Mediterranean flour moth

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The Mediterranean flour moth or mill moth (Ephestia kuehniella) is a moth of the family Pyralidae. It is a common pest of cereal grains, especially flour. This moth is found throughout the world, especially in countries with temperate climates. It is frequently found in warm places with stored grain products, such as flour mills and bakeries, where it can breed year round. It prefers warm temperatures for more rapid development, but can survive in a wide range of temperatures. Flour mills have a particular problem with the Mediterranean flour moth because the caterpillars spin silk that clogs machinery. The most effective pest control strategy for this moth is sanitation of facilities and sealing grain containers to prevent infestation, but some pesticides may also be used.

Description

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Adult moths have pale gray bodies. Their forewings are gray with black zigzag markings while the hindwings are an off-white color. The wingspan is 1.5-2.6 cm. Larvae (caterpillars) are white or pink with black spots and dark heads. Pupae are reddish brown.

Geographic range

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First recorded as a pest species in Germany in 1879, the Mediterranean flour moth was found in several locations across Europe in subsequent years. In the late 19th century, roller flour mills caused the moth to become a more widespread pest. It became a common species in Britain, North America, and Australia by 1980. The Mediterranean flour moth is now found throughout the world, though it is rare in the Far East. Japan is the exception, as the moth is found in flour mills there.

Areas of the world with temperate climates are most likely to have the Mediterranean flour moth as a major pest in flour mills.

Habitat

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Mediterranean flour moths live in stored grain products. They primarily infest flour, but they are also found in a variety of cereal grains.(MN) The moth is a major pest species in flour mills, and it may also be found in bakeries and warehouses, especially in cereal products that have been left undisturbed for an extended period of time. This species particularly enjoys inhabiting flour mills and bakeries due to the heat, which allows it to breed year round.

Food resources

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Caterpillars feed on flour, meal, whole grains, and grain residues. (Penn) Unlike other pest species of moths, E. kuehniella is almost always found in cereal grain products and not other stored foods such as dried fruit. (Jacob and Cox) Adult Mediterranean flour moths are short lived and do not feed. (Minn)

Life cycle

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E. kuehniella females will lay anywhere between 116 and 678 eggs in a food source such as flour to which the eggs often become attached. When the eggs hatch, larvae spin silken tubes around themselves. They spend about 40 days maturing within these tubes. Full grown larvae disperse to new locations and spin silken cocoons in which they develop into pupae. Adult moths emerge in 8-12 days.

In hot weather, the Mediterranean flour moth's entire life cycle may take no more than five to seven weeks. Though it prefers warm temperatures, E. kuehniella can complete development in temperatures ranging from 12°C to about 30°C. (J&C)

Enemies

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Parasites

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Wolbachia

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Mediterranean flour moths get infected by Wolbachia, a genus of bacteria that affects the reproduction of its host species. These maternally inherited bacteria causes cytoplasmic incompatibility in E. kuehniella, which means that sperm and eggs cannot join to form a viable embryo. Infected males produce sperm that is only compatible with eggs from infected females, resulting in a decrease in fitness for uninfected females. Different strains of Wolbachia cause different levels of cytoplasmic incompatibility.

Nemeritis canascens

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E. kuehniella is parasitized by Nemeritis canascens, a parasitic wasp of the Ichneumonidae family. The larvae of this wasp are endoparasites of the moth during the moth's larval phase. Larvae of Nemeritis feed on the blood of the host caterpillars. Nemeritis remains in its first instar until the host caterpillar is in its last instar of development. The parasitic larvae feed more quickly as the host caterpillar gets older, accounting for rapid development in late final-instar caterpillars and delayed development in first instar caterpillars. The changing rate of feeding in the parasite is attributed to the changing composition of the host blood on which it feeds.

Mating

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The maturation of both male and female reproductive systems occurs soon after emergence. Adult moths commonly mate on the day of emergence, which maximizes the reproductive success of females.[1] Female calling and male courtship behaviors peak just prior to peak mating -- these behaviors are useful in successful mating. The Mediterranean flour moth is a protogynous species, so females emerge significantly earlier than males. This mechanism may be used to reduce inbreeding, as females will emerge and mate with other males prior to their brothers emerging.

E. kuehniella is a polyandrous species.

Interactions with humans

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Pest of stored grains

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Larvae will attack stores of flour or other cereal grains as a source of food, but the most damage is done when they interfere with machinery in the mills. The web-like material that larvae spin clogs machines. Grain mills have had to shut down due to this issue.(Penn) They also cause damage by biting holes in silk screens used to sift flour. (Jacob and Cox)

Pest control

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Prevention

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The most effective pest control method for the Mediterranean flour moth is preventing it from infesting stored grains. This involves basic sanitation practices such as thoroughly cleaning out bins and surrounding areas of the floors and walls to remove old grains and particles of dust. Sealing all cracks and crevices in the building and grain bins can prevent moths from entering. Checking grain bins frequently (especially in warm months) for hot spots, mold, and insects can also reduce risk of infestation. Sanitation is generally the preferred strategy for preventing Mediterranean flour moth infestation.

Pesticides

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Insecticides are sometimes used as well as fumigants if infestation has already occurred. Both of these pest control options involve toxic chemicals and require safety precautions to use. Methyl bromide was commonly used as a pesticide in several countries, but was later banned for environmental reasons when it was classified as an ozone depleter.

Biological control

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Trichogramma parasitoids are a potential biological control for the Mediterranean flour moth, because they can kill the host in the egg stage, before it reaches the destructive larval phase. The success of Trichogramma in biological control programs is influenced by host diet and the resulting nutritional quality of the eggs. Temperature can also impact host suitability for the parasitoid.

Gamma radiation is another biological control that has been considered as an alternative to pesticide use. Low-dose irradiation has been approved by the FDA as a safe pest control measure in foods. This method is fast and not temperature dependent. Irradiation treatment can prevent adult emergence from eggs or introduce sex-linked lethal mutations that cause inherited sterility.

  1. ^ Karalius, V.; Buda, V. (November 1995). "MATING DELAY EFFECT ON MOTHS' REPRODUCTION: CORRELATION BETWEEN REPRODUCTION SUCCESS AND CALLING ACTIVITY IN FEMALES EPHESTIA KUEHNIELLA, CYDIA POMONELLA, YPONOMEUTA COGNAGELLUS (LEPIDOPTERA: PYRALIDAE, TORTICIDAE, YPONOMEUTIDAE)". Pheromones. 5: 169–190. {{cite journal}}: line feed character in |title= at position 44 (help)