Do scorpions live inside the block wall itself?

Yes. University of Arizona Extension calls hollow-block perimeter walls a common bark scorpion association, and groups overwinter in protected spaces and sometimes turn up when block walls are taken down. The hollow cores stay shaded and stable through a Tempe summer. Cracks, missing mortar and open caps give them the way in, which is why those details matter so much.

Why do I only see scorpions on the fence at night?

Because that is when they move. University of Arizona Extension reports most movement between 7 and 11 p.m. and again from 3 a.m. to sunrise, with nights above 70 degrees ideal. By day they stay in cracks. A wall that looks empty at noon can show several after dark under a UV light, so judge your wall during a warm evening check, not a daytime walk.

Is it worth capping my block wall?

If the cores are open and you see scorpions there, it is a reasonable step. University of Arizona Extension lists stucco and caps on hollow-block walls as a way to make them less inviting. It is masonry work and may not stop scorpions already inside. On shared walls in Scottsdale and Tempe subdivisions, talk to the neighbor and check HOA rules first, since it is not your wall alone.

How far should plants and stored wood sit from a block wall?

About 24 inches for shrubs and trees, which is the clearance University of Arizona Extension gives for walls. Its guide also says to stack wood neatly, lift it 6 inches off the ground, and move loose boards and rocks away altogether. A narrow Tempe side yard may not allow that everywhere, so start with the stretch where your UV walk finds the most scorpions.

Should I kill the big hairy scorpions along my wall?

There is no need to. University of Arizona Extension calls the giant hairy scorpion a beneficial addition to a home landscape, because it eats bark scorpions voraciously. Adults often exceed 5 inches and stay under rocks and in shallow burrows, unlike the slim bark scorpion climbing your block. All scorpions can sting, so keep hands away in any Tempe or Scottsdale yard, but that one can stay.

How to Get Rid of Scorpions Around a Block Wall

Scorpion Control · By Kai Horner, owner of Kekoa Pest Control · Published 2026-11-02 · Updated 2026-11-03

Almost every Valley subdivision has one, and the scorpions know it. University of Arizona Extension says bark scorpions are often tied to homes and hollow-block perimeter walls. This post explains why, what to change, and how the wall fits into wider scorpion control in Tempe, Scottsdale and the rest of the low desert.

Why bark scorpions choose block walls

In harborage research reported by the university, 95 percent of bark scorpions chose hollow block walls over other options around buildings and landscapes. It is easy to see why. A hollow wall offers shade through a 110-degree afternoon, tight crevices, and a straight path along the property line.

They also tolerate each other. Bark scorpions are not territorial and often share cover, so one crack can hold several. In the coolest months they cluster in protected spaces, and groups have turned up when block walls were taken down in winter. Your wall may be doing more than you can see.

How to get rid of scorpions in a block wall, step by step

Pesticide on its own will disappoint you. The university says scorpions are difficult to manage that way, and it also says a yard free of them is not realistic. So this is a sequence of reducing cover, water, food and access. Do the free steps first.

Clear the base. Move wood, stacked pots, rock piles, pallets and debris away from the wall. The university says to wear leather gloves and take care when shifting yard items.
Fix the water. Repair leaking drip emitters and stop sprinklers wetting the wall. Irrigation floods scorpions out of one refuge and into the next, and it supports higher numbers.
Cut vegetation back. Keep shrubs and vines off the block, and prune branches away from the house. The university's figure is at least 24 inches of clearance from walls.
Count them. Do a UV walk along the wall after dark to find the active stretch.
Close what you can. Patch open mortar joints and broken caps, and leave drainage openings open.
Treat the line. Target the wall base, cracks and adjoining gravel, following the label.
Protect the house. Tighten door sweeps and screen weep holes with coarse steel mesh, so the wall problem stays outside.

Bark scorpion glowing under a black light on top of a concrete block wall — Hollow block walls give bark scorpions shelter by day and a path at night.

What treating the wall actually involves

A wall treatment is about placement. Most of the wall surface does not matter. The cracks, the cap line, the base where wall meets soil and any gap into the neighbor's yard matter a lot. Products are chosen for the site and applied according to the label, with care around bird baths, vegetable beds and spots pets use.

Keep your expectations honest on this point. Scorpions spend the day tucked in cracks, so a surface treatment does not reach every one, and a shared wall has a second side you do not control. If your neighbor waters heavily against the same wall, you will feel it. That is why a plan for a scorpion yard treatment usually looks at the whole yard rather than the wall alone.

Patching a block wall: what goes where

Not every opening gets the same repair, and one kind must stay open. This table matches University of Arizona Extension guidance to what you are likely to find along a Valley wall.

Opening	What to use	Why
Small crack	Silicone sealant rated for outdoor use	It handles heat and cold better than latex caulk
Missing mortar or a broken block	Mortar or cement	Larger openings need a strong material that matches the wall
Wider gap around a pipe or wire	Copper mesh, then sealant	The mesh fills the space before the sealant goes on
Open cores along the top	Masonry caps	The university lists capping to make walls less inviting
Weep holes in brick veneer or weep screed	Coarse steel mesh	They must not be plugged, because they ventilate the wall space

A patch is not a cure for what is already inside. Sealing a cap keeps new scorpions from dropping into the cores, but any already living there can still leave through a crack lower down, so walk the whole stretch.

A year along the wall

The calendar tells you which job to do when. These months follow the university's account of how bark scorpions behave in the low desert.

When	What scorpions are doing	Job for the wall
November to March	Less active, clustering in protected spaces	Daylight repairs. Expect groups if you open anything
April and May	Warming toward the nights they prefer	Fix irrigation, clear the base, cut plants back
June to September	Active, with nights above 70 degrees ideal	UV walks between 8 and 11 p.m.
After storms and heavy watering	Flooded out of refuges and on the move	Check the wall line and doors that evening

Keeping scorpions off the fence: what helps most

Some jobs pay off more than others. Here is how the common fixes compare.

Fix	Effort	Why it helps
Clearing stacked items from the wall	Low	Removes daytime shelter and shelter for prey
Repairing irrigation leaks	Low	Takes away water for scorpions and crickets
UV collection in summer	Medium	Removes scorpions directly, several nights a season
Patching mortar and caps	Medium to high	Fewer ways into the hollow cores
Stucco and full cap	High	The university lists it to make walls less inviting

Timing matters too. The university suggests UV collections several times in summer, between 8 and 11 p.m., with boots and long tongs. Do not use your hands, and keep kids well back. It also encourages releasing them in open desert rather than killing them, if you are willing to do that. Its pest-proofing guide goes further, saying repeated collections and releases far from the house beat repeated pesticide applications. A UV light shows them clearly from several yards away, so you do not need to get close.

Woodpile and stacked pots against a block wall creating scorpion harborage in an Arizona yard — Anything stacked against the wall gives scorpions a second roof.

Mistakes that make the wall worse

These common habits keep the problem going:

Stacking firewood or leftover block against the wall
Letting ivy or vines climb it
Running drip lines along the base
Plugging weep holes, which need to breathe
Assuming one quiet week means the job is done
Tearing the wall open in winter without expecting a cluster

Earthwork matters as well. Landscaping changes can move scorpions, since they often relocate when disturbed by building or yard work. If you are planning new gravel or a new wall, expect some movement toward the house for a while.

UV flashlight beam on a block wall at night revealing glowing scorpions in a low desert yard — A warm-night UV survey shows which stretch of wall is active.

How Kai looks at a block wall

Kai's view is that the wall is rarely the whole story. The questions worth answering are how the wall connects to the house, where water sits, and what the yard is offering scorpions to eat and hide under. If scorpions are reaching the house, the door and weep work often matters more than another pass along the block.

Customers say he treats inside and out and explains how to prevent problems, which suits this job well, since most of the prevention ends up with the homeowner. If you are not sure which kind you are seeing, the page on bark scorpion control covers identification. Sealing is something to raise on the phone. Scope depends on the property, and Kai will tell you if he takes it on.

Tired of seeing them on the wall after dark? Call (209) 563-1650 and describe the yard.

Sources

About the author

Kai Horner owns and runs Kekoa Pest Control, a family-owned pest and weed control business based in Tempe, AZ, serving the East Valley since 2022. More about Kai