Does Pest Control Still Work in Monsoon Season: What Rain Does to a Barrier Treatment

Pest control still works in monsoon season, but a barrier treatment applied to bare stucco and soil before a 2 inch storm will be partly washed off, and the rain itself pushes crickets, roaches, ants and scorpions toward the house at the same time. The answer is not to skip summer service but to change what is applied, where, and how often, and to use products that bond to surfaces and baits that rain does not remove.

What a Barrier Treatment Is

A perimeter barrier treatment is a residual insecticide applied in a band along the foundation, the base of the block wall, the weep holes, door thresholds, the garage perimeter and the pool pad. Insects that walk across the treated surface pick up the product and die over the following hours or days, and the residue keeps working for weeks. In a mild climate a barrier can last 2 or 3 months. In Arizona it does not, for two reasons: heat and rain.

Heat breaks down most residuals through ultraviolet light and high surface temperatures. A stucco wall at 130 degrees in July degrades a product far faster than the label's lab conditions. Rain does the rest. A hard monsoon downpour hitting the base of a wall and running across the soil physically washes an unbonded product off the surface and out of the top layer of dirt, and the sheet flow across a granite yard carries it away.

What the Monsoon Actually Does

The Arizona monsoon runs from roughly late June through September. The storms are short and violent: an inch or two of rain in an hour, wind that fills the air with dust, and then heat and humidity that lasts for days. For pests this is the busiest time of year.

• Crickets hatch in waves after every storm and move toward the light and the moisture at the house.

• Sewer roaches are flooded out of the sewer and come up drains and cleanouts.

• Ants are flooded out of their nests under pavers and along the foundation and come inside in lines.

• Scorpions are pushed out of low ground and wall cells and go looking for dry, cool shelter, which is your garage and your house.

• Kissing bugs and beetles come to porch lights in numbers on humid nights.

• Mosquitoes breed in every saucer, gutter and low spot within a week.

So the barrier is weakest at exactly the moment the pressure is highest, which is why a quarterly program that was applied in May and not touched again until August fails in July.

What Changes in a Monsoon Program

A summer program in Arizona is built around the rain rather than pretending it will not happen.

1. Product choice. Microencapsulated and suspension concentrate formulations bond to stucco, block and concrete and hold through rain far better than emulsifiable concentrates that sit on the surface. The technician picks the formulation for the season.

1. Placement. Product goes where rain does not reach: into the weep holes, under the eave line, inside the block wall cells, under the pool pump, in the garage door channel and along the interior side of door thresholds. Those spots stay treated when the exposed foundation band has washed.

1. Granular baits. Cricket, ant and roach baits are weather resistant and keep working in the soil and the valve boxes after a storm, and they are reapplied after heavy rain because a new generation hatches with every storm.

1. Interval. Monthly service from June through September on scorpion and desert edge lots, with a re service after any storm that dumps more than an inch, rather than waiting for the next quarterly visit.

1. Drains and cleanouts. Sewer roach work moves to the front of the visit: drain treatment, cleanout cap check, mesh covers, and a reminder to run water in unused traps.

1. Sealing. Door sweeps, weep hole screens and the garage seal matter most in monsoon season because they hold when the chemical does not.

What You Can Do Between Visits

Move drip emitters and sprinkler heads away from the foundation so the soil there dries out between storms. Empty anything holding water after a storm within a few days. Run a gallon of water down every unused drain weekly. Keep the garage door closed and the seal in contact with the floor. Keep patio lights off or switch to yellow bulbs to cut the insect draw. And tell your technician when a storm hit your street hard, because a re service after a big rain is part of a good summer program, not an extra.

When It Becomes a Safety Issue

Monsoon season is when scorpion stings peak, because scorpions are displaced indoors and people are barefoot at night. It is when Africanized bee colonies are largest and most defensive, and when mosquito borne illness risk rises in the Valley. A summer without service on a scorpion lot is a summer with more scorpions inside, and the barrier being washed once is not a reason to let the whole program lapse.

FAQ

Should I cancel service until the rain stops? No. The rain is why summer service exists. Skip the summer and the population that builds through monsoon season is what you are living with in October.

My technician came the day before a storm. Was that wasted? Partly, for anything on bare soil and exposed stucco. Not for what went into the weep holes, the wall cells, the garage and the baits. Ask for a re service if activity jumps after the storm.

Why do I see more bugs right after it rains even with service? Because the storm flushed them out of the ground and the walls at once. A good program has them dying at the door instead of in the living room, and the surge settles within a few days.

If the storms have the crickets and scorpions moving, a residential pest control program from Green Ninja Pest Control is built around the monsoon calendar, with rain resistant placements and re service after the big storms.