Stored Product Pests

Stored product pests infest a wide range of foods including flour, whole grains and seeds, crackers, processed cereals, peas, beans, nuts, dried fruit and spices. Among the common stored product pests are:

Pea Weevil

Larder Beetle

Confused Flour Beetle

Mediterranean Flour Moth

Indian Meal Moth

Drugstore Beetle

Granary Weevil

Saw-toothed Grain Beetle

Yellow Mealworm


Rice Weevil




Correct identification of stored product pests is important in order to know where to apply treatments. Some insects, such as Granary Weevils, spend their entire life cycle in the food, therefore control steps can often be limited to disposing of the infested products.

Others, such as the Mediterranean Flour Moth, leave the food when it is time to pupate. They spin cocoons in the corners of cupboards and cracks, therefore control measures must be planned to take this into account.

Monitoring

Visual Inspections

Storage areas should be inspected carefully for signs of infestations, inside and outside of the packaging or containers. During the inspection, potential problem areas should also be noted. This includes containers of old or stale products, spilled food and hard to clean areas that could provide refuge for insects.

Pheromone Traps

Insect sex pheromones and aggregation pheromones are available for a variety of stored product pests. The pheromones are in lures that can be used in different designs of traps. For stored product moths, the lures are usually placed in delta traps like the one pictured here.

Other trap designs are used for stored product beetles. It should be noted that none of these traps are a means of control but rather just monitoring devices.

Always avoid touching the pheromone lure when setting out the trap because traces of the pheromone can be spread around the area, making the trap ineffective.

Pheromone traps should be placed away from doors and windows to avoid attracting insects from outside and may be hung from the ceiling or placed on a shelf.

Action Decisions

Prevention

For households, once an infestation is cleaned up (see Control below) further infestations can be prevented by:

- freeze grains, flour, dried fruit and other dry foods from bulk food stores in the household freezer for a week before transferring to the cupboard

- store food in insect proof containers of glass or strong plastic with tight fitting lids

- clean kitchen counters and vacuum the insides of cupboards to remove spills and debris

Sanitation

Maintaining clean conditions is the best control. All spills should be cleaned up immediately.

Reduce Humidity

Grains should be stored in a cool dry area. Except for the Mediterranean Flour Moth which can tolerate very dry conditions, most stored product pests are not likely to be a problem in dry conditions, where relative humidity is below 6%.

Barriers

Insect screens should be installed on exhaust fans, windows and other openings to keep flying insects out.

Control

Sanitation measures (discussed above), along with regular visual inspections usually provide sufficient control of stored product pests. In many instances no pesticides will be needed to achieve good control.

Physical Removal

Destroy infested materials. For some species, such as Granary Weevils removing the infested material provides sufficient control as they do not live outside the material.

Heating or Freezing Treatments

Where feasible, extremes of heat or cold can be used to kill insects in infested food. To eliminate an infestation, food should be kept in a freezer long enough to be frozen at the center of the container for at least 4 days.

Heating to 150 degrees Fahrenheit in an oven for 20 minutes also kills insects.

Preferred Pesticides

Sorptive Dusts

Diatomaceous Earth can be applied to cracks and crevices of storage areas where pupae and other stages of some stored product pests hide.

Pyrethrins

Pyrethrins can be applied to equipment motors to kill hiding pests or by ULV machine to storage areas.

Other Pesticides

Other pesticides should not be required for most stored product pests. If required in the case of severe or persistent infestations, pesticides must be chosen with careful attention to label directions. Few pesticide products mention stored product pests on their labels. By law only pesticides labeled for use in the appropriate areas (e.g. food prep and storage ares) and for this group of insects (e.g. stored product pests) can be used.