I can't help with the uptake question. However, for an alternative to chemical pesticide check the cedarcide website. They Cedar oil is deadly to insects but safe for people.

Here is a link that might be useful: Cedarcide

First off I use to be in pest control, and they are not suppose to spray 25 feet of edibles, wildlife, or water sources. As for the chemical some have a residule that have been tested up to 10 years. It really depends on the chemical being used to do the pretreatment and the regular maintenace spraying. I know here in tennessee it is the state law they have to leave the chemical name on the receipt. So I would suggest looking at your ticket they left and if they didnt leave one I would call the company and ask them to pull your record to find the chemical being used. All pest control companies use different chemicals.

Secondly I know this is way easier said than done, but I would advise not planting your edibles around the immediate perimeter of your home. Mulch, dead leaf matter, twigs, old mowed grass, plastic all contribute to pest such as termites and ants. I would suggest having your evergreen shrubs around the perimeter of your home maybe with rock in the beds but no untreated mulch.

Thirdly subterranean termites are very rare here, they actually are different than the regular termite. They actually live under ground and dig tunnels under the house they are also harder to get rid of. So unless you plan on digging up your yard to get rid of your termites yourself I would stick with the proffessional let the blame be on him if they screw up.

Finally a last thought, me personally as someone that has been in pest control and has seen the damage that a termite can cause and how fast it can over take a house, I wouldnt get rid of the termite inspections. Your house is the biggest investment you will probaly ever make. I never knew how important it was to have at least a termite contract but when I did find out all the damage one colony of termites could cause I thought people were stupid for not having contracts.

Oh and some natural pesticides that are safe may work but you have to remember that it has to penetrate the ground for it to work. The standard for drilling the vents is one hole per 10 to 12 inches. Depending on pest in the area depends on the depth that the chemical can reach. So granted it may be safer to use chemicals that are safe to humans but if you dont know how to treat an area properly for the pest you are after then you just wasted your money and your valuable time.

The termite boys usually have tanks from anywhere between 25 to 100 gallon tanks. Depending on your house size and perimeter of your house would depend on how much chemical they would need. I dont know how much the cedarcide would cost to fill a 100 gallon tank. I would sure compare that though to the time and cost of just moving your plants.