Termite Swarm Season in Spain: What to Do Before April

Every spring in Spain, homeowners open a window and find a pile of tiny wings on the sill. They sweep them away, assume it was a passing ant swarm, and think nothing more of it. A year later, a surveyor finds a beam that crumbles at the touch.

Those wings almost certainly belonged to termites.

March is the last window of opportunity before Spain’s termite swarm season begins in earnest. If you own property here — especially an older home, a rural finca, or any building with wooden roof beams or window frames — this is the month to check.

Why Does March Matter for Termite Swarm Season?

Spain has three main termite species: the drywood termite (Kalotermes flavicollis) and two subterranean species — Reticulitermes grassei and Reticulitermes banyulensis. All three are found across the peninsula, with higher concentrations in the south, east, and the Balearic Islands.

Swarms — the moment when winged reproductive termites (called alates) leave the colony to start new ones — happen in late April through May across most of Spain. In the warmest coastal areas (Málaga, Valencia, Murcia, the Balearics), swarms can begin as early as mid-April when a warm day with mild winds follows a rainy spell.

The 2026 season is expected to be active. Research published in the Journal of Economic Entomology on large-scale termite elimination programmes in Spanish towns notes that bait consumption increases sharply in spring with rising temperatures — and that the mild winters of recent years have been allowing colonies to develop faster and expand their foraging range earlier. This trend, documented in towns like Íllora and Estepa, mirrors what pest controllers are seeing across the Mediterranean.

March, before soil temperatures peak and before alates take flight, is when:

• You can inspect without the pressure of an active swarm
• Professional pest controllers have availability (they become extremely busy from April)
• Bait stations installed now have time to be discovered by worker termites before summer
• Any necessary structural drying or sealing work can be completed before the humidity of spring

What Should You Check in Your Garden?

Subterranean termites — the most destructive species in Spain — live in the soil and travel to wooden structures through hidden mud tubes. Start your inspection outdoors.

What to look for:

• Mud tubes running up exterior walls, around foundation joints, or along pipes entering the building. These are roughly pencil-width and look like dried clay trails. They are the termites’ protected highways between soil and wood.
• Damaged or hollow-sounding wood around garden furniture, wooden fences, gate posts, pergola beams, or shed frames. Tap with a screwdriver handle — a hollow thud versus a solid knock tells the story.
• Discarded wings near soil-level cracks, under plant pots, or against the base of exterior walls. Wings from last year’s swarm may still be visible.
• Soil disturbance near tree stumps, old timber, or wooden fencing posts in direct ground contact.

How Do You Check Inside Your Property?

Subterranean termites work from the soil upward, so their damage often starts below ground level and progresses upward through walls. Drywood termites (Kalotermes flavicollis) are different — they infest wood directly without soil contact and are common in Andalucía, Catalonia, and the Balearics.

Indoor warning signs:

• Frass — tiny pale pellets that look like sawdust or coarse salt, found on floors or surfaces below wood. This is drywood termite excrement pushed out of their galleries.
• Blistered or bubbled paint on skirting boards, door frames, or wooden beams. This happens when termites have hollowed out the wood beneath.
• Doors or windows that suddenly stick — tunnelling can cause wood to warp.
• Sagging floors or ceiling sections — a later-stage warning indicating significant structural damage.
• Visible galleries in exposed timber: a network of smooth-walled tunnels, always cleaned of debris.

Pay particular attention to:

• Roof space and attic beams (especially in traditional Spanish houses)
• Skirting boards and parquet flooring near exterior walls
• Under kitchen and bathroom sinks where pipes enter wooden cabinetry
• The base of interior wooden columns or stairs

What Should You Do If You Find Signs?

If you find mud tubes, frass, or hollow wood, do not disturb the area beyond what you’ve already touched. Termites detect disturbance and will reroute away from treatments applied to exposed areas.

Your next step is to photograph what you’ve found and call a registered pest control company (empresa de control de plagas) registered with the Ministry of Health (ROESB — Registro Oficial de Establecimientos y Servicios Biocidas). For details on what professional treatment involves and what it costs in Spain, see our complete termites guide.

If you haven’t found anything, March is still the right time to install bait stations if your property is in a high-risk area — particularly if:

• It’s a pre-1980 property with original wooden beams
• It’s in a zone with known termite history (most historic centres in Andalucía, Valencia, and the Balearics)
• Neighbouring properties have had treatments in the past five years

Bait stations installed in late winter allow worker termites to find them as activity increases through spring. Colonies that begin feeding on bait can be eliminated over three to six months without any chemical soil treatment.

What Happens During a Termite Swarm?

If you do encounter a swarm — typically a sudden appearance of hundreds of winged insects clustering at lights or windows — this is what’s happening: a mature colony (at least three to five years old) is releasing its reproductive caste to start new colonies.

A swarm inside your home means there is an established colony already within or directly beneath your structure. Wings found on a windowsill may mean the swarm was outside and passing by, but wings found indoors — especially near skirting boards, roof space access hatches, or attic vents — are a strong indicator of internal infestation.

After a swarm, call a professional. The alates themselves are not destructive, but they confirm the parent colony exists and is large enough to reproduce.

How Do You Find a Pest Controller in Spain Before the Rush?

The window between now and mid-April is when reputable pest controllers are still taking new clients without long waits. From April onwards, phone lines at established companies get busy quickly.

When calling, ask specifically:

• Are they registered with the ROESB (Registro Oficial de Establecimientos y Servicios Biocidas)?
• Do they offer a written guarantee (garantía) with the treatment?
• What species are they treating for — subterranean, drywood, or both?
• Does the quote include the inspection, treatment, and any required follow-up visits?

For region-specific recommendations and what to expect from local companies, see the relevant guide for your area — for example, pest control in Andalucía covers the southern regions where termite pressure is highest.

The Bottom Line

Termite swarm season in Spain is approximately six weeks away. The colonies that will swarm in April and May have been growing silently for years. A 20-minute inspection of your property this week — checking for mud tubes outdoors and frass or hollow timber indoors — is low-effort insurance against a problem that, left undetected, can cost €10,000–€50,000 to repair.

If anything looks suspicious, don’t wait. Pest controllers are available now, treatments take effect over weeks, and the earlier a colony is targeted, the less structural damage you’ll be dealing with.

For the full picture on termite biology, treatment methods, and costs in Spain, read our in-depth termite guide.