242 PRINCIPLES OFFOODSANITATION
molasses. They may be applied using a
sprayer or sprinkling can to walls, ceilings, or
floors frequented by flies. Fly bait should be
used regularly during the summer months to
control population growth.
Mechanical Methods
None of the conventional devices to control
insects mechanically is especially effective. Fly
swatters are contaminated and spread insect
carcasses and parts when being used, so they
should not be permitted in food processing,
storage, preparation, or sales areas. A viable
mechanical device for the control of insects is
the air curtain, which not only reduces cold air
loss in a refrigerated facility but also protects
against insect and dust entry into food estab-
lishments. Air curtains can be used for person-
nel doors and entrances large enough for
loading trucks or for the passage of large
equipment. An air curtain supplies a down-
ward-directed fan that sweeps air across the
door opening at rates of up to 125 m^3 /min. Air
curtains are most effective if the area being
protected is under positive air pressure. This
equipment is normally mounted outside and
above the opening to be protected.
Insect Light Traps
One of the safest and most effective meth-
ods of fly control is the use of insect light
traps. This technique does not have the
potential hazard of toxic sprays.
Insect light traps use a high-voltage, low-
amperage current on a conducting grid (Figure
13–1) placed in front of a quasi-ultraviolet
(UV) irradiation source. This light source
attracts the flies toward the light source, where
they are electrocuted. Some light traps contain
a “black light,” which is effective at night, and a
“blue light,” which is effective in the daytime.
Insect light traps in food processing plants
and warehouses should be installed in stages,
as follows:
●Stage 1, interior perimeter:These units
should be placed near shipping and
receiving doors, employee entrances,
and personnel doors that provide access
to the outside or anywhere else that fly-
ing insects may enter. Units should be
placed 3 to 8 m inside the doors, away
from strong air currents and out of traf-
fic areas, where forklifts or other equip-
ment may damage the units.Figure 13–1An insect light trap that attracts flies to the light source, subsequently electrocuting them. (Cour-
tesy of Dan Gilbert Industries Inc.)