insectinfestationin cereal and grainstorageis approximately 10%worldwide.
In developing countries the damagemayaccountfor over40%,depending on
the periodof storage. If we could eliminate this loss,or reduceit significantly,
therewouldbe significant positiveeconomic savings and therewouldbe an
improved chanceto avert famine by utilizingthesecerealsand grains to feed
thosein developing and overpopulated countries.
Insectsusuallycomeinto the warehouse withinfestedgrainor cerealand
comeinto the homewithinfestedpackagedfoods. Under favourableconditions,
insects greatlyincrease theirnumbers and maythencrawlor fly into uninfested
food.Theycan enter throughextremely smallcracksand in somecases can
chewor boredirectlythroughthe wrapperor container.
Insectsnot onlyconsume the commodity, they also contaminatethe foodwith
faeces,webbing, insectfragments, ill-smelling and metabolic product. One must
remember that foods thatare infested after processingand packaging are
considered adulteratedand can no longer be savedthrough fumigationor
cleaning. Onceinfested, the material mustbe destroyed in most cases.This
creates millionsof dollarsof loss for foodprocessors and manufacturers. A good
example of unseen adulteration can be illustratedby the metabolic by-products
of the grainweevil(S. oryzae). In manydevelopingcountries cornis the stable
foodfor the poorerpeople.However, the uric acid producedby the weevilscan
renderthe cornunpalatablebeforeits storage shelf-life. Thisseriously reduces
the valueof the foodas a nutritional sourceand has obviouseconomic impact.
In dry foodthe standard is not morethanfive insectfragmentsin 50g.In
somecountries,keepingthis standard can limitthe export of the commodities.
Thereare attempts to developimmunologicaltests basedon the concentrationof
insect-specific proteinssuchas myosin and othersto standardizethe insect
fragment method.
26.5.3 Ecology of storedproduct pests
Climatehas a significantimpacton insectecology because it can affect insects'
competitorsby favouring or retarding them.The most significanteffect is that
climate can governthe geographical distribution of insects.Someinsects thrive
in a temperate climate, whileothersthrivein a tropicalclimate. For most insects
thereis an optimum climate in whichtheygrowand increase most rapidly.
Effectsof humidity, temperature, food,light,atmospheric gases, andinsect
density
Humidity
Primaryinfesters, suchas the rice and grainweevils,cannotbreed in grainwith
a moisturecontentof 8.0%or less and they will die if restricted to suchgrainfor
food.The flourbeetleand the saw toothedgrainbeetlesare examplesof insects
that can reproduceat low moisturecontent. The flourbeetleand the saw toothed
grainbeetle can survive withmoisture contents down to 6.0% and 1.0%
respectively.
Improvingthe control of insects in foodprocessing 415