Delia antiqua
Encyclopedia
Delia antiqua, commonly known as the onion fly, is a cosmopolitan
pest of crops
. The larvae
or maggot
s feed on onion
s, garlic
and other bulbous
plants.
. The male has a longitudinal stripe on the abdomen which is lacking in the female. The legs are black, the wings transparent and the compound eyes brown. The eggs
are white and elongated and are laid in groups on the shoots, leaves and bulbs of host plants and on the ground nearby. The larvae are white and cylindrical and hatch in from three to eight days. Each batch tends to keep together and collectively create large cavities in bulbs. More than fifty maggots may feed on one bulb, sometimes originating from eggs laid by several different females. The larvae moult three times, feed for about twenty days and reach a length of about one centimetre. The pupa is brown, ringed and ovoid and measures 7 millimetre (0.275590551181102 in) long. Pupation
occurs in the ground with the pupal phase from the spring generation lasting two or three weeks. Late generation pupae overwinter in the soil.
, Western Europe
, Russia
, Central Asia
, China
, Japan
and Korea
but is absent from deserts. In the far north of its range it is univoltine
but further south there may be two, three or four generations in one season.
, shallot
s, leek
s and the bulbs of flowering plants. The first generation of larvae is the most harmful because it extends over a long period owing to the female longevity and occurs when the host plants are small. Seedlings of onion and leek can be severely affected as can thinned out onions and shallots. Less damage occurs in wet and cold springs as this delays the development of the larvae. When plants are attacked, the leaves start to turn yellow and the bulbs rot quickly, especially in damp conditions. Control measures include crop rotation, the use of seed dressings, early sowing or planting, survey and removal of infested plants and autumn digging of the ground to destroy the pupae.
Cosmopolitan distribution
In biogeography, a taxon is said to have a cosmopolitan distribution if its range extends across all or most of the world in appropriate habitats. For instance, the killer whale has a cosmopolitan distribution, extending over most of the world's oceans. Other examples include humans, the lichen...
pest of crops
Crop (agriculture)
A crop is a non-animal species or variety that is grown to be harvested as food, livestock fodder, fuel or for any other economic purpose. Major world crops include maize , wheat, rice, soybeans, hay, potatoes and cotton. While the term "crop" most commonly refers to plants, it can also include...
. The larvae
Larvae
In Roman mythology, lemures were shades or spirits of the restless or malignant dead, and are probably cognate with an extended sense of larvae as disturbing or frightening...
or maggot
Maggot
In everyday speech the word maggot means the larva of a fly ; it is applied in particular to the larvae of Brachyceran flies, such as houseflies, cheese flies, and blowflies, rather than larvae of the Nematocera, such as mosquitoes and Crane flies...
s feed on onion
Onion
The onion , also known as the bulb onion, common onion and garden onion, is the most widely cultivated species of the genus Allium. The genus Allium also contains a number of other species variously referred to as onions and cultivated for food, such as the Japanese bunching onion The onion...
s, garlic
Garlic
Allium sativum, commonly known as garlic, is a species in the onion genus, Allium. Its close relatives include the onion, shallot, leek, chive, and rakkyo. Dating back over 6,000 years, garlic is native to central Asia, and has long been a staple in the Mediterranean region, as well as a frequent...
and other bulbous
Bulb
A bulb is a short stem with fleshy leaves or leaf bases. The leaves often function as food storage organs during dormancy.A bulb's leaf bases, known as scales, generally do not support leaves, but contain food reserves to enable the plant to survive adverse conditions. At the center of the bulb is...
plants.
Morphology and biology
The onion fly has an ash-grey body and resembles a houseflyHousefly
The housefly , Musca domestica, is a fly of the suborder Cyclorrhapha...
. The male has a longitudinal stripe on the abdomen which is lacking in the female. The legs are black, the wings transparent and the compound eyes brown. The eggs
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
are white and elongated and are laid in groups on the shoots, leaves and bulbs of host plants and on the ground nearby. The larvae are white and cylindrical and hatch in from three to eight days. Each batch tends to keep together and collectively create large cavities in bulbs. More than fifty maggots may feed on one bulb, sometimes originating from eggs laid by several different females. The larvae moult three times, feed for about twenty days and reach a length of about one centimetre. The pupa is brown, ringed and ovoid and measures 7 millimetre (0.275590551181102 in) long. Pupation
Pupa
A pupa is the life stage of some insects undergoing transformation. The pupal stage is found only in holometabolous insects, those that undergo a complete metamorphosis, going through four life stages; embryo, larva, pupa and imago...
occurs in the ground with the pupal phase from the spring generation lasting two or three weeks. Late generation pupae overwinter in the soil.
Distribution
The onion fly is found in North AmericaNorth America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
, Western Europe
Western Europe
Western Europe is a loose term for the collection of countries in the western most region of the European continents, though this definition is context-dependent and carries cultural and political connotations. One definition describes Western Europe as a geographic entity—the region lying in the...
, Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
, Central Asia
Central Asia
Central Asia is a core region of the Asian continent from the Caspian Sea in the west, China in the east, Afghanistan in the south, and Russia in the north...
, China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
, Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
and Korea
Korea
Korea ) is an East Asian geographic region that is currently divided into two separate sovereign states — North Korea and South Korea. Located on the Korean Peninsula, Korea is bordered by the People's Republic of China to the northwest, Russia to the northeast, and is separated from Japan to the...
but is absent from deserts. In the far north of its range it is univoltine
Voltinism
Voltinism is a term used in biology to indicate the number of broods or generations of an organism in a year. The term is particularly in use in sericulture, where silkworm varieties vary in their voltinism....
but further south there may be two, three or four generations in one season.
Economic significance
The larvae damage bulb onions, garlic, chivesChives
Chives are the smallest species of the edible onions. A perennial plant, they are native to Europe, Asia and North America.. Allium schoenoprasum is the only species of Allium native to both the New and the Old World....
, shallot
Shallot
The shallot is the botanical variety of Allium cepa to which the multiplier onion also belongs. It was formerly classified as the species A. ascalonicum, a name now considered a synonym of the correct name...
s, leek
Leek
The leek, Allium ampeloprasum var. porrum , also sometimes known as Allium porrum, is a vegetable which belongs, along with the onion and garlic, to family Amaryllidaceae, subfamily Allioideae...
s and the bulbs of flowering plants. The first generation of larvae is the most harmful because it extends over a long period owing to the female longevity and occurs when the host plants are small. Seedlings of onion and leek can be severely affected as can thinned out onions and shallots. Less damage occurs in wet and cold springs as this delays the development of the larvae. When plants are attacked, the leaves start to turn yellow and the bulbs rot quickly, especially in damp conditions. Control measures include crop rotation, the use of seed dressings, early sowing or planting, survey and removal of infested plants and autumn digging of the ground to destroy the pupae.