Managing Pests On Complex Surfaces

If insect pests stayed in one place all the time, it would make it easier for pest management professionals to eliminate them. That isn’t the case, however.

Insect pests are foragers by nature and that takes them over a variety of surfaces on the exterior of a structure in search of food, water and shelter. From concrete and gravel to mulch, bare soil and grass, the surfaces surrounding a structure are almost as diverse as the pests that travel across them.

Managing pests on these surfaces is not a one-size fits all approach. Different surfaces require different application techniques and the use of different pesticide formulations including liquid, dust and granular products.

THE CHALLENGE. Complex surfaces – concrete, gravel, and mulch – present a real challenge for PMPs to treat effectively during regular pest maintenance services or in situations where quick knockdown is needed. Why do these surfaces present a greater challenge to PMPs?

“Complex surfaces are not just one type of material and that can make treating them difficult,” says Dr. Phil Koehler of the University of Florida. 

Koehler says the two most challenging complex surfaces to treat are concrete and mulch. Concrete possesses a high pH level and alkaline properties that will break down the active ingredient of a traditional pesticide soon after it is applied.

“It is hard to gain much residual when treating cement and that is why spraying a sidewalk, driveway or cement patio for ants or occasional invaders often proves ineffective,” adds Koehler. 

Mulch, a widely used landscape material around homes across the country, can also lessen the effectiveness of traditional liquid pesticide treatments because of its absorbent properties.

“Organic matter has the tendency to absorb the liquid pesticide and not allow it to reach its intended target – the soil beneath the mulch where pests are more likely to be crawling about and come in contact with the product,” says Koehler. “Mulch is not a friendly surface to treat.”

Dr. Steven Kells of the University of Minnesota says elements within the composition of complex surfaces can make it harder for traditional liquid pesticides to bond to the surface and be available to foraging insects to come into contact with.

“There is chemistry in the lab and chemistry in practice,” says Kells. “If an active ingredient can’t bind to the treated surface it won’t reach the target pest and will likely lead to a failed treatment and a callback for the pest management professional.”

Kells says the challenge in developing chemistries for complex surfaces is to make sure the active ingredient stays available on the surface long enough for the insect to come into contact with it but also successfully transfer to the insect.

“An active ingredient must be able to be picked up by the insect and ingested through grooming and other behaviors to kill the insect,” says Kells. 

Granular products and wettable powders create their own “surface” and can be more accessible to pests but using granules on concrete is not recommended since the product can be easily blown or washed away.

Dusts offer similar properties but can also be limited in their effectiveness depending on the surface being treated.

EXPERT RECOMMENDATIONS. What can pest management professionals do to improve the effectiveness of their complex surface treatments? 

First, invest the time to inspect the surfaces you are being asked to treat, adjust your formulation selection and work the problem from all angles.

Koehler says adjusting your application pattern to treat the areas alongside a cement sidewalk, driveway or patio can be more effective in targeting pests as they cross these areas on their way to the customer’s home. He says the commonly accepted rule of treating 2 ft. up and 2 ft. out can be adjusted by moving mulch to expose soil for treatment and also concentrating on treating the lower walls of a home which have more conducive conditions for insecticide residuals.

“Pests can hide beneath concrete or mulch but the latex paint on the side of a house will hold an active ingredient longer and allow pests to come into contact with it as they forage,” adds Koehler.