Chemical-soil termite barriers across Greater Darwin.

What goes in the soil.

The two non-repellent chemicals registered for in-soil termite treatment in the NT are Termidor SC (fipronil) and Premise 200SC (imidacloprid). Both work the same way: termites don’t detect them, walk through the treated soil zone, pick up a lethal dose, and (critically) carry it back to the colony before dying — transferring it to nestmates via grooming contact. This “transfer effect” is what makes non-repellent chemicals so much more effective than older repellent products (which termites simply avoid).

Termidor SC vs Premise 200SC — what we use when.

• Termidor SC (fipronil) — 8–10 year barrier life in Top End conditions. Strong transfer effect. Excellent against Coptotermes. Reasonable against Mastotermes if injection volumes are adequate. Our default for urban Darwin and Palmerston jobs.
• Premise 200SC (imidacloprid) — 10–12 year barrier life. Slightly slower kill (4–7 days vs Termidor’s 1–3 days). Preferred on porous Litchfield soils because it binds more tightly to soil particles — less leaching.
• For active Mastotermes infestation we typically combine: Termidor SC perimeter injection + Sentricon Always Active baiting + sub-floor enhancement injection. Belt and braces.

Injection volumes — Mastotermes needs more than Coptotermes.

Standard southern-Australia chemical-soil barrier injection is 5L/lineal metre of perimeter. For Top End jobs we typically use 7–9L/lineal metre on rural acreage where Mastotermes is present, because Mastotermes’ diffuse colony foraging means there’s wider colony pressure on the perimeter. Higher injection volumes mean a deeper / wider treated zone that’s harder for foraging Mastotermes workers to circumvent.

Reticulation tube vs hand-injection.

For pre-construction (AS 3660.1) or major renovation work, we install a reticulation tube around the perimeter and at slab penetrations — a flexible polyethylene tube with emitters that allows the chemical to be re-injected at 8–10 year intervals without re-digging the perimeter. Massive long-term saving on renewal cost. For existing buildings without a reticulation tube, hand-injection at 0.3m intervals around the perimeter is standard. Each injection point sits 100–200mm below ground level.

Renewal of expired pre-1995 organochlorine barriers.

Many Casuarina, Tiwi and Wagaman homes still have their original 1975–85 post-Cyclone-Tracy rebuild chemical barriers (chlordane, dieldrin, heptachlor). These organochlorines have very long persistence but are now banned. Some still test active 40 years later; many don’t. We test soil at inspection and only quote renewal where soil residue has degraded below threshold. Don’t assume an old barrier is expired without testing.

After the treatment.

• Termite Management Certificate (Form 16) issued for the property file
• Filed copy under the meter box or in the electrical sub-board
• Insurance-grade documentation
• Annual AS 3660.2 inspection recommended throughout the barrier life
• Re-test at 7 years to confirm chemical still active (Top End degradation faster than southern Australia)