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Is it normal to see termites after fumigation?

It’s common to still see some termite activity after a professional fumigation treatment. Fumigation is very effective at eliminating termite colonies, but it usually takes time for all the termites to die off completely. Here’s what you need to know about termites after fumigation and when you should call the pros back for a follow-up treatment.

Why You May Still See Termites

There are a few reasons why termites can linger after a fumigation:

  • Some termites were deep in the wood or soil and avoided exposure to the fumigant gases.
  • Workers that were out foraging for food returned to the structure after the fumigation.
  • Neighbor colonies may move in to take over the niche left by the eliminated colony.

Fumigants like sulfuryl fluoride or Vikane gas diffuse through the wood and soil to kill termites. However, they can’t penetrate more than a few inches into dense areas. Deep nests inside wooden framing or in thick soil won’t get fully exposed.

Foraging workers out collecting food are also likely to survive. When they come back and don’t detect their nestmates, they wander around and try to start a new colony. New reproductive termites may also swarm to your home from nearby colonies.

How Long Should Termites Be Active After Treatment?

After a fumigation, termites may be active for anywhere from a few days up to a couple weeks. Here is a general timeline of what to expect:

  • 1-3 days: Many dead termites visible. Surviving termites appear sluggish or disoriented.
  • 5-7 days: Declining termite activity. Some cleaning and grooming behavior may be observed.
  • 10-14 days: Scattered termite sightings. Colony likely collapsed but stragglers remain.
  • 14+ days: Little to no termite activity noticed. Treatment was successful.

The fumigant gases dissipate fairly quickly, within 1-3 days. After that, the remaining termites’ fate depends on how much exposure they had and whether another colony moves in.

If termite activity continues at high levels past the first week, it could indicate a problem with the fumigation. Contact the pest control company if you still see a lot of termites after 7-10 days.

Signs that a Follow-Up Treatment is Needed

Here are some signs that termites are still actively infesting the home after fumigation:

  • Live termites spotted consistently over 3 weeks after treatment.
  • Swarmers emerging inside after the fumigation.
  • Mud tubes being built on foundation walls or other areas.
  • Damaged or hollowed wood that continues to grow.
  • Frass deposits around wood and termite tubes.

Occasional brief sightings of 1 or 2 termites can be normal die-off activity. But recurring evidence of colony activity requires further treatment. The ongoing structural damage also needs to be stopped quickly.

Why Fumigation Might Not Succeed

When fumigation fails to eliminate an infestation, there are some common reasons:

  • The colony was too large or widespread.
  • The fumigant did not penetrate wood or soil thoroughly.
  • The full recommended treatment time was not followed.
  • There are multiple termite species present.
  • Nearby colonies quickly moved in after treatment.

Failures due to incomplete exposure are more likely in particularly severe, long-standing infestations. Species like Formosan termites are also more tolerant of fumigants. Post-treatment monitoring and re-treatment of areas with continued activity are needed in these difficult cases.

Options for Follow-Up After Fumigation

If termites remain a problem after fumigation, your pest management professional has a few options for follow-up treatment:

Spot treatments

Localised spraying or dusting in areas where termites are still active can provide additional control. Products containing fipronil, imidacloprid or pyrethroids are common choices. Baits may also be placed around the structure to kill foraging workers.

Soil trenching and rodding

Rodding the soil with insecticide can kill subsurface termites missed by the fumigation. Trenching also allows insecticides to penetrate soil around the foundation.

Added fumigation time

Your home can be tented and fumigated again if activity is still high after 2 weeks. Adding extra time under the tarp may be more effective at penetrating wood and soil.

Heat treatment

Heating the infested area to over 120°F kills termites in wood and other materials. Temperature probes are used to verify lethal temperatures are achieved.

Wood replacement

Severely damaged wood is sometimes completely replaced if termites have penetrated deeply. This removes their food source and shelter.

Preventing Re-Infestation After Treatment

To help prevent termites from returning and re-establishing after a fumigation treatment, it’s important to:

  • Repair any moisture issues like leaks that make your home vulnerable.
  • Reduce mulch, wood debris, and vegetation touching the structure.
  • Ensure downspouts and gutters channel water away from foundation.
  • Install monitors and have regular professional inspections.

Making your home less hospitable to termites reduces the chances of new colonies moving in after elimination.

When to Call for More Termite Control

Contact your pest management professional if you see the following signs of an ongoing infestation more than 2-3 weeks after fumigation:

  • Live termites appearing frequently indoors.
  • New mud tubes forming on walls or foundations.
  • Damaged wood surfaces getting larger.
  • Evidence of swarmers emerging inside.

Make sure to save samples of any termites you find after treatment for identification. Early intervention with spot treatments and targeted fumigation can help nip renewed activity in the bud before it gets out of hand again.

With prompt follow-up inspections and re-treatment as needed, post-fumigation termite activity should end within 1-2 months.

The Takeaway

Seeing some termites after a fumigation or whole-structure treatment is common and not an immediate cause for alarm. The colony has been damaged and termites attempting to restart it will decline over several weeks. However, ongoing activity after 2-3 weeks likely indicates a need for supplementary control measures. With adequate follow-up by your pest management professional, a fumigation can still provide effective elimination despite occasional lingering termites.

Timeline after Fumigation Visible Termite Activity Interpretation
1-3 days Many dead termites, live ones appear sluggish Normal die-off
5-7 days Declining activity Treatment taking effect
10-14 days Scattered sightings Colony likely collapsed
14+ days Little to no activity Treatment successful
Signs of Continued Infestation Action Needed
Live termites seen consistently Spot treatment or added fumigation
New mud tubes appearing Insecticide rodding and trenching
Wood damage expanding Wood replacement
Swarmers emerging indoors Heat treatment