The short version: May is when the Treasure Valley pest season opens for real. Ant colonies hit full speed, wasp nests grow to fist size, earwigs turn active as irrigation keeps the ground damp, and the first mosquitoes appear near the canals and standing water. The move that matters is managing moisture around the foundation and keeping up your wasp-nest checks, because water is what concentrates pests here and the nests are still small enough to handle.
The pest year has a soft opening in March and April, and then May, when the sprinklers come on and the days get hot, it opens for real. This is the month activity stops being early and quiet and becomes the thing you actually notice: heavier ant trails, obvious wasp traffic, the first mosquito at dusk. Water is the reason, and water is also the lever.
What is active in May and why
The high-desert Treasure Valley is dry country with an irrigation network laced through it, and May is when that water turns on in earnest. Every pest on the calendar responds to it.
Ants hit full speed. May is typically the busiest ant month of the year. The colonies that scouted in March and trailed in April are now foraging at capacity, and indoor sightings spike as workers push in for food and water. The most common household ants in the valley, odorous house ants and pavement ants, are both in high gear. If you caught the colony early with a non-repellent treatment, May is quiet. If not, this is the catch-up month, and ant control that reaches the nest still beats spraying the trail.
Earwigs turn active. The first earwigs stirred in April. In May, with irrigation keeping mulch and flower beds damp, they become genuinely active and start turning up in window wells and along the foundation. Earwigs are a moisture pest above all, which is why the fix is as much about drainage as it is about treatment. The background on them is in earwigs in Idaho.
Mosquitoes begin. The valley's first mosquitoes appear in May, and they cluster where water sits: near the canals, around Lake Lowell, on flood-irrigated ground, and in any bucket, saucer, or clogged gutter in your yard that holds water for more than a few days. Numbers are still low, which makes May the month to cut off breeding sites before they climb.
Wasps and spiders keep building. Wasp nests missed in April grow from golf ball to fist as the queen raises her first workers, and the year's spiders are active outside but still small, which is why nobody notices them in May and everybody notices them in September.
What to do now: moisture and nest checks
May's job is different from April's. April was about removing founding nests and setting the barrier. May is about controlling the two things that decide how loud your summer gets: moisture and wasp nests.
- Take the water away from the foundation Pull mulch and dense plantings back from the wall, fix grading and low spots that stay wet, keep gutters clear, and dump anything holding standing water at least weekly. This one habit thins earwigs, cuts mosquito breeding, and reduces the insect supply that feeds spiders. The full approach is in moisture control to prevent pests.
- Keep checking the eaves Do not stop the nest walks just because April is over. Every couple of weeks, scan eaves, soffits, playsets, and grills and knock down anything growing. A fist-sized May nest is still manageable. The same nest in August is a job for wasp control.
- Hold the barrier If ants are pushing indoors, the exterior barrier may be due for a refresh as heat and watering wear it down. This maintenance is built into the quarterly plan so the barrier stays effective right through the busy stretch.
May sits at the tail of the spring push, and the whole strategy is on the spring pest control guide. The Treasure Valley pest calendar shows how June takes it up another notch.
What is coming in June
May opens the season. June pushes it to peak breeding. Earwigs go from active to swarming irrigated beds, mosquito numbers climb with the heat and the watering, box elder nymphs cluster on their host maples and box elder trees, and wasp traffic on the eaves becomes constant. Everything that turned active in May reproduces hard in June, so the moisture work and nest checks you do now pay off in a quieter summer. We cover it in Treasure Valley pests in June.
The sprinklers are on and the season just opened. Let's set your barrier before June.
Get a Free Quote →May pest questions
Why am I getting earwigs in May in the Treasure Valley?
Irrigation is running now, and it keeps mulch, flower beds, and the ground along your foundation damp. Earwigs breed in that moisture and turn active in May, weeks ahead of their midsummer peak. The lever is moisture, not spray alone: pull mulch back from the wall, fix low spots that stay wet, and the population that feeds on that damp cover thins out.
When does mosquito season start in the Treasure Valley?
Late spring, and May is usually when the first ones show up. They breed in standing water, so the earliest activity clusters near the canals, Lake Lowell, flood-irrigated ground, and any container in your yard that holds water for more than a few days. Numbers climb through June and July, which makes May the month to start dumping standing water before the population builds.
Is May the busiest month for ants in Idaho?
It is often the peak. Colonies that woke in March and organized in April hit full foraging speed in May, so this is when ant trails are heaviest and indoor sightings spike. If you treated the colony in early spring you are in good shape. If you did not, May is the catch-up month, and reaching the nest still beats chasing the trail.
How do I keep wasp nests small in May?
Keep checking and keep knocking them down. In May the nests you missed in April grow from golf ball to fist as the queen raises her first workers. Walk the eaves, soffits, playsets, and grills every couple of weeks and remove what you find. A May nest still has a small crew and is far easier to handle than the same nest in August.
Why do I see more bugs after I start watering in May?
Because water is what concentrates pests in the high desert. The Treasure Valley is dry country with irrigation running through it, so every watered yard becomes an oasis that draws earwigs, ants, and the insects spiders eat. Turning on the sprinklers in May reliably brings a jump in activity at the foundation, which is why moisture management is the season's quiet lever.