The NFU told its members to check their kit to make sure it was not causing mayhem by going off through the night.
"Gas guns going off through the night do nothing to deter birds, waste gas and could end up attracting enforcement action," said a representative. "Check those timers."
Some local authorities used the NFU's 2006 code of practice to determine if a nuisance is being caused.
The code warns that thoughtless use risked "fuelling the pressure for strict legal controls or a ban on their use".
The guide said it may be possible to reduce the need for scarers and increase the effectiveness of those used by planting crops vulnerable to bird damage next to roads.
It urged growers to use as many different types of effective scarers as possible - visual, auditory and repellents to maintain the novelty that scared birds.
Growers ought to site scarers as far away from homes and hospitals as practicable, point them away from neighbours, and use baffles.
They should avoid using auditory scarers within at least 200m of sensitive buildings before sunrise, and take account of prevailing wind.