Week 3 - Day 11 - Stored Product Pests

ESSENTIAL READING BEFORE COMMENCEMENT OF COURSE:

Urban Pest Management in Australia: 2004 Edition, UNSW Press, Sydney

by J Gerozisis and P Hadlington - Chapter 12 - Pages 141 to 153.

Chapter 12 – Pests of Stored Foods - problems caused by stored product pests - prevention of pests - inspection and monitoring - non-chemical methods of prevention and control -  food-handling industries - domestic premises - chemical control - surface sprays - space sprays - dusts - direct treatment of stored food materials - grain protectants - fumigation - controlled atmospheres - pheremones

Pest status:

For centuries the problem of storing foodstuffs has been with man and continuous effort is required to prevent the entry of pests to food stores.

Stored products pests are very hardy and can adapt themselves to almost any conditions and locations.  Food products are attacked from time they are in the field until they are consumed.

Pest Species

Rice Weevil

The Rice Weevil is widely distributed and causes enormous grain losses throughout the world annually. They can survive anywhere within a grain mass and multiple very rapidly.  The ability to thrive in warm climates and its vigorous powers of flight make the Rice Weevil the most serious pest of stored grain.

Granary Weevil

The Granary Weevil is similar to the Rice weevil in shape, size, breeding habits and destructiveness.  It is a polished, chestnut brown or blackish insect but is unable to fly.

Angoumois Grain Moth

There are various grain moths, which infest grain but the most destructive is the Angoumois. Many pine size emergence holes are good evidence that this pest has been or is present. Development is slowed by cold weather, but in very warm climates as many as 6 generations are possible annually.Angoumois Grain Moth larvae do not web the grain surface.

Lesser Grain Borer

Flat Grain Beetle

The Flat Grain Beetle is one of the smallest insects commonly found In stored grain. Under favourable conditions this insect may complete it developments from egg to adult in about 5 weeks.

Sawtooth Grain Beetle
From eggs to adult occupies about 4 weeks.  The larvae of the Sawtooth Grain Beetle attack the germ end of the kernel reducing the quality and grade of the grain.

Tropical Warehouse Moth

It is very abundant in warm and tropical countries and is a serious pest of cereal and grain products.  In heavy infestation larvae produce very large quantities of webbing over the surface of the commodity and adjacent parts of the storage structure.

Indian Meal Moth

A small species with a very distinctive colouring.
It is a serious pest of stored grains, milled products, nuts, dried fruit and chocolate.

Confused Flour Beetle

It is incapable of feeding on sound grain, but will attack broken grains and kernel damaged by INTERNAL FEEDERS and consequently help in the final destruction of stored products.

Rust Red Flour Beetle

Serious pest of ground cereal products.  A very strong flier, and usually moves very fast. The breeding and feeding habits of the Confused Flour Beetle and the Rust Red Flour Beetle are very similar and it is impossible to distinguish between their larval stages.

Tobacco Beetle

Affects a wide range of stored commodities.  Despite its common name it is found on many grain farms and homes.  It has been recorded eating crushed oats, pollard, flour and a range of stored seeds.

SECONDARY PESTS
Yellow Mealworm

Found in all sorts of unusual places in addition to such places as breakfast cereals, macaroni and in feed mills and processing plants. The insect can remain in the larval stage for as long as 600 days.

Dark Mealworm

This mealworm is similar in habits to the Yellow Mealworm.  Adults are dull black and about 12mm long.  As the name suggests the larvae is dark brown.

Miscellaneous

Many other pests are found in stored products.  A product, which has become moist or mouldy, is open to infestation by MITES.  The MITES are small, translucent soft-bodies creatures, so minute that a single MITE is just visible to the naked eye.  They contaminate a product with excreta, cast skins from moulting and dead bodies.  Heavy infestations can cause severe tainting, impairing a musty odour to the product.  Skin irritations such as DERMITITIS may result from handling infested commodities and both animals and humans may suffer intestinal disorders from eating infested foods.

Scientific Names

SECONDARY PESTS

DISTINGUISHING FEATURES / IDENTIFYING DIFFERENT SPECIES

Rice Weevil

Metamorphosis            Compete
Egg – Larvae – Pupa            Develops within the kernels
Adult     Eats it way out and emerges to begin the   cycle again.  The higher the grain temperature the quicker this cycle is concluded.
Colour Light reddish or yellow spots.
Size        2.0 – 3.5mm long
 
Angoumois Grain Moth

Metamorphosis            Complete
Eggs                             Laid on the surface of the grain
                                    Normally 40 – 50
Larvae                         Attacks sound kernel gnawing into it and
consuming the contents.
                                    Soft bodied and cannot penetrate below
the surface of the grain.
Pupa                            Within the kernel.  Egg to adult 5 weeks. 

Many pine size emergence holes are good evidence that this pest has been or is present.

Colour                          Buff or yellowish brown
Size                             Wingspread of about 12 – 15 mm.
Development is slowed by cold weather, but in very warm climates as many as 6 generations are possible annually.

Angoumois Grain Moth larvae do not web the grain surface.

Lesser Grain Borer
Metamorphosis            Complete
Adult                            Cylindrical form
                                    Dark brown or black with rough surface
                                    Rain kernels can be reduced to shells
Eggs                             300 to 500 eggs dropped singularly or in clusters
Larvae                         Whitish larvae crawl about, feeding on the flourt producded by the boring of the adults.
May burrow directly into slightly damaged grains.
They complete their growth either within the grain or in the grain dust and transform to pupa and in time to adults.

As with other insects, the higher the grain temperature the quicker the cycle.

Flat Grain Beetle
The Flat Grain Beetle is one of the smallest insects commonly found In stored grain.
Metamorphosis            Complete
Adult                               It is a minute, flattened oblong, reddish brown insect. Elongated antennae about two thirds as long as the body.  It can be found in great  numbers in grain that is in poor condition.
Larvae                            Fond of the germ of wheat and kernels  can be found uninjured except for the   removal of the germ.
Eggs                             Eggs are generally laid loosely in any foodstuffs.
                                                                       
Under favourable conditions this insect may complete it developments from egg to adult in about 5            weeks.

Sawtooth Grain Beetle

Metamorphosis            Complete
Adult                            Dark brown in colour and recognised by the six saw toothed projections on each side of the thorax.
Larvae                         After 3 or 4 days the larvae appears and two weeks elapse before they spin a thin covering in which to pupate.
Eggs                             The female lives from 6 – 10 months and may lay 50 to 2590 eggs, which may be deposited loosely or in any crack or crevice or under or in timber, old bags etc.

From eggs to adult occupies about 4 weeks.  The larvae of the Sawtooth Grain Beetle attack the germ end of the kernel reducing the quality and grade of the grain.

Tropical Warehouse Moth

It is very abundant in warm and tropical countries and is a serious pest of cereal and grain products.  In heavy infestation larvae produce very large quantities of webbing over the surface of the commodity and adjacent parts of the storage structure.
Adult                A small grey moth with a wing span of approx. 15mm
Eggs                 About 250 eggs in the food material
Larvae             Also attack and eat out the germ end of the grain.
Pupa                Occurs in small clusters of grain held together with
                        webbing.
Life Cycle            completed in about 4 weeks under summer conditions

Indian Meal Moth

A small species with a very distinctive colouring.
It is a serious pest of stored grains, milled products, nuts, dried fruit and chocolate.

Metamorphosis            Complete

Adult                            Wing span approx 20mm, Forewings are
characteristically red/brown.
                                    with the inner third creamy white
Larvae                         Attack the germ end of the grain. 
The surface of the grain is matted with web. 
Larvae will mat together grain to form a cocoon in which to pupate.
Eggs                             About 200 eggs and larvae burrow into food mass where they remain until completion of larval growth.  200mm wing span.

SCAVENGERS

Confused Flour Beetle

It is incapable of feeding on sound grain, but will attack broken grains and kernel damaged by INTERNAL FEEDERS and consequently help in the final destruction of stored products.
Metamorphosis            Complete

Adult                            Elongated, shiny reddish brown beetle about 3.5mm long.  The head and thorax are densely pitted and the wing covers ridged lengthwise with punctures sparsely distributed between the ridges.
Eggs                             About 400 deposited loosely and covered with flour or grain or can be covered with a sticky solution.
Larvae                         Yellowish white

Average life of a Confused Flour Beetle is about 12 months.
Usually there are 4 or 5 generations annually. This insect cannot fly

Rust Red Flour Beetle

Serious pest of ground cereal products. 
A very strong flier, and usually moves very fast.

The breeding and feeding habits of the Confused Flour Beetle and the Rust Red Flour Beetle are very similar and it is impossible to distinguish between their larval stages.

obacco Beetle

Affects a wide range of stored commodities.  Despite its common name it is found on many grain farms and homes.  It has been recorded eating crushed oats, pollard, flour and a range of stored seeds.
Metamorphosis            Complete

Adult                            Oval shaped about 2mm to 3mm long. 
Dark brown with a smooth shiny surface. 
Outstretched antennae and head forward
when walking but tucked underneath when
at rest.  Fly strongly and are attracted to light.

Larvae                         Tiny white and hairy C shaped

Pupa                            Found against a firm foundation

Eggs                             Female lays about 100 eggs

SECONDARY PESTS

Yellow Mealworm

Metamorphosis            Complete

Adult                            Shiny dark brown or black and about 12mm long. Adults only live 2 to 3 months.

Larvae                         25mm long, active and are found in all sorts of unusual places in addition to such places as breakfast cereals, macaroni and in feed mills and processing plants. When the larva is fully grown about 25mm long body is elongated, cylindrical and has a harder body wall than larvae of most other stored product pests.  The insect can remain in the larval stage for as long as 600 days.

Eggs                             Each female lays over 250 eggs

Dark Mealworm

This mealworm is similar in habits to the Yellow Mealworm.  Adults are dull black and about 12mm long.  As the name suggests the larvae is dark brown.

Miscellaneous

Many other pests are found in stored products.  A product, which has become moist or mouldy is open to infestation by MITES.  The MITES are small, translucent soft-bodies creatures, so minute that a single MITE is just visible to the naked eye.  They contaminate a product with excreta, cast skins from moulting and dead bodies.  Heavy infestations can cause severe tainting, impairing a musty odour to the product.  Skin irritations such as DERMITITIS may result from handling infested commodities and both animals and humans may suffer intestinal disorders from eating infested foods.

Impact on Food Industries

The control of pests of stored products can present certain difficulties that are peculiar to that type of pest control. Stored product pests often live within food for human consumption. In order to control insects within food, the food must be removed or destroyed, or treated in a way that presents no hazards in its end use.

Primary and Secondary Pest Status

Primary Pests

Attack sound grain and the entire larvae and pupa stages are passed inside the grain

Secondary Pests

Eat broken moist and out of condition grain.  They are also able to eat grain products and other foods.

Common pests found in stored products can be separated into four groups according to their feeding habits:  These can be identified as:

• Internal Feeders

Some insects’ larvae feed entirely within the kernels of grain and are such as the Rice Weevil, the Cranary Weevil and the Angoumois Grain Moth.

• External Feeders

Other insects feed from the outside of the grain even though they may chew through the outer coat and devour the inside.  Examples are lesser Grain Borer and the Flat Grain Beetle.

• Scavengers

• Secondary Pests

Feed only on material which are out of condition, damp and have some mould growth present.  Some of them feed on mould rather than the food product.  An example is the yellow Mealworm.
Feed on grain only after the seed coat has been broken mechanically or by some other insect.  Confused Flour Beetles and Rust Red Flour Beetles are scavengers.

• Secondary Pests

Feed only on material which are out of condition, damp and have some mould growth present.  Some of them feed on mould rather than the food product.  An example is the yellow Mealworm.

Inspection Techniques

• Inspect all likely areas of infestation bearing in mind the habits of the pest concerned.
• Inspect food storage bins on shelves etc. For signs of damage larvae, pupae or silken webbing.
• Inspect the outside of packets or bags for signs of infestation, holes, larvae or webbing.
• Inspect food harbourages in cracks and crevices around shelves or on machinery.
• Inspect any food spillage’s, for signs of infestation.
• Inspect overhead beams and windowsills.
• Inspect any food in rodent stations for pests.
• Collect any small flying beetles and moths and identify them, if they are stored product pests, try to locate source of infestation.

IPM non-chemical methods

MOSITURE AND TEMPERATURE

The two most important factors influencing insects in store grain are moisture content and temperature of the grain.  With Favourable conditions heavy infestations will rapidly build up.

High temperatures above 20 degrees C favour insect development particularly in high humidity above 10%.

Moisture is essential to stored grain insects and any increase in the moisture content of the grain can mean an increase in infestation.

CHARCTERISTICS

All pests of stored grain and products have one or more of the following characteristics:

• The ability to reproduce rapidly.
• The ability to feed on dry grain, with the capability of causing serious infestation.
• The ability to migrate in depths of grain.
• The ability to cause severe and extensive damage to grain by:
•  Rendering it useless by consuming large parts of the whole kernel.

Distribution

Sanitation

In warehouse special sanitation problems may exist.

• To control any of the insects found here, it is absolutely essential that premises be cleared of any loose food materials which may be lodged on the floor, thee walls and the ceiling because this food will provide harbourage for the insects even though the principle infestation may be removed.
• If the management of a warehouse will not clean up this debris, the pest control operator could be well advised not to enter into a control agreement particularly if he must guarantee control of insects.

Food entering the building should be free of infestation; this may mean that the commercial buildings/companies have a stock holding area. Once this has been achieved, the stock can be inspected to see that there are no visible signs of infestation before it is stored with the bulk stock already in the building.

• Areas should be kept free of food accumulations and spillage. These will become infested and the infestation may spread.
• Food, wherever possible, should be stored in insect proof containers. Paper and cardboard packets only give some protection.
• Food should be stored in cool dry conditions. Moisture and heat both encourage infestation.
• Rotation of stock

• Some pests, which must have an environment of high moisture content to survive; such as fruit, vegetables etc, or dried products of high moisture content.
• Moisture content of dry foods can be increased by rain damage in store or during transport, also uptake of moisture from poor flooring.
• During rainy period all food stores must have good exterior drainage to eliminate every possibility of seepage to the store floor areas.
• Increase of moisture will allow the stored products to absorb water vapour, which will if not arrested, promptly and quickly, develop mould formulations.
• Mould effected food would be unfit for human consumption.

CONTROL

There are many very strict regulations governing the
application of pesticides to food containers and contents.

• No pesticide is to be applied to stock or food products, which may contaminate the containers or the food product itself.

• Infestations of food products in store will mostly requirefumigation of the product to eliminate pests.

• Residual sprays can be only applied to walls and floor areas and an aerosol spray used in the air space.

• All treatments must be in accordance with the label requirements.

• Although fumigation is a highly specialised treatment it must always be carried out in conjunction with the applicationof pesticides.

• An infestation may require insecticide spray to the surrounds before or after fumigation.

PREVENTION

• All dust collections of walls, framework and floors should be cleared up and a suitable pesticide applied to these areas.
• Pallets should always be used to store finished products and ample space should be allowed to visually inspect the goods on a regular basis.
• Systematic de-infestation of pallets should be carried out regularly.  Once again, only approved pesticides can be used for this purpose.

Storage Recommendations

Food Warehouses

• Where feasible, cracks and crevices that accumulate grains, dusts etc, should be filled.
• Where feasible goods should be stored away from walls and off the ground, to facilitate more thorough cleaning and inspections.
• New incoming stock should be received in an area remote from the main storage area, and an inspection should be taken out prior to further handling, processing or storage. Material found to be infested should be rejected or fumigated.
• Stock should be rotated as often as possible.
• Equipment or machinery that may accumulate food particles should be cleaned out regularly.
• Where grains are stored, temperature and moisture levels should low, to discourage insect activity.
• Regular and extensive inspection and monitoring (with the use of traps/lures) throughout the entire food handling premises should be on going, to ensure that infestations are not allowed to proceed unchecked.

Habitat Areas

Pests can survive and multiple under a number of variable conditions such as:

• Silos
• Shops
• Farms
• Private houses
• Bakeries

They can live in dried products such as:

• Stored grain
• Dried fruits
• Milled and processed cereal products
• Sweets
• Cheese
• Meat and any other dried food
• Dry ginger
• Dried fish

http://www.ipminstitute.org/school_biblio_buildings.htm#Stored