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Stored Product Pests

  • Stored product pests or pantry pests is the general name given to the group of pests which attack stored grains, cereals and any dry packaged foods.
  • There are a wide range of beetles and several moths that are significant pests of stored foods in commercial and domestic situations.
  • Although they physically damage the food material, their presence is a visible contamination, their body parts and faeces cause allergic reaction and fungal contaminants are often introduced by their activity.

Stored product pests can be split into those than attack stored whole cereals and grains, and those that attach processed grains, cereals and other dried food. However, many species will attack both whole grains and a wide range of dried foods. There are a wide range of beetle pests, a few moth pests and a mite, that causes damage to stored grains and food.

In most cases it is the larval stage that causes most of the damage, although in some of the beetle species they also feed or cause damage to whole grains when they lay their eggs.

The real costs of stored product pests are significant:

  • An estimated 1/4 to 1/3 of the world grain crop is lost each year in storage. (Department of Agriculture and Food, Western Australia)
  • In the U.S. alone, stored product pests can damage, contaminate, or consume as much as 10% of the total food produced; in developing countries, that rate has been estimated at 50% or more. (University of Wisconsin/USDA)

Although they physically damage the food material, their presence is a visible contamination, their body parts and faeces cause allergic reaction and fungal contaminants are often introduced by their activity. They are considered the main pest problem for many food handing and processing businesses.

Both beetles and moths go through complete metamorphosis – hatching from an egg, they go through several larval stages before pupating into an adult.

Some lay their eggs near the food, some on the food and some, like the rice weevil, actually bore into grains and lay their eggs inside the food.

The length of the life-cycle depends on the species and is quicker in warmer temperatures. Under optimal conditions, the life-cycle can be completed in as little as 1-2 months, which means populations can get quickly out of control.

 

Stored product pests are a challenging pest, not only because they will attack a wide range of whole, grains, cereals and processed dry foods, but because of their ability to get inside packets and containers, even after processing.

The larvae of some species (and occasionally the adults) are capable of chewing through plastic bags and the larvae are sometime small enough to crawl around the thread of close screw top containers.

Due to their small size their presence can be hard to detect, until it’s too late and a significant population has developed. Often the adult and larvae will hide within the food source (they don’t like light), sometimes they feed within the grain itself and sometime the larvae protect themselves within webbing which gets coated by the surrounding food material.

Apart from whole grains and cereals, stored product pests will eat a wide range of dry foods including flour, breakfast cereals, rice, biscuits, pasta, spices, nuts, drinking chocolate, coffee, tobacco, dry petfood and even rodent bait.

Stored product pest not only physically damage the food, but their physical presence contaminates the food – bodies, shed skins and faeces.

Not only is physical contamination obviously undesirable in food, they contain allergens that can cause allergic reactions.

In addition, their presence and feeding habits can introduce fungi which further damage and contaminate the food.

Preventing a stored product pest infestation is all about inspection and monitoring

  • Inspect all incoming dry foods (even those in sealed packets)
  • Ensure all opened dry foods are stored in thick plastic or glass containers with a tight fitting top (not a screw top)
  • Monitor for pests, especially pantry moths in residential situations

Sticky traps with a pheromone attractant (which are available at supermarkets and hardware stores) are useful for monitoring and eliminating adult pantry moths.

If you detect a stored product pest infestation, it is important to inspect all your stored dried foods and seal infested foods in a bag before throwing into the outside bin.

Residential situations:

In the residential situation, a pest professional will spend time to find the source of the infestation and then ask you to throw out all infested material.

Once this is done, there isn’t always the need to carry out a spray treatment, but sometimes it makes sense to carry out a residual spray treatment to surfaces in the food storage areas.

Depending on the pest and situation, the pest manager may also suggest you install some monitoring traps so you can detect any new intruders before they can infest your foods.

Commercial situations:

In commercial situations, control of stored product pests is more complicated. The standard process for dealing with stored product pests:

  • Inspection
  • Disposal of infested material
  • Thoroughly vacuum infested area
  • Treatment
  • Monitoring

Treatment may include fumigation of products or large areas and/or treatment of surfaces. The use of pheromones systems to monitor and control populations can also be considered.

Preventation of stored product pests in commercial situations needs an ongoing management plan.