Phoenix Pest Calendar: What Is Active Each Month in the Salt River Valley

What pests are active in Phoenix each month?

Roof rats lead in January and February, bark scorpions and bee swarms return in March, swarms peak in May and June, the monsoon from June 15 to September 30 drives termites, roaches and stings, and activity eases from October. The table below gives each stretch of the year and where the information comes from.

Phoenix does not have four tidy seasons. It has a long, extremely hot summer, a short monsoon on top of it, and a mild winter that suits some pests better than the heat does. The pests below are the ones that move with that rhythm in the Salt River Valley.

Where a month has little sourced information, the table says so. A calendar that fills every box with confident detail would be guessing for November and December, and you would not be able to tell which boxes to trust.

What happens in January and February?

Roof rat activity rises in cooler weather, and Maricopa County urges residents to pick ripening citrus before it falls or sits on the tree. Bark scorpion activity is low in the low desert at this time of year. These are the months to deal with fruit trees, eaves and roof vents.

Winter is the quiet season for scorpions and the active season for rodents. The county's advice, as reported by KTAR, is to pick ripe fruit promptly, seal gaps under eaves and screen roof vents. Those jobs belong to the cooler months because that is when the rats are moving.

If you live in or near Arcadia, a citrus yard is a food supply that stays on the tree for weeks. Our guide to roof rats in Phoenix's citrus belt covers what the county says and what to look for, and the roof rat control page explains how a licensed company approaches it.

This is also the season for a quiet check of the roofline. Sealing a gap in January is easier than finding out in April that something has been using it.

What changes in March and April?

Bark scorpions become active again from about March in the low desert, Africanized bee swarm season begins around mid-March in a normal year, and SRP flood irrigation starts its summer schedule in April. Spring is the best moment to look at walls, rock beds and irrigation boxes before the heat arrives.

March is the month the calendar turns. Scorpions that were quiet through the winter begin to move, and bee swarms start appearing. Neither shows up on a fixed date. The start varies from year to year, which is why this guide uses months and ranges and not exact days.

April brings a second change that is easy to overlook. Salt River Project delivers flood irrigation about every 14 days from April to September to the roughly 20,000 metro Phoenix properties that receive it, and Arcadia is among the sourced examples. Water on the ground is a draw for scorpions and for the insects they eat, and leaking irrigation is worth fixing.

Spring is the right time to read our guide on bark scorpions and block walls and to walk your own wall line. If you have a rock yard or hollow-block walls, a visit before the peak lands earlier than a visit after the first sting.

Why are May and June so busy for bees and termites?

May and June are the peak honey bee swarm months in Arizona, drywood termite swarmers fly from June to August on sunny days, and the monsoon officially begins June 15. Several different problems arrive at once, and each needs a different kind of company or visit.

Bee swarms are the loudest event of the season. Africanized honey bees are widespread in Arizona, and most swarms come in May and June. In peak weeks, one ABC15 report said removal calls can jump from 5 to 10 a day to 30 to 60. Our guide to bee swarms in Phoenix explains what to do and what never to do. The short version is to stay back, keep people and pets inside and call.

Drywood termites are a different matter. Dark western drywood termites swarm from June to August on sunny days, not after rain. Finding wings on a windowsill in June does not mean the monsoon termites have arrived, and the two kinds of swarm point to different problems. Our guide to termite swarms after monsoon rain separates them.

June 15 is the official start of monsoon season as defined by the National Weather Service, though the first storm rarely arrives on cue.

What does the monsoon bring from July to September?

The monsoon brings desert subterranean termite swarms after rain, the peak of bark scorpion stings, American cockroaches coming up sewers and pipes, more ant and roach calls, and mosquitoes breeding in standing water. Maricopa County sets traps weekly and fogs around positive ones. It is the busiest quarter of the year.

Rain does two things to Phoenix pests. It forces animals out of hiding, so scorpions look for dry places, including inside homes, and roaches and ants follow. It also triggers breeding and swarming, so termites and mosquitoes appear.

On the public-health side, Maricopa County Environmental Services sets more than 800 mosquito traps a week, tests for West Nile and St. Louis encephalitis, and fogs a one-square-mile area around a positive trap. What you control is standing water in pots, buckets and toys.

Our guide to monsoon pests in Phoenix goes into this in detail, and the service pages for scorpion control, cockroach control and termite control cover the main calls. The pattern for homeowners is the same: the visit that helps most is the one booked before the first big storm.

What do October, November and December look like?

October winds the year down: the monsoon season ended September 30, bees can still swarm until late October in a normal year, and scorpions remain active. By November, SRP irrigation moves to its winter schedule and roof rats become the pest to watch. Little sourced pest data exists for November and December.

October is a tail, not a cliff. Scorpions are still active through the month, and bee season can run to late October, so a swarm in the first weeks of October is normal. The fall is a good time to review what the summer showed you.

From October to March, SRP flood irrigation drops to about every 28 days. That is a slower rhythm for the yards that get it, and it coincides with the return of roof rats in cooler weather. Winter fruit may draw them, but that link is an inference and not a measured fact, so treat it as a reason to check, not as a prediction.

If you are planning ahead, this is the season to book the inspection and sealing work you put off in summer, so the next March starts on a clean footing.

How should you plan your year around this calendar?

Do the preventive jobs a season early: fruit and roofline in winter, walls, rock and irrigation in spring, bee and swarm awareness in May and June, and a pre-monsoon visit before June 15. The table below pairs each season with the job that belongs to it and the page that explains it.

The point of a calendar is to move work earlier. Most Phoenix pest problems are cheaper and calmer to deal with before the peak than during it, and a company is usually easier to schedule in April than in the middle of a swarm week.

None of the jobs below needs a specific price here. The price is explained and approved before work starts, and the pest control cost guide shows what drives it.