Alfalfa weevil | |
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Species: | H. postica |
Binomial name | |
Hypera postica (Gyllenhal, 1813) | |
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Rhynchaenus postica Gyllenhal, 1813 |
Hypera postica, commonly known as the alfalfa weevil, is a species of beetle in the superfamily Curculionoidea ; it can be found in alfalfa fields throughout Europe. [1] Considered a destructive threat to alfalfa production in North America, several accidental introductions have been successfully countered though the use of a variety of biological control species.
The alfalfa weevil grows to a length of about 4 to 5.5 mm (0.16 to 0.22 in). The rostrum or beak is short and broad. The frons is half as wide as the rostrum while the pronotum is broadest in the centre. The general colour of the insect is brown, with a dark mid-dorsal stripe. The larva has a distinctive black head and no legs; it is yellowish-green, with a white dorsal stripe and faint white lateral stripes. It is about 1 cm (0.4 in) long just before pupation. It pupates in a white, pea-sized cocoon made of loosely-woven silk. [2] It resembles the clover leaf weevil ( Hypera punctata ), but that species is nearly twice as large, the larvae have tan heads and they seldom cause much damage to alfalfa crops. [2] [3]
In Illinois, some eggs are laid in the late fall or the winter, when weather conditions permit. Adults also overwinter and become increasingly active in March and April. Eggs are laid in batches of up to 25 inside alfalfa stems. The larvae feed for three or four weeks, moulting three times, before pupating in the cocoons they make. They emerge as adults in about one or two weeks. After feeding for a week or two, they may experience aestivation during the remainder of the summer, in which they demonstrate a dampening of their metabolic, respiratory and nervous system activities. [4] [5] [6] [7] In fall, the adults hide in the crowns of alfalfa plants or move onto coarse vegetation in ditches or by fences or in nearby woodland. [2]
Both the larvae and the adults are diurnal and feed on the foliage of alfalfa, the larvae doing the most damage. The adults eat the edges of the leaves, giving them a feathery appearance. At first, the larvae feed on terminal leaves leaving puncture marks, but they later move down the plant to feed on lower leaves. The leaves attacked are skeletonised as the larvae feed between the veins, and plant yields can be reduced by up to 15%. Sometimes the larvae are killed by the pathogenic fungus Zoophthora phytonomi , especially in warm and humid weather. They may also be parasitized by ichneumon wasps, Bathylplectes anurus and B. curculionis . The female of these wasps is only about 0.125 in (0.32 cm) long, and lays an egg inside an early stage of the larva of the weevil. The developing wasp larva is a parasitoid, living inside the weevil larva and devouring it, eventually pupating soon after its host. The wasp's brownish cocoon has a broad white band in the case of B. curculionis, and a narrower, raised one in the case of B. anurus. When it is disturbed, the cocoon of the latter species can "jump" several centimetres to avoid predation. [2] [8] Both these species of wasp have been investigated for their potential for biological control of the weevil, and B. anurus is generally considered superior to B. curculionis because of its higher reproductive rate. [8]
Aestivation is a state of animal dormancy, similar to hibernation, although taking place in the summer rather than the winter. Aestivation is characterized by inactivity and a lowered metabolic rate, that is entered in response to high temperatures and arid conditions. It takes place during times of heat and dryness, which are often the summer months.
Megachile rotundata, the alfalfa leafcutting bee, is a European bee that has been introduced to various regions around the world. As a solitary bee species, it does not build colonies or store honey, but is a very efficient pollinator of alfalfa, carrots, other vegetables, and some fruits. Because of this, farmers often use M. rotundata as a pollination aid by distributing M. rotundata prepupae around their crops. Each female constructs and provisions her own nest, which is built in old trees or log tunnels. Being a leafcutter bee, these nests are lined with cut leaves. These bees feed on pollen and nectar and display sexual dimorphism. This species has been known to bite and sting, but it poses no overall danger unless it is threatened or harmed, and its sting has been described as half as painful as a honey bee's.
Manduca sexta is a moth of the family Sphingidae present through much of the Americas. The species was first described by Carl Linnaeus in his 1763 Centuria Insectorum.
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The wattle bagworm is a species of moth in the family Psychidae. In southern Africa it is a pest of the black wattle which is grown largely as a source of vegetable tannin. Kotochalia junodi is indigenous to Southern Africa, where it originally fed on indigenous relatives of the wattle.
Anthonomus eugenii is known as the pepper weevil. This beetle feeds and lays eggs on plants in the genus Capsicum and a few species in the genus Solanum. A. eugenii is native to Mexico, however, it is an important pest of Capsicum in Florida, Puerto Rico, and Central America.
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Cylindrocopturus adspersus, the sunflower stem weevil, is a species of true weevil in the beetle family Curculionidae. It is found in North America, where the larvae tunnel in the stems of wild and cultivated sunflower plants.
Nealiolus curculionis is a species of parasitic wasp in the family Braconidae. It is a parasitoid of the sunflower stem weevil Cylindrocopturus adspersus, and a number of other species of stem-boring weevils.
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