Psocid

Importance

There are about 2,200 species of psocids worldwide with about 270 species known from the North America. Although the psocids are sometimes called lice, none of them is parasitic. They are rarely damaging inside buildings; however, in large infestations:

• They may cause significant damage to delicate materials such as books and furs.
• They may cause food spoilage to bagged nuts, chocolate, fishmeal, milk powder, oil seeds, processed cereals, yeast and salami.
• They can become a nuisance due to their presence.

Food Sources

Psocids feed on different materials such as thatch, stored food stocks, museum exhibits, molds/ fungi, organic matters, grains, cereals, paste, insect fragments, and other starchy material, including glue from book- bindings.

Habitats

Psocids can be found in outdoor and indoor environments. They prefer inhibiting damp, warm, undisturbed places.

Outdoor

Found on bark, leaf surfaces, leaf litter, in bird and mammal nests or in caves.

Indoor

Occur in warehouses, food manufacturing, granaries, museums and residences places

• In storage pallets and packaging of flour, rugs, paper, straw matting, dried plants, dried milk etc.
• In cracks of dusty windowsills and shelves
• In glass, pharmaceutical, bottling, canning, insect light traps (ILTs) and insect collections
• In improperly stored wooden pallets with mold
• In wall voids of new construction “mold growth before the plaster or sheetrock walls have dried out”

Biology

• Psocids undergo simple metamorphosis
• The females of some species of psocids can reproduce without fertilization
• Each female deposits singly or small batches of sticky, oval, and covered with a silken web or debris eggs on food sources. Females lay in average from 20-50 eggs/lifetime. Eggs deposit average depends on the time of the year.
  • At 50-87 °F (Oct.- Jan.) , eggs deposit average 20
  • At 60-90 °F (June- Aug.), eggs deposit average more than 50
• Eggs hatch in one-three weeks
• Depending on optimal conditions (temperature, humidity and food availability), nymph will go through 3-8 molts in about two –eight weeks.
• Adults will live normally from one to six months.

Management

Long-term management of psocids only can be achieved by reducing the moisture levels, sealing cracks and crevices where psocids may be entering or hiding, applying “first in, first out” food management policy, continuing inspecting and monitoring practices.

Non-Chemical Methods

• Inspecting & Monitoring
  • Applying a regular visual inspection of susceptible materials using powerful flashlight and magnifying lens is necessary and recommended.
  • Inspecting for conditions favor to psocid infestations such as the presence of mold, fungi, high humidity or moisture is a good way to detect the infestations.
  • Sticky traps may not be attractive to psocids but they can be used in heavy infestations.
• Physical Management Methods
  • Heat or cold treatments
    • Dry goods should be treated by placing them in a deep freeze for 24 hours (enclose the products in a plastic bag)
    • Heat treatments at 126°F for 8-10 hours can be used to manage psocids “egg is the most heat tolerant stage”
      • If applicable, infested materials can be exposed directly to a hot sun for one to two days
  • Reduce the relative humidity to below 45- 50%
  • Removal of pest life stages
    • Dry cleaning and vacuuming especially cracks and crevices
    • Discard infested materials outside the building

Prevention

• Keep food storage areas cool, dry and well ventilated
  • Reduce relative humidity to below 45- 50%; a dehumidifier, fan or airing out a room help in reducing moisture
  • Eliminate condensation and repair any moisture problems
  • Store boxes, bags, books, and papers off the floor to minimize exposure to dampness
• Check all new packets of food and place any vulnerable foods in sealed and washable containers
• Use opened packets of food as soon as possible
• Eliminating Harborage Sites
  • Seal all potential exterior entry points and all interior hiding areas in cracks and crevices in walls, between panels, where two units are jointed together and other similar locations
  • Remove leaf and grass litte
• Varnish or paint unfinished (bare) edges to food storage cabinets “mold inhabiting interior paints”
• Immediately remove spilt food and prevent food debris accumulations
• Regular cleaning of the cabinets/ cupboards; be careful not to make the chipboard wet to avoid mold growth

Chemical Methods

The use of pesticides for psocids management is of limited value and not needed if strict sanitation is practiced for the following reasons:

• Routine fumigations of warehouses and storage facilities with methyl bromide have failed to control psocids (Ho and Winks, 1995).
• The rapid development of resistance to chemical and physical treatments by the psocids has also been reported (Santoso et al., 1996; Wang and Zhao, 2003).

In heavy infestations, insecticide applications will not provide a long-term control especially on concrete (porous surface). If pesticide applications are needed and justified as the last resort:

• Use a combination of residual insecticides with flushing agent
• Weekly residual insecticides treatments may be required in heavy infestations
• Remember to read the label before treatment and follow precautionary measures
• Application methods:
  • Indoor Treatment
    • Treat wall and ceiling voids, attics not used for storage, and cracks and crevices around baseboards, door and window framing and other infested habitats
  • Outdoor Treatment
    • Treat structure foundations & perimeter, rotting logs, grass piles, tree bark, around door & window sills

Precautionary Measures

• During the treatment, no people, food, or pets should be present in the room to be treated. Aquatic tanks should be covered and unplugged.
• Do not enter the treated room for FOUR hours after the treatment

Post Treatment Information

• Psocids MAY continue to be seen after treatment until the feeding and breeding sources are destroyed
• Continuing inspecting and monitoring practices should be established on a weekly basis

References

• Ho SH, Winks RG. 1995. The response of Liposcelis bostrychophila Badonnel and L. entomophila (Enderlein) (Psocoptera) to phosphine. Journal of Stored Products Research. 31:191–197.
• Santoso T, Dharmaputra OS, Halid H, Hodges RJ. 1996. Pest management of psocids in milled rice stores in the humid tropics. International Journal of Pest Management.42:189–197.
• Wang JJ, Zhao ZM. 2003. Accumulation and utilization of triacylglycerol and polysaccharides in Liposcelis bostrychophila (Psocoptera, Liposcelididae) selected for resistance to carbon dioxide. Journal of Applied Entomology.127:107–117.