Structural and Public Health Pests: Occasional Invaders

Pest Management In and Around Structures October 13, 2009 Print Friendly and PDF



Several species of insects and other organisms that are generally not considered serious pests can invade a school building or become established on school grounds. These infrequent visitors may be present in landscaped areas but rarely cause significant issues in schools. Many occasional invaders are drawn to the school by the presence of food in the form of plant feeding insects, leaf litter and trash or sources of moisture from irrigated landscapes or shelter including mulch and other ground cover.

The elimination of conducive conditions that attract these pests is often the most effective approach to managing most occasional invaders. A few occasional invaders are more problematic and may become established indoors for a few days to several weeks.

Physical and mechanical measures may be required to prevent occasional invaders from accessing school buildings.

Table 1 Occasional invaders most likely to be encountered in and around schools.

Common and species name Geographic distribution
Asian lady beetle, Harmonia axyridis Eastern and Midwestern US.
amphipods or scuds, Class Crustacia, Order Amphipoda Throughout the US.
booklice, Liposcelis corrodens Throughout the US.
Boxelder bugs, Boisea trivittata Midwestern and West Central US.
centipedes, Class Chilopoda Throughout the US.
clover mite, Class Arachnida, Order Acari Throughout the US.
crickets, Gryllus spp. Throughout the US.
earwigs, Order Dermaptera Throughout the US.
firebrats Throughout the US.
fleas Throughout the US.
millipedes, Class Diplopoda Throughout the US.
pillbugs and sowbugs, Class Crustacea, Order Isopoda Throughout the US.
slugs and snails, Class Gastropoda Throughout the US.
snakes Throughout the US.
scorpions, Class Arachnida, Order Scorpiones Throughout the US.
silverfish Throughout the US.
springtails, Order Collembola Throughout the US.
stored product moths and beetles Throughout the US.
wood-boring beetles Throughout the US.

Monitoring and inspection for occasional invaders

Occasional invaders are a very diverse group. Although many have common requirements for food, water or shelter, identification of the individual pest is required whenever one of these occasional invaders is found in a school. Any insects or other arthropods that are collected for identification purposes should be placed in a vial instead of plastic bags or tape to preserve key identifying characters.

Adhesive-coated traps are the best monitoring method for most occasional invaders. For some, special traps are available including pheromone traps for stored product moths and beetles.

Inspections for occasional invaders should be focused around doorways and at the exterior perimeter of the building, particularly in areas where vegetation is present close to the structure.

Overwintering occasional invaders such as boxelder bugs or Asian lady beetles enter school buildings in late summer or early autumn through cracks or openings under siding, around flashing, or through weep holes. These insects congregate in voids such as attics or crawlspaces. In the early spring, during periods of warm weather, they may be observed on window ledges or emerge from around light fixtures.

Cultural and physical options for occasional invader management

Cultural, physical and mechanical management options are preferred and include eliminating harborage and excluding outdoor pests from entering buildings. Vegetation should be trimmed so that it does not contact structures and mulch should be raked away from the structure. Moisture around buildings should be reduced by repairing gutter systems, improving site drainage, and ensuring irrigation is directed away from building foundations. Sealing potential entry points such as gaps around pipes and other service penetrations in exterior walls or sealing gaps under doorways are good exclusion techniques for occasional invaders.

Cultural and physical strategies for occasional invaders.

  • Remove individual pests using a vacuum where practical.
  • Adhesive sticky traps can be used to catch individual or small numbers of crawling occasional invaders indoors.
  • Use the least amount of landscaping/irrigation in areas adjacent to the structure and trim vegetation away from buildings to prevent access.
  • Eliminate access points where occasional invaders might enter by sealing cracks and exposed pipe chases, installing door sweeps and screens, repairing door and window seals, etc.
  • Place exterior trash cans and dumpsters away from building entrances.
  • Fix plumbing leaks, improve drainage to prevent water accumulation near the building and clean gutters that hold water.
  • Remove mulch from building foundations to reduce harborage. Do not allow grass clippings or leaf litter to accumulate adjacent to school buildings.
  • Remove debris, clutter or materials that are stored against perimeter walls.
  • Position exterior lighting to avoid attracting crawling and flying insects to building entryways at night. Where possible, use reflective instead of direct lighting.
  • Use sodium vapor or yellow bulbs for exterior lighting to reduce attraction to insects.

Table 2 Commonly used products for physical, cultural or mechanical management of occasional invaders and uses.

Type Example Products Uses
door sweeps and seals Sealeze® Weatherseal Close gap between bottom of door and sill, and between edges of door and frame.
insect monitors, glue boards Catchmaster® Install near potential entry points and harborages to reduce populations/intercept individuals.
window and door screens many Install over windows and doorways.

Pesticide options for occasional invader management

Pesticides are rarely necessary for occasional invaders. However, if established populations are present in exterior perimeter locations and non-chemical methods are unsuccessful in achieving adequate control, crack & crevice or spot applications of a least-toxic product may be required. These treatments should be directed into suspected harborages for the specific pest.

Pesticide treatments are not recommended for overwintering occasional invaders that are present inside a building.

Pesticide options that reduce potential for exposure include insecticide baits in enclosed bait stations. A limited number of effective baits are available for specific occasional invaders. If granular baits are needed, these should be used in tamper resistant bait stations.

Pesticide options that increase potential for exposure for students, staff and other facility users include spray formulations applied to exposed surfaces or broadcast granular products.

Insecticide products for occasional invaders.

Note: The following formulations generally have lower potential for toxicity or exposure.

Active Ingredient Example Products Uses
boric acid Borid® 9444-195 Dust formulation. To reduce exposure hazard, use only in voids that will be sealed after use.
diatomaceous earth Concern® 50932-12 Same as above
disodium octaborate tetrahydrate Boracide® 64405-7 Same as above
orthoboric acid Niban Granular Bait® 64405-2 Provaunt® 352-716 Granular formulations. To reduce exposure hazard, use only in voids that will be sealed after use.
indoxacarb Advion Mole Cricket Bait® 352-651 Same as above
boric acid PT 240 Permadust® 499-384 Pressurized aerosol.

Note: The following products generally have higher potential for toxicity and/or exposure.

Active ingredient Example Products Uses
bifenthrin Talstar® 279-3225 Liquids spray applied to exposed interior or exterior surfaces. Reduce exposure by using these products in cracks and crevices only.
chlorfenapyr Phantom® 241-392 Same as above
cyfluthrin Tempo® SC Ultra 11556-124 Same as above
cypermethrin Demon® EC 100-1004 Same as above
deltamethrin Suspend® SC 432-763 Same as above
lambda cyhalothrin Demand® CS 100-1066 Same as above
rosemary oil Ecoexempt® 2C 67425-20 Same as above

Priorities for occasional invaders.

  • Research
Development of targeted baits.
Efficacy of botanical pesticide products on arthropod occasional invaders.
  • Education
Support materials for PMPs and others on effective baiting strategies for individual occasional invaders.

Additional resources for occasional invader management

Arizona Cooperative Extension. 2004. Scorpions and Mosquitoes. Pest Press. (PDF)
Daar, S., T. Drlik, H. Olkowski and W. Olkowski. 1997. Chapter 13. IPM for scorpions in schools. pp. 103- 105. Chapter 14. IPM for silverfish, firebrats and booklice in schools. pp. 107-110. In IPM for Schools: A How-to Manual. Line drawings, identification, communication, monitoring, management.
University of Maryland Cooperative Extension. 2000. Occasional Invaders. Home & Garden Mimeo #HG8. (PDF)
University of Florida. 2006. Occasional Invaders. A poster of 14 yard- and home-invading creatures, from slugs to centipedes.

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This work is supported by the USDA National Institute of Food and Agriculture, New Technologies for Ag Extension project.