Pesticides, insecticides and chemicals are very emotive subjects with both beekeepers and non-beekeepers. I am not qualified to comment or to decide what material should be displayed on this website. The material left by Dave Cushman is well out of date and I have removed it as I think it may mislead the reader.
Many chemicals are no longer sprayed, but applied as seed dressing or in soil and compost. There is also the possibility of further threats from garden chemicals and those used to destroy other pests such as wasps. A further problem is the destruction of bees nests by some pest controllers, who don't seal off the treated nest. These can be accessed by bees who rob out any honey and take the chemical home with them, to do damage to their own nest. Partly for that reason I have removed the page on "Spray Liaison". In addition spray liaison schemes are not run by all beekeeping associations.
I have taken the view this website should not give any information on chemicals. It would be too easy to appear biased and it would be very difficult to keep up-to-date. There is a lot of material in the public domain and I can only point you to those sources.
As with other topics of this nature you will need to make yourself aware that some information may not be accurate, so you should seek it from authoritative sources.