How Does Rain Affect Pest Control Treatments?

We get this question quite a lot here at Pest-Ex from concerned residents for obvious reasons.

Needless to say, if you’ve just spent a couple of hundred dollars on having your house or property sprayed for bugs, the last thing you need is to have everything washed away in a big down pour.

In most cases, callers ask us –

• Can a big downpour of rain affect pest control?
• Can you spray pesticides in the rain?
• Does rain wash away pest control?
• Does rat poison dissolve in rain?
• Can you spray insecticide on wet grass?
• Can you do pest control in the rain?
• What happens if it rains after pest control?
• Should we cancel our appointment or not?

Here’s a complete answer to all the questions, along with some key pointers to help you out.

Can a big downpour of rain affect pest control?

If you’ve just had the exterior of your house sprayed and it rains not long afterwards, chances are it won’t affect the treatment whatsoever. There’s 2 reasons for this –

1. Most homes have eaves and guttering that overhang wall edges – so, unless the rain is coming in with 80mph wind gusts and blowing directly against the walls, it’s not going to have any affect.
2. When we treat the exterior of the home or business, we ensure that we don’t spray wet surfaces. This is because the pesticides need to “bind” with the area of which its being applied. In other words – we don’t spray a wet wall. If it’s been raining heavily for hours on end before performing the treatment then it’s probably not a good time to spray. The pesticide needs to bind with the surface for it to take affect.

Can You Spray Pesticides in the Rain?

It’s not recommended to spray pesticides during rain. Most pest control sprays are designed to bond with dry surfaces, such as walls, concrete, or soil. If those surfaces are wet, the pesticide won’t bind effectively, which reduces its effectiveness and may result in the treatment being washed away. Professional pest control technicians will typically avoid spraying in rainy conditions and will reschedule or adjust their approach to ensure the treatment sticks and works as intended.

Does Rain Wash Away Pest Control?

Light rain shortly after pest control won’t usually wash away the treatment, especially if the product has already dried or bonded with the surface. However, heavy or consistent rainfall can potentially reduce the effectiveness of outdoor treatments if the pesticide hasn’t had enough time to set. Modern pest control products are often designed to be rainfast within 15 to 30 minutes, but for best results, it’s ideal to apply them during dry weather.

Does Rat Poison Dissolve in Rain?

Rat poison can dissolve if it’s left exposed to heavy rain, but professional-grade bait is generally weather-resistant. Pest control technicians use tamper-proof bait stations that are sealed and designed to keep moisture out. This protects the bait from dissolving and ensures it remains effective even in outdoor environments. However, homeowners placing rodent bait themselves should be cautious, as DIY options may not offer the same level of rain protection.

Can You Spray Insecticide on Wet Grass?

Spraying insecticide on wet grass isn’t ideal. Most liquid insecticides are designed to adhere to dry blades of grass or soil to ensure maximum absorption and effectiveness. If the grass is wet, the product may not stick properly and could be diluted or washed off, reducing its ability to control pests. Some granular treatments, however, may require watering after application to activate them — but in this case, the product should be applied when the ground is damp, not soaked.

Can You Do Pest Control in the Rain?

Pest control can still be done in the rain, but it depends on the type of treatment and the weather intensity. Indoor treatments are unaffected by rain, so they can go ahead as planned. For outdoor treatments, rain can be a limiting factor. Professionals won’t spray pesticides directly on wet surfaces, as this compromises the effectiveness of the application. However, granular treatments or baiting can still be done during damp conditions if it’s safe and effective to do so.

What Happens If It Rains After Pest Control?

If it rains shortly after pest control has been applied, the outcome depends on how long the treatment has been sitting. If the pesticide had time to dry or settle into the surface, usually within 15 to 30 minutes, then rain shouldn’t impact it much. In fact, some treatments (like granular ant control) benefit from moisture, as it helps the pesticide penetrate deeper into the soil. But if it begins raining immediately after treatment, especially on walls or paved surfaces, you may need a follow-up application.

Should you cancel your appointment?

There will be some exceptions to the rule but for most cases, you won’t need to reschedule your appointment. Obviously if you’re only having the inside of the property treated you won’t need to, but there are a few things you need to be aware of if it’s been raining and you intend on having the outside done.

Firstly, many of the insecticides that we use are insoluble and won’t be washed away by rainfall, however if it’s been raining heavily for days on end, and the weather only looks to be getting worse, then it might be best to reschedule.

Secondly, often when it’s wet and the ground’s soft, most pests, especially ants – they’ll actually come out from the ground because they’re looking to escape the moisture from their nests. This can result in the treatment being more effective because we can not only hit the pests directly but also because the pesticide granules dissolve and are absorbed into the ground, killing off more pests beneath the surface. Infact some treatments require the product to be wet in order for the toxins to be released.

We will often advise the customer gets out into the yard within the first week or two, and water the perimeter of the property in order to activate the pesticides – especially if it’s been considerably dry.

So, for some treatments, if it’s going on wet ground, it’s even more effective.

In Summary

When treating the outside of the home, especially when spraying for spiders etc, we apply a thin film of insecticide spray – usually Bi-Flex Aqua Low Odour – . The product dries within 10 minutes, so if it rains half an hour later, it won’t affect the treatment.

Any treatments performed at ground level, as with granular insecticides, we’re usually treating for ants or cockroaches, especially in the lawns. This type of product works best if it’s wet. Again we’ll usually tell the customer, “If it’s not wet, they’ve got to get out there and give it a bit of a hose.”

So, in summary it really depends on the type of treatment as to whether or not the treatment might need to be rescheduled or affected in any way, but typically this isn’t likely.

Customers should note that no reputable pest control company should be applying pesticides of any sort against wet surfaces. We don’t for the reasons mentioned above. Of course if you have any concerns get in touch with us and we’ll gladly help.

Ready to work with Pest-Ex?

Pest-Ex have been providing pest control services throughout Brisbane, Gold Coast, Tweed Heads and Logan City since 2006. We have performed thousands of pest inspections and have more than 7,000 happy customers.

We’re also –

• Fully insured and licensed
• Our pest controllers are among the most experienced and qualified in the pest control industry
• We only use environmentally friendly products, and are dedicated to providing pest control solutions that are safe for your family and pets
• We are flexible, and can work in residential, commercial and industrial properties

Talk to Pest Ex today for all your pest management and protection services – we look forward to hearing from you!