Wheat weevil | |
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Illustration by Des Helmore | |
Scientific classification ![]() | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Arthropoda |
Class: | Insecta |
Order: | Coleoptera |
Family: | Curculionidae |
Subfamily: | Dryophthorinae |
Tribe: | Litosomini |
Genus: | Sitophilus |
Species: | S. granarius |
Binomial name | |
Sitophilus granarius | |
Synonyms | |
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The wheat weevil (Sitophilus granarius), also known as the grain weevil or granary weevil, is an insect that feeds on cereal grains, and is a common pest in many places. It can cause significant damage to harvested stored grains and may drastically decrease crop yields. The females lay many eggs and the larvae eat the inside of the grain kernels.
Adult wheat weevils are about 3–5 mm (0.12–0.20 in) long with elongated snouts and chewing mouth parts. [2] Depending on the grain kernels, the size of the weevil varies. In small grains, such as millet or grain sorghum, they are small in size, but are larger in maize (corn). [3] The adults are a reddish-brown colour and lack distinguishing marks. Adult wheat weevils are not capable of flight. Larvae are legless, humpbacked, and are white with a tan head. Weevils in the pupal stage have snouts like the adults.
Female wheat weevils lay between 36 and 254 eggs and usually one egg is deposited in each grain kernel. All larval stages and the pupal stage occur within the grain. The larvae feed inside the grain until pupation, after which they bore a hole out of the grain and emerge. They are rarely seen outside of the grain kernel. The life cycle takes about five weeks in the summer, but may take up to 20 weeks in cooler temperatures. [4] Adults can live up to eight months after emerging.
Adult wheat weevils when threatened or disturbed will pull their legs close to their bodies and feign death. Female weevils can tell if a grain kernel has had an egg laid in it by another weevil. [5] They avoid laying another egg in this grain. Females chew a hole, deposit an egg, and seal the hole with a gelatinous secretion. This may be how other females know the grain has an egg in it already. This ensures the young will survive and produce another generation. One pair of weevils may produce up to 6,000 offspring per year.
The species is not found "in the wild", but only in human food-storage situations. [6]
Wheat weevils are pests of stores of grains of the cereal crops wheat, oats, rye, barley, rice and maize. Unfortunately the impact of wheat weevils worldwide is unknown because information is not well shared. It is believed to be especially bad in places where the grain harvests are not accurately measured. The weevils are hard to detect and usually all of the grain in an infested storage facility must be destroyed. Many methods have been attempted to get rid of the wheat weevil, such as pesticides, different methods of masking the odor of the grain with unpleasant scents, and some have even gone as far as introducing predator organisms. [7]
Sanitation and inspection are key to preventing infestation. Grains should be stored in preferably metallic (cardboard, even fortified, is easily drilled through by the weevil) containers with tight lids in a refrigerator or a freezer, and should be purchased in small quantities. If any suspicion has arisen, carefully examine the grains for adult insects or holes in the grain kernels. Another method is to immerse them in water. If they float to the surface, it is a good indication of infestation. Even if identified early, disposal may be the only effective solution.[ citation needed ]
The Curculionidae are a family of weevils, commonly called snout beetles or true weevils. They are one of the largest animal families with 6,800 genera and 83,000 species described worldwide. They are the sister group to the family Brentidae.
Weevils are beetles belonging to the superfamily Curculionoidea, known for their elongated snouts. They are usually small – less than 6 mm in length – and herbivorous. Approximately 97,000 species of weevils are known. They belong to several families, with most of them in the family Curculionidae. It also includes bark beetles, which while morphologically dissimilar to other weevils in lacking the distinctive snout, is a subfamily of Curculionidae. Some other beetles, although not closely related, bear the name "weevil", such as the leaf beetle subfamily Bruchinae, known as "bean weevils", or the biscuit weevil, which belongs to the family Ptinidae.
The drugstore beetle, also known as the bread beetle, biscuit beetle, and misnamed as the biscuit weevil, is a tiny, brown beetle. It can be found infesting a wide variety of dried plant products, where it is among the most common non-weevils to be found. It is the only living member of the genus Stegobium. It belongs to the family Ptinidae, which also includes the deathwatch beetle and furniture beetle. A notable characteristic of this species is the symbiotic relationship the beetles have with the yeast they carry, which are transmitted from female to larvae through the oviduct.
Sitophilus is a genus of weevils in the tribe Litosomini. Some species are familiar as pests of stored grain, nut, or seed. Notable pest species include the rice weevil, wheat weevil, and maize weevil.
The Indianmeal moth, also spelled Indian meal moth and Indian-meal moth, is a pyraloid moth of the family Pyralidae. Alternative common names are hanger-downers, weevil moth, pantry moth, flour moth or grain moth. The almond moth and the raisin moth are commonly confused with the Indian-meal moth due to similar food sources and appearance. The species was named for feeding on Indian meal or cornmeal, and does not occur natively in India. It is also not to be confused with the Mediterranean flour moth, another common pest of stored grains.
The African armyworm, also called okalombo, kommandowurm, or nutgrass armyworm, is a species of moth of the family Noctuidae. The larvae often exhibit marching behavior when traveling to feeding sites, leading to the common name "armyworm". The caterpillars exhibit density-dependent polyphenism where larvae raised in isolation are green, while those raised in groups are black. These phases are termed solitaria and gregaria, respectively. Gregaria caterpillars are considered very deleterious pests, capable of destroying entire crops in a matter of weeks. The larvae feed on all types of grasses, early stages of cereal crops, sugarcane, and occasionally on coconut. The solitaria caterpillars are less active and undergo much slower development. The species is commonly found in Africa, but can also be seen in Yemen, some Pacific islands, and parts of Australia. African armyworm outbreaks tend to be devastating for farmland and pasture in these areas, with the highest-density outbreaks occurring during the rainy season after periods of prolonged drought. During the long dry seasons ("off-season"), the population densities are very low and no outbreaks are seen.
The khapra beetle, also called cabinet beetle, which originated in South Asia, is one of the world's most destructive pests of grain products and seeds. It is considered one of the 100 worst invasive species in the world. Infestations are difficult to control because of the insect's ability to survive without food for long periods, its preference for dry conditions and low-moisture food, and its resistance to many insecticides. There is a federal quarantine restricting the importation of rice into the U.S. from countries with known infestations of the beetle. Khapra beetle infestation can spoil otherwise valuable trade goods and threaten significant economic losses if introduced to a new area. Handling or consuming contaminated grain and seed products can lead to health issues such as skin irritation and gastrointestinal distress.
Oryzaephilus surinamensis, the sawtoothed grain beetle, is a beetle in the superfamily Cucujoidea. It is a common, worldwide pest of grain and grain products as well as chocolate, drugs, and tobacco. The species' binomial name, meaning "rice-lover from Suriname," was coined by Carl Linnaeus, who received specimens of the beetle from Surinam. It is also known as the malt beetle and may be referenced in the poem This Is The House That Jack Built in the line "....the rat that ate the malt that lay in the house that Jack built" the malt referenced may not be actual malted grain but a sawtoothed grain beetle.
Lasioderma serricorne, more commonly referred to as the cigarette beetle, cigar beetle, or tobacco beetle, is a small beetle that shares a remarkable resemblance with the drugstore beetle and the common furniture beetle. The cigarette beetle, along with the drugstore and furniture beetles, all belong to the beetle family Ptinidae. The cigarette beetle can be distinguished from A. punctatum by its flatter thorax, whereas the A. punctatum boasts a humped thorax. The cigarette beetle can be further differentiated from S. paniceum with its uniformly serrated antennae with unmodified apex, unlike the three-segmented apical "club" of S. paniceum. Additionally, L. serricorne has more no grooves in its elytra, or hardened wing covers, compared to A. punctatum and S. paniceum’s deep grooving.
Home-stored product entomology is the study of insects that infest foodstuffs stored in the home. It deals with the prevention, detection and eradication of pests.
The rice weevil is a stored product pest which attacks seeds of several crops, including wheat, rice, and maize.
Tenebroides mauritanicus, commonly known as the cadelle, is a species of beetle in the family Trogossitidae. It is a common cosmopolitan pest in storehouses and granaries.
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The maize weevil, known in the United States as the greater rice weevil, is a species of beetle in the family Curculionidae. It can be found in numerous tropical areas around the world, and in the United States, and is a major pest of maize. This species attacks both standing crops and stored cereal products, including wheat, rice, sorghum, oats, barley, rye, buckwheat, peas, and cottonseed. The maize weevil also infests other types of stored, processed cereal products such as pasta, cassava, and various coarse, milled grains. It has even been known to attack fruit while in storage, such as apples.
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Sphenophorus parvulus, commonly known as the bluegrass billbug, is a species of beetle in the true weevil family Curculionidae. It is found in North America, especially in the eastern United States. It is a pest of Kentucky bluegrass, corn and grain crops.
Curculio sayi, the small or lesser chestnut weevil, is a species of true weevil in the family of beetles known as Curculionidae.
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Lariophagus distinguendus is a idiobiont ectoparasitoid hymenopteran in the family Pteromalidae, superfamily Chalcidoidea. It parasitizes small beetle larvae concealed in seeds, as well as prepupae and pupae in their cocoons. It is used for the biological control of several beetle pests of stored products, particularly in central Europe, where it is produced commercially and distributed by at least 11 companies.