Contact vs. residual spray: What's the difference?

Contact vs. residual spray: What's the difference?

Most non-toxic pest control products can be classified in one of two broad categories: contact and residual solutions. While the benefit of contact pest control products is that they kill insects by contact and accordingly tend to work much faster than their residual counterparts, the main advantage of residual pest control products is that they work to kill bugs and prevent infestations over a longer period of time.

Contact sprays and powders

Contact sprays and powders kill by contact. You have to "hit" the bugs for these products to work properly. Contact sprays and powders are meant for killing crawling or flying insects that have been spotted. The ingredients in a contact pest control product do not always need to be ingested by the bug; often, the insect simply needs to come into immediate contact with the spray or powder. This solution (the spray or powder) is often absorbed through the skin of the insect and then acts as a neurological inhibitor, meaning that it suppresses, blocks, or restricts the insect’s nerve activity. It's very effective against insects for two reasons: The first is that because insects are quite small and very simple, they do not have many nerves to disrupt. It takes only a tiny amount of solution to cause nerve disruption, which causes the insect to stop feeding. Once the insect is no longer able to feed, it will die or be eaten by other insects. The second is that insects, unlike larger mammals, are not very good at safely processing chemicals. 

Once a contact spray or powder solution is not being actively used, though, it no longer has a significant effect on the insect. Nonresidual sprays work when you use them and afterword their power is gone.

Residual sprays and powders


Residual sprays and powders kill over time. You don’t even need to see the insect for it to die as a result of an encounter with residual sprays and powders. In fact, the insect doesn’t even have to breathe or swallow the substance. It just has to touch it. There’s no "see, spray, and die" formula here. You simply apply the solution on a surface and the residual product’s active ingredients remain attached to the surface. When pests walk, jump, or crawl through the residual solution, they pick it up on their body parts, such as their legs and antennas.

Residual sprays and powders remain effective for a length of time, depending on the formula (powder, liquid, etc.), the type of surface it is being applied to (soil, wood, carpet, brick, etc.), and the condition of the surface (smooth, wet, greasy, etc.). If the spray is applied outdoors and receives heavy or constant rainfall, its efficacy will be affected.

It’s important to note that all of Dr. Killigan’s products are toxin-free. Insects are known for their ability to develop resistance to pesticides and, currently, there are insects that are resistant to every synthetic chemical insecticide used. It’s always a better idea to stick with Dr. Killigan’s non-toxic and highly effective pest control products, which are always safe for your family and pets when used as directed.

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