by David Moore
Manager of Technical Services and Board Certified Entomologist
with contributions by Eric Smith, PhD, BCE
Good outdoor preventative pest management is the first step of indoor pest management. The best way to reduce the number of pests requiring control indoors is to intercept and control potential invading outdoor pest species before they can come inside. The second step is to physically prevent their entry by sealing routes of entry such as holes in exterior walls, closing gaps under doors, screening windows and vents, etc.
Good outdoor preventative pest management reduces the number of unwanted pests indoors. This in turn reduces the amount of time required to inspect and find their entry point(s) and will probably reduce the amount of pesticide that may be required to solve your problem.
Ecological considerations of what invading pests need to survive:
- Moisture. With the exception of moths and predator groups such as ants, ground beetles, centipedes, and spiders, almost all invaders have a major problem with losing water through their exoskeleton. Therefore, they are all found in areas of high humidity which surround buildings such as mulched shrubbery and plant beds, and under decks and porches, and among dense ground cover such as ivy. The predators get their moisture from the critters they feed on, and moths get their moisture from flowers or droplets of water.
- Food. As immatures and as adults (except the moths, flies, some ants, and predators), these invading pests feed primarily on decaying organic matter, fungi, and bacteria which is found in areas of high moisture. The moths feed primarily on flower nectar and flies feed on a wide variety of organic matter and liquids.
- Activity periods. These invading pests are active primarily from dusk until sunrise because this is when the relative humidity in the air is highest, which helps reduce their water loss. Ants which feed on plant recreations or honeydew are also active during the daytime. The ground beetles and moths are usually attracted to lights at night.
- Resource or reservoir sites. These high moisture, high organic matter containing areas typically function as breeding and population build-up areas. From these areas which are highly favorable for their survival, they then enter buildings when the area becomes overpopulated and/or environmental conditions become unfavorable (too wet or too dry) for their survival.
What the homeowner can and should do:
Sanitation and exclusion are key. The objective is to remove or reduce conditions that are conducive to pests such as favorable harborage near the building, to create a hostile or dry environment immediately around the building, to reduce other factors which attract pests to the building, and to physically prevent pest entry.
- Reduce or remove high-moisture harborage.
- Lawn. Keep the grass cut short and keep the thatch build up to a minimum.
- Mulch. It’s best if this is kept to a minimum thickness (2″ or less) and that cypress or other mulch which is resistant to decay is used.
- There should be a gap of 12-18″ between the mulch and foundation, see vegetation gap below.
- Leaves and other debris. All debris should be removed from around the base of the building on a timely basis.
- Firewood should be stacked up off the ground, the top covered, and be located at least several feet (10-20) away from the building.
- Create a hostile or dry environment next to the building.
- Grade of lot. The soil should drop or decrease at least 6″ in elevation the first 10 feet from the foundation wall to move rain away from the foundation.
- Vegetation gap. It’s best if there is at least a one foot gap between the foundation and the nearest vegetation to allow air to circulate, which reduces moisture. For commercial buildings, this gap should be at least 18″ wide and paved with gravel, blacktop, or cement. This air gap will also prolong the life of the masonry and any siding.
- Trees and shrubs. It’s best that there are gaps between the trees and shrubs which allows sunlight to reach the ground. Also, no tree branches should overhang the building. Insects and rodents use these as a highway onto buildings.
- Reduce attraction factors.
- Flowering plants. Do not plant flowering trees (especially cherry, crab apple, and pear) and flowering shrubs (especially Spiraea species) near the building. They are very attractive to carpet beetles, tent caterpillars, and other insects.
- Gutters and downspouts. These should be functional and in good repair. They should empty away from the building to reduce moisture build up, pest attraction, and possible wood decay.
- Patios, porches, decks, sidewalks, and driveways. These should all slope away from the building to reduce moisture accumulation around the building.
- Compost piles. These should be located as far away from the building as possible. Proper management helps reduce their attractiveness; e.g., add in a layer of soil, etc. periodically.
- Garbage cans, dumpsters, trash compactors. These should always be tight sealing and periodically cleaned. They should be emptied on a timely basis to reduce their attractiveness; at least once a week if flies are a problem because flies can go from egg to adult in 7-10 days in the summer.
- They should be located away from entrance doors to reduce fly entry.
- Lighting. Change white bulbs to yellow and change mercury vapor to sodium vapor, which are much less attractive to insects. If possible, move the light fixtures off the building but so that they shine onto the building which reduces the building’s attractiveness. Also, do not locate lights directly above entrance doors; best to mount them on the door hinge side.
- Physically prevent pest entry.
- Doors should be tight fitting so as not to allow light to escape to the outside at night.
- Doors should have self-closing devices on them where practical, especially on screen doors if present.
- Windows should be tight fitting and securely screened if they can be opened.
- Door and window frames should be completely caulked.
- All holes through the exterior walls for utilities, etc., should be sealed.
- The junction of facia boards and siding should be tight fitting or caulked.
- Attic and soffit vents should be screened.
Realize that the above list has many things that can and should be done to reduce the attractiveness of the area around a building to pests and to prevent their entry. Understand that it is not necessary that all or even most of these be done to have a successful pest management program, but each and everyone can contribute, depending on the pest(s) involved.
Now you have the knowledge so that you can effectively help contribute to a successful preventative pest management program for your home or commercial establishment.
Call a pest management professional for assistance in identifying and determining which of the above items are most important to help solve your pest management problem.