Fumigants are volatile chemicals, their vapours entering the insect by
inhalation or throughthe bodysurface. Fumigation is usedin dried foodstuffs,
buildings and ships. They are typically applied as a gas; however, PH 3 is usedin
a solidstateand when contacted by atmosphericmoisture, hydrogenphosphide
gas (PH 3 ) is released to kill its targetinsect. Fumigantsare highlyeffectiveand
haveno residual propertiesafterventilation.
Aerosols are effective against exposed adults in processing plants and
warehouses. Aerosols are effective becausetheytake the insecticidein wateror
oil-based emulsions and the aerosolgeneratorcreates a mistor fog of fine
particles of liquid. The fine particles can remain suspendedin air for several
hours, untiltheymeet an insect:the particle willthen stickon the insect,
eventually penetrating its waxyouter surface, then enterthe bodyand poisonthe
insect. The benefitof this treatment is that you can treatlargeareas through the
ULV(ultra low volume)concept and utilizenatural air currentsin a building or
spaceto carrythe insecticidedroplets to the insects.Typically dropletsizesof 1
to 15m are most effective; larger particle sizesfall out of the atmospheretoo
quicklyand are less effective.Thistreatmentis effectiveagainstflyinginsects
and relatively ineffective againstlarvalstagesin foodmaterial or crawling
insects in cracksand crevices. The disadvantagewithaerosols is that theytreat
the infestation activity on the surface and needto be reappliedfrequentlyto
effectcontrol. Largefacilities today haveinstalledaerosolsystemsthat are
designedto deliverspecificdropletsize insecticidesthroughstrategicallyplaced
application nozzles that guarantee complete coverage of the space being
protected.
Residual insecticides utilize an insecticideapplied in sucha waythatit
remainsactivefor a considerable periodof time.Dusts, sprays,and lacquersare
usedto deliverlong-lasting insecticideswithwhichan insectmaymakecontact
withover time.A numberof contactinsecticides,whichare activeagainsta
widespectrumof storedproduct,are in commonuse in grainand othercom-
modities. Methoprene is a juvenoid, witha recommended doseof 2±4 mg/kg.
Pirimiphos-methyl (Actellic) organophosphores dosage: 4±10 mg/kg;
Deltamethrin,a synthetic pyrethroid,0.5±2mg/kg; against R. dominica and
otherstored productinsects a mixture of pirimiphos-methyl4±8 mg/kgand
deltamethrin 0.3±0.5mg/kgis recommended.The chemicals can be applied to
the graineitherby pumpsprayers or by gravity techniquesduringthe transfer of
the grainto the bin.
Physicalmeasures
Theseare environmentallysafe measures whichshouldbe usedas a substituteto
the chemical methodsif possible.
Entoleter
Thisis a device that has beenaroundfor a longtime. The entoleteris usedin
flourmills and flourreceiving plantsas a mechanical means of destroying
insects. Flourthat is transferred to the entoleteris blowninto the machineand
Improvingthe control of insects in foodprocessing 421