Common stored product pests

There are all kinds of insects and parasites that can end up in food, cabinets, pantries and all over your place of business.

These pests bore into food like grain, cereal, fruits, bread and more. Some of them even spend most of their lives inside a single bean. What these insects do is eat the stored product and leave behind holes and damage that immediately indicates the product is no good.

Here are some of the common stored product pests that are typically found in the US:

Confused Flour Beetle

(Tribolium confusum)

Confused Flour Beetle Image

Appearance

Adults are reddish-brown. Larvae are brownish-white or yellowish-white. The end of the non-movable last body segment is dark.

Biology

  • Females choose a nice spot in bagged foods to lay their 300-500 clear-white, sticky eggs – 2-3 per day.
  • 5-12 days later the eggs hatch, and depending on temperature, the complete life cycle takes 7 weeks to 3 or more months.
  • 4-5 generations can take place each year in heated storage facilities and processing plants.

Habits

  • The beetle moved from its balmy home in Africa to cooler climates around the world. They are more common in the northern states in the U.S.
  • These beetles like to feed on snuff tobacco, drugs, and even poison rodent bait as well as  damaged grain and grain products, peas and beans, shelled nuts, dried fruit, chocolate and spices (such as cayenne).
  • Other than being a nuisance all on their own, they make our food stinky and bad-tasting.

Drugstore Beetle

(Stegobium paniceum)

Biscuit Beetle Stegobium Paniceum

Appearance

  • Mature larvae are white. Adults are reddish to dull brown.
  • The body is made up of a series of small basal segments followed by three much larger elongated segments that make up the outer half of the antennae.
  • Pits on wing covers are in long rows.
  • Mature larvae may be mistaken for very tiny elbow macaroni, as they are C-shaped.
  • These are covered in short hairs and have well-developed legs with four segments.

Biology

  • Females lay oval, whitish eggs in food.
  • They hatch and go through 4-6 stages over the next 4-5 days in a silk cocoon with food particles (a snack) woven into it.
  • A complete life cycle takes about 7 months, with 1-4 generations per year, depending on temperature.

Habits

  • Attracted to light and can be found in light fixtures.
  • Feeds on museum specimens, leather, books and manuscripts.
  • Its larvae has strong jaws that easily bore through packaging materials of stored goods.
  • The name may have come from their being a pest of stored herbs in apothecaries, or early 'drugstores'.

Indian Meal Moth

(Plodia Interpunctella)

Indian Meal Moth

Appearance

  • Each forewing is coppery red on the outer half, with a creamy white basal half. The head is yellowish to reddish-brown.
  • Mature larvae can be even more colorful (including green, pink, or brown) depending on what they eat. Usually, though, they are dirty white.

Biology

  • Females lay their eggs in food supplies, either singly or in small groups during a 1-18 day period.
  • These then make a webbed, tunnel-like case with silk and insect excrement.
  • The length of larval stages (13-288 days) depends on temperature and food availability.
  • Last instar (stage) larvae leave their food to scout out a good place to develop into pupae.
  • The complete life cycle takes 25-135 days, with 4-6 generations per year.

Habits

  • Prefer feeding on dried foods such as fruit, nuts, seeds, crackers, powdered milk, dried red peppers, cereals and other grains as well as chocolate and candy.
  • These can also eat pet food, e.g. dry dog food to bird seed.
  • Their webbing can spoil food.

Merchant Grain Beetle

(Oryzaephilus mercator)

Merchant Grain Beetle Oryzaephilus Mercator

Appearance

Adults are typically a dark brown or dark reddish-brown. The larvae are a yellowish-white.

Biology

  • The female lays 22-190 white, shiny eggs either singly or in small clusters in crevices in food material over several months.
  • The eggs hatch in a few days.
  • The life cycle (egg to egg) typically requires 30-40 days, but may require over a year. Adults usually live several months.

Habits

  • The merchant grain beetle can be found worldwide and easily tolerates cooler climates.
  • Adults can fly and are attracted to light. And with those saw-like teeth, they can chew into unopened paper or cardboard boxes, through cellophane, plastic, and foil wrapped packages.
  • Its flat body form lets it crawl through very small cracks and into imperfectly sealed packages.
  • It is commonly found in oilseed products like nuts and cereal products, rolled oats, rice flour, cake mixes, macaroni, and cookies.

Red flour beetle

(Tribolium castaneum)

red-flour-beetle-bug-book

Appearance

  • Adults are about 1/8" (3-4 mm) long and reddish-brown. Larvae are white and tinged with yellow.
  • Their antennae have an abrupt, 3 segmented club. The wings are functional, but they typically fly only short distances.
  • Full grown larvae are about 1/8"- 1/4"(4-5mm) long, hard-bodied, cylindrical, and wiry in appearance.

Biology

  • The red flour beetle female deposits about 300-500 clear, white, sticky eggs on or among food materials in cracks, in bags, or through the mesh of sacks containing food.
  • The female lays 2-3 eggs per day, and lives for 2-3 years. The eggs hatch in 5-12 days into brownish-white larvae and reach maturity in about 30 days under optimal conditions.
  • In heated storage facilities and processing plants, there are 4 or 5 generations annually.

Habits

  • Red flour beetles are known as "bran bugs", since they primarily attack milled grain products, such as flour and cereals.
  • Both adults and larvae feed on grain dust and broken kernels, but not the undamaged whole grain kernels.
  • These also survive on peas, nuts, dried fruits, spices, milk chocolate, drugs, snuff, cayenne pepper, and herbarium, insect, and other museum specimens.

Rice weevil

(Sitophilus oryzae)

Rice Weevil Image

Appearance

  • Adult is dull reddish-brown; larva is creamy white with a brownish-black head.
  • Has a long anteater-like 'snout' at the front of its head, with a pair of chewing mandibles on top. The male's snout is shorter, wider, and more distinctly punctuated than the female's.
  • Adult's elytra (forewings) usually have four, faint, red to yellow spots, and wings are used for flight. There are deep pits on the thorax that are round or irregular-shaped.
  • The midline of the pronotum (top body plate) is usually puncture-free. Larvae are legless and fairly smooth.
  • There are 7-8, tiny, finger-like sensory projections on the lower mouthpart.

Biology

  • Larvae must raise themselves in their own grain of rice.
  • Females lay eggs in single grains by boring a hole inside. She lays 300-400 eggs in her lifetime, but seldom in winter, as egg laying decreases with temperature.
  • The grain is then sealed off with a gelatinous material after eggs are laid.
  • Larvae go through 3-4 instars (stages) in about 18 days, then pupate for 6 days.
  • Adults aren't ready to leave the nest just yet, they remain another 3-4 days to ensure they are hardened and mature. Life span varies; in summer it can be as short as 32 days, but adults can live for 3-6 months.

Habits

  • Their diet mainly consists of raw food, such as, corn, wheat, rice, rye, buckwheat, cereals, beans, nuts, cotton, grapes, apples and pears.
  • They are believed to have originated from India, where there is plenty of rice. They are now all over the world, especially warm climates. In the U.S., they are common in field and stored grains.

Sawtoothed grain beetle

(Oryzaephilus surinamensis)

Saw Toothed Grain Beetle Image

Appearance

  • Adult is light to dark brown; mature larvae is yellowish-white.
  • These have a row of six, saw-like projections along each side of the prothorax (first segment of the thorax).
  • Their bodies are long, narrow, and flattened.
  • Mature larvae are long and fairly smooth, with 3 segmented antennae (second segment is longest, third is very small).

Biology

  • These thrive in warm temperatures (86-95 degrees F) and high relative humidity (70% plus).
  • Females find a crevice in food to lay their eggs in, either individually or in clusters.
  • Egg laying occurs during a 2-5 month period, and females can lay up to 285 eggs.
  • Eggs hatch 3-17 days later, depending on temperature.
  • Larvae undergo 3 molts, and make a cocoon, where these grow the saw-like projections.
  • Most adults live 6-10 months, but may live over 3 years.

Habits

  • Feeds on  grains, cereals, bread, pasta, dried meat, dried fruits and nuts, sugar, chocolate and candy, tobacco and drugs.

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