What is in lawn spray
You picked a service. You did not pick the chemical off a menu. Here is how to find out what you actually have.
Step 1. Find out what you have
Most people do not know what is being sprayed on their yard. Nobody walks you through it at the door.
Your applicator can tell you the product and give you the label. Here is a message you can send as-is:
One thing to expect: if you ask whether it is safe, you will probably be told the concerns are overblown. That is an opinion. The product name and the active ingredient are facts. Get those and you can look up the rest yourself.
Whatever they tell you, it is very likely one of the two kinds below.
Step 2. Pyrethroids — Talstar, Demand CS
Active ingredients: bifenthrin, lambda-cyhalothrin, permethrin, deltamethrin.
This is what nearly every residential mosquito service sprays. It coats the leaves and kills what lands on it.
It is broad-spectrum. That is the point of the product, and it is also the problem. It cannot tell a mosquito from a bee.
Step 3. Neonicotinoids — Merit
Active ingredients: imidacloprid, clothianidin, thiamethoxam, dinotefuran.
These show up in grub control and in tree and shrub treatments. They are systemic, which means the plant drinks them up. They end up in the leaves, the flowers, the nectar and the pollen, and they can stay for months.
That is the difference that matters. A pyrethroid is a bad day for whatever is outside when the truck comes. A neonicotinoid turns the plant itself into the problem, for a long time after. If you change one thing, change this one.
What it costs besides the pest
In one 2020 field study, three hours after a single fogging with a pyrethroid, 72.7% of the insects counted were dead. Counts of the insects that were never the target dropped to as little as 5% of what they had been. That study was done in a tropical forest, not a Virginia lawn, so the exact numbers will not carry over. The way it works does.
Bees are not only in the flowers. About seven in ten of our native bee species nest in the ground, and most of the rest nest in hollow stems. Treat the soil and you have treated their houses. Firefly larvae live down there too, for up to two years before they ever light up.
Birds are downstream of all of it. Around 96% of our land birds raise their young on insects, and one pair of Carolina chickadees needs 6,000 to 9,000 caterpillars for a single nest. That number comes from a study done in this metro area. Meanwhile butterfly numbers across the country fell 22% between 2000 and 2020.
What to ask for
You are allowed to ask for a different plan. Best to least:
- No neonicotinoids. The one that lingers, so the one worth cutting first.
- No grub treatment unless there are actually grubs. Most lawns are fine with some. The usual threshold is around ten per square foot. Treating every year without ever counting is the most common way this stuff gets into a yard.
- Nothing sprayed while it is in flower.
- Spot-treat instead of coating everything.
- Fewer rounds per season.
Worth asking too: what else could that money do? Plenty of companies will put it toward soil, seeding or mowing instead, and the lawn is usually better for it.
Sources
- Tan et al. 2020, PeerJ 8:e10033, Persistent mosquito fogging can be detrimental to non-target invertebrates in an urban tropical forest.
- National Pesticide Information Center, Imidacloprid General Fact Sheet.
- Xerces Society, Firefly Threats and Conservation Efforts.
- Narango & Tallamy, Washington DC-metro chickadee study, summary.
- Edwards et al. 2025, Science, Rapid butterfly declines across the United States during the 21st century.
- Michigan State University Extension, Potential impact of mosquito and nuisance insect sprays on pollinators.