Six countries currently require pesticide spraying on all inbound flights: Grenada, India, Kiribati, Madagascar, Trinidad and Tobago and Uruguay. Another six countries: Australia, Barbados, Fiji, Jamaica, New Zealand and Panama require the use of residual pesticides.
The
page isn't dated so I don't know how current it is.
I've never heard of the UK requiring it; perhaps there was a specific outbreak of something in 2009 or it could have been a spray other than pesticide.