[red-indian]

The trench is about 4 inches wide. It's under the eaves. You can also do it on the inside of the building if you have a crawl space. Dig 10 ft of trench. Pour 5 gallons water in trench mixed with something like 1 oz neonicotinoid. Then backfill the trench. The neonicotinoid bonds with the soil and remains active for about a decade, stopping termites from entering the building. Any house meeting building codes is going to have a roof and eaves that prevent large amounts of rain from entering this area. The area has non-neonicotonoid soil on top of it so there's no casual run off. You'd have to have leeching through the soil to whatever watershed you have. This is impossible because the neonicotonoids bond with the soil and do not move once set.

With fruit trees it also has long lasting action, bonding with the very bark of the tree and remaining for many years. This is a problem since honey bees come to the tree and get microdoses which appear to mess with their navigation. But the interesting part is other pollinators don't show these effects. Which is perhaps because honey bees have the food they store (honey) harvested by their "keepers" and are then given commercial corn syrup mix (grown with pesticides and including residue) as their only food. The simplistic nutrition of this substance compared to real honey weakens these fellows, compounding the disorienting effects of the neonicotonoids.

In OP's Japanese study they are mass applying neonicotonoids directly to the surface of a watershed, which resulted in huge problems to the down stream aquaculture. This use of neonicotonoids is a terrible idea and the adverse effects were not surprising. I'm quite surprised that mass application of neonicotonoids to a watershed isn't considered a criminal act.

[markdown]

> stopping termites from entering the building.

Do the termites in your location not fly? In Fiji we have termite swarms once a year. Millions of them will show up at every light they can get to in the evenings. Everyone is advised to turn off their lights for a few hours and light a fire outside so as to get the termites to kamikazi. These are the Asian Subterranean Termites that arrived here via Australia.

Pesticide in a ditch around a house isn't going to stop these buggers.

[Gibbon1]

The idea is the poison kills them if they set up a nest next to the foundation.

[basicplus2]

Termites only fly when a colony has reached a limit on number, and pairs fly off to start new colonies.

unless they start a new colony inside the barrier, the barrier is still effective.

[dd36]

Subterranean termites.