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PANTRY PESTS

JAN 16, 2015

Most household pests are all too happy to take advantage of any food that's been left out where they can reach it.  Pantry pests, also known as stored product pests, however, go one step further.  These pests actively infest their favoured foodstuffs, and lay their eggs inside stored food products.  "Pantry pest" is a relatively broad classification, including several species of beetle, weevil, and moth, but the pests are similar in that they tend to favour dry foods, such as grains, cereals, spices, dried fruits, and even pet foods.

Weevils

The most common species of weevil found in York Region are grain weevils and rice weevils.  These insects are small, typically between 3mm and 5mm in length, with narrow bodies and a long snout protruding from the front of their heads.  Both species are reddish-brown in colour, and are most easily distinguished from one another by the fact that adult rice weevils are capable of flight, while adult grain weevils are not.

Both species of weevil prefer whole grains.  Female weevils will bore a small hole into a whole grain kernel, deposit a single grain within, and seal the hole with a gelatinous substance that protects the developing larva.  The development of weevil larvae takes place entirely inside their host grain kernels, which act as both protection and food source for the growing weevil.  As such, it's rare to see immature members of the species in an infested product; the visible individuals will almost always be adult weevils.

Indian Meal Moth

Indian meal moths are small moths, with a body length of 1cm-1.25cm and an average wingspan of between 1.5cm and 2cm.  They are easily mistaken for clothes moths, though the Indian meal moth's wings shade from grey at the base to reddish-brown at the tips, while clothes moths' wings are uniformly grey.  In their larval form, Indian meal moths closely resemble maggots or small worms, averaging 1cm-1.25cm in length.  The larvae are typically off-white, with brown heads.

The Indian meal moth infests dry foods with a grain or vegetable base.  They're most commonly found in flour, cereals, pasta, rice, spices, dried fruits and nuts, and pet foods, though they've been known to infest anything from cocoa powder to breads or packaged biscuits.  The female meal moths will lay their eggs in an appropriate food source, where they will hatch into larvae.  The larvae feed on the contaminated foodstuff, and produce a loose, web-like material that may be mistaken for cobwebs.  Both adult and larval meal moths may be found outside of the contaminated food source, as maturing larvae often pupate in areas other than their point of origin.

Flour Beetles

Flour beetles are small, reddish-brown beetles, between 3mm and 5mm in length, with a body shape like an elongated oval.  In their larval form, they are roughly 5mm in length, and off-white in colour.  Unlike weevils, these insects do not infest whole grains, instead preferring milled or otherwise processed grain products such as flour, cereals, and pet foods.

Both adult and larval flour beetles will feed on the grain products they infest, and the females of the species will deposit her eggs in the grain products as she's eating.  While the eggs themselves are difficult to see, it is possible to spot both the larval and adult forms of the beetles in infested packages, and spying adult beetles in the vicinity of your cupboards also signifies an infestation.  Flour beetles will rarely remain contained to one package, allowing an infestation to spread quickly and damage a significant quantity of food if left unchecked.

Grain Beetles

Both the sawtoothed grain beetle and the merchant grain beetle are common stored food pests.  They are difficult to differentiate from one another by appearance, as they are both small brown beetles, averaging 3mm in length, and produce small, flat larvae that range in colour from white to pale yellow.  Both species of grain beetle feed on milled or processed grains, and will also infest dried fruits, packaged foods such as cereals, flours, and pet foods.

Damage caused by grain beetles is not immediately obvious as coming from an infestation, and the first sign that there's a problem is often the sight of adult grain beetles in or around the infested foodstuff.  Grain beetles feed liberally and breed rapidly, so an infestation that starts in one package may swiftly spread to the rest of the pantry.  In shared living situations, such as apartment buildings, it isn't unheard of for an infestation of grain beetles to spread between units.

Prevention

As with many household pests, it is impossible to completely eliminate any chance of pantry pest infestation. However, there are a few simple steps that can be taken to diminish the chance of finding any unpleasant surprises in your morning cereal:

Make sure to inspect any packaged foods before purchase.  While an intact package is not 100% proof against pantry pests, a broken package is much more likely to be the source of an infestation.  Do not mix new and old packages of food together once you've brought the new package home, as that will only ensure that any pests in one package will swiftly colonize the other.

Whenever possible, store food in air-tight containers, preferably made of glass, metal, or durable plastic.  This will help to prevent any pantry pests you might inadvertently bring in from spreading from their source to other foods, allowing you to contain any potential infestations, and cut down on food waste.  Don't forget to store items such as pet foods or birdseed in appropriate containers as well, as these can frequently become infested.

Clean any containers you use to store foods thoroughly before replacing an old batch of food with a new one.  This will help to eliminate any pests that might have gone unnoticed.

Make sure to clean out your cabinets periodically.  Most pantry pests don't require a large quantity of food, so making sure you take care of any spills before they can become a convenient food source will cut down on pest problems.

Dealing With Pantry Pests

The first step in eliminating an infestation is to discard any infested packages.  If you suspect a package might be infested, you can check by placing it in a clear, sealed bag or jar for up to a month, and checking for any sign of the pests inside the bag.  If you see any of the pest species inside the bag during that month, then it will need to be discarded.  If it remains pest-free at the end of the month, it should be safe.

Once the contaminated foodstuffs are removed, and before you go to the expense of replacing the discarded food, thoroughly vacuum and clean your cupboards.  If you use shelf liners, it's advisable to discard your current set.  You should clean and vacuum inside and around your kitchen appliances as well, as food debris that has fallen beneath your appliances may provide a safe haven for surviving pests.

In the case of a severe infestation, it may be necessary to apply pesticides to eliminate the pests.  If you're having difficulty eliminating pantry pests, or you fear the expense if your infestation recurs, it would be wise to consult a pest control service.  Pantry pests can be difficult to eliminate completely, and a pest control professional can evaluate your situation and help you find the most efficient – and safest – way to deal with the problem and allow you to get back to comfortably using your kitchen.