leona can land a third auto attack if she manually targets the ward after using her Q. Any lane involving one of those two champions can clear at level 1.
Otherwise, some notable champions for clearing wards are (source):
As far as I'm concerned no, the fade time of a ward is too fast for an ADC and a Support to auto it to death.
However, Leona on her own can destroy a ward on her own at level 1 if she uses an auto attack, immediatly following up with Shield of Daybreak and then another auto since Shield of Daybreak resets the swingtimer.