Spraying vs. IPM

Editor’s Note: The following was adapted from from Pinto & Associates.

IPM is the best way to control any pest over the long term. But not every job is suited for IPM. Mosquito control is a good example. In our industry, there are two distinct types of mosquito jobs: one is “quick and dirty,” one is management over the long term. As a result, we have two different types of mosquito control.

One Shots.

A “one shot,” for lack of a better term, is when a customer calls on Wednesday because she is having an outdoor function on Saturday evening and the yard is loaded with mosquitoes. Maybe it’s a party or a wedding in a backyard or maybe it’s a church function. No matter the occasion, the customer doesn’t want to hear about Integrated Pest Management, monitoring, source reduction and the like. She wants you to “get rid of those mosquitoes” so guests are not bitten on Saturday. This is a spray job to kill adult mosquitoes, pure and simple (although this customer is a hot prospect for a mosquito IPM program in the future).

There are two effective ways to apply insecticides to kill adult mosquitoes. In traditional “fogging,” you apply an aerosol of very fine insecticide droplets using a thermal fogger or ULV cold aerosol generator. The goal is to spray so that the insecticide contacts the adult mosquitoes.

More commonly in our industry, we apply insecticide treatment of a residual insecticide onto mosquito resting areas, most typically in and on vegetation, where they land on treated surfaces and pick up a lethal dose of insecticide. This is often called a mosquito “barrier treatment.”

The most effective way to apply a barrier treatment into vegetation is with a powered mist blower. However, the application also can be made with a power sprayer, backpack sprayer and even a regular compressed air sprayer. When treating vegetation it is critical to get the insecticide residue onto the underside of leaves where mosquitoes most commonly rest. Mosquito barrier treatments may also include applications to the undersides of decks, porches, and the eaves of buildings.

A wide range of insecticides are suitable for mosquito barrier treatments. Additionally, some EPA-exempt products also have been used for this type of treatment.

One-shot mosquito control jobs are by their nature short term and only partially effective, ranging from 50 to 90 percent reductions depending on the field study. Limitations include: 1) not all mosquito resting areas are treatable or reachable; 2) it is difficult to get complete coverage inside thick vegetation; and 3) mosquitoes can fly in from untreated sites.

Mosquito IPM Programs.

The most effective way to control mosquitoes effectively over the entire mosquito season is through IPM. Briefly, a mosquito IPM program contains these essentials:

Inspections and surveillance. IPM programs for mosquitoes require regular inspections. Mostly, inspectors should be looking for active breeding sites (with mosquito larvae, eggs or pupae) or potential breeding sites, but also for adults (biting counts, traps and resting mosquitoes), potential offsite problems and sensitive areas.

Source reduction. All mosquitoes need water to breed. Long-term effective control usually requires a reduction in the number and attractiveness of mosquito-breeding sites…called “source reduction” in mosquito control work. Source reduction includes removal of mosquito-breeding containers, elimination of standing water, and, in rare cases, modification to bodies of water (elimination of organic debris, ditching and draining).

Vegetation management. An often overlooked component of mosquito IPM, vegetation management, can greatly reduce a site’s attractiveness to mosquitoes. Yards with lots of overgrown vegetation, weeds and brush provide many mosquito resting sites. Customers need to remove weeds and brush, thin ornamental plantings, trim tall grasses, etc., to lessen mosquito pressure.

Larviciding. For standing water that cannot be altered or drained, larvicides are the key control tool. They kill the larvae or they prevent larval development so that biting adults are not produced. They are either applied to standing water, or to a site that will flood later (to control floodwater mosquitoes). The common larvicides are methoprene, B.t.i. and thin surface oils.

Final Thoughts.

Other components of mosquito IPM programs are biological control (primarily mosquito fish), mosquito traps, adulticiding (the last resort, often indicating a program failure somewhere) and, of course, ongoing education and communication with the customer.

The authors are well-known industry consultants and co-owners of Pinto & Associates.