Spodoptera exempta

from Wikipedia, the free encyclopedia
Spodoptera exempta
Spodoptera exempta caterpillar

Spodoptera exempta caterpillar

Systematics
Superfamily : Noctuoidea
Family : Owl butterfly (Noctuidae)
Subfamily : Xyleninae
Tribe : Prodeniini
Genre : Spodoptera
Type : Spodoptera exempta
Scientific name
Spodoptera exempta
( Walker , 1856)

Spodoptera exempta is a species of butterfly from the owl butterfly family(Noctuidae). Your caterpillar is called a command worm ( Afrikaans ), in English as an African Armyworm , Black Caterpillar or Swarming Caterpillar . The mass reproduction of the butterfly species, which occasionally occurs in Africa, causes great damage to pastures and to cultivated plants from the grass family. The excrement of the caterpillars can cause allergic reactionsin humansand contaminate the drinking water.

features

The moth has a wingspan of 20–37 mm, with the females being slightly larger on average. The basic color of the upper side of the forewing is a dark gray-brown. The hind wings, on the other hand, are whitish with dark veins. The forewings usually have ring and kidney defects on the upper side. Inner cross line, outer cross line and wavy line are whitish and bordered more or less black. Males and females do not differ in the coloring and drawing of the wings. However, the frenulum is multiple in the males and single in the females.

The eggs measure 0.5 mm in diameter and are initially whitish, but become blackish shortly before the egg caterpillars hatch.

The caterpillars are colored green by about the third moult. In these stages they are 1 to 5 millimeters long. After that, the color changes depending on the density of individuals. If there is a high density of individuals, the caterpillars become velvety black with light side lines and a greenish-yellow underside. If the density of individuals is low, the basic color varies from green to brown. The caterpillars are 25 to 35 mm long until pupation.

The pupa is dark brown or black and up to 17 mm long.

Geographical distribution and habitat

Spodoptera exempta occurs in almost all of Africa and parts of Asia, in eastern Australia and parts of New Zealand as well as in Hawaii, at times in large numbers. The countries of South , Central , East and West Africa are affected by mass reproductions . The moth is also found in India , Indonesia , Malaysia and the Philippines , but is less common there and its harmful effects are low. This owl butterfly species is most common in the countries around Mozambique and Zimbabwe . The moth spreads seasonally from the countries of East Africa, south to Namibia and South Africa and north to Ethiopia , Eritrea , Somalia and the south-western part of the Arabian Peninsula . The species is less common in the West African countries south of the Sahara .

Way of life

The species is multivoltin under favorable circumstances, i.e. H. new generations are constantly being formed. There is no diapause during the pupal phase.

The females lay 100 to 400 eggs in small groups in one night, covered with black scales from the female's abdomen and often attached to the underside of the leaves of the food plants. In total, a female can lay up to 1000 eggs. The moths can live up to 14 days and are very happy to migrate. They are nocturnal and are attracted to artificial light sources.

The caterpillars hatch after two to five days. They develop into a pupa through six caterpillar stages within two to three weeks . The preferred diet of the caterpillars is various grasses , including rice , corn , wheat , sorghum and other crops . The pastures for livestock and the grain fields are particularly affected by mass infestation . The preference for grass has occasionally led to the German-language name grass owl , which is also used for many other grass-eating owl butterflies and therefore cannot be clearly applied to this species. The young caterpillars initially spread and are unsociable. They are nocturnal and relatively sluggish. If a young caterpillar encounters a conspecific (or representatives of closely related species) several times, it becomes very active, also eats during the day and likes to sunbathe. The metabolic rate increases sharply. Due to the high population density itself, but also due to the higher metabolic rate of the caterpillars triggered by the high population density, the caterpillars quickly erode and begin to migrate. In long rows next to each other, the crawler move from field to field, leading to the trivial name Armyworm (army worm), and command worm has led.

Before pupating, the caterpillar digs 2 to 3 centimeters deep into the ground. The moths appear after the pupa has rested for seven to ten days . The life cycle of a generation therefore lasts around a month. During the rainy season between December and April, when the sexually mature animals appear in East Africa, for example, several generations can develop.

Mass reproduction

A massive occurrence of the command worm takes place at irregular intervals. Often only a relatively small area is affected, sometimes the area in which the caterpillars cause damage to the plants extends over thousands of square kilometers. The spread and multiplication depends on the weather. Hot years with a delayed onset of the rainy season favor this. The mass infestation sets in with the beginning of the rainy season. Up to 1000 caterpillars can then be counted on one square meter in the fields.

hikes

The sudden appearance of caterpillars in areas where the species has not previously been observed has led to the assumption that the moths can migrate long distances of tens, perhaps hundreds of kilometers. Studies have shown that the butterflies can stay in the air for several hours without stopping. Wind and weather conditions play an important role in the spread. The moths can travel up to 100 km per day in the direction of the wind.

Natural enemies

Spodoptera exempta has many enemies at all stages. The caterpillars are attacked by 28 different species of caterpillar flies from the Tachinidae family. In the waist wasp group , 25 species were found that parasitize eggs, caterpillars or pupae. Ants and various types of beetles eat the eggs and especially the early larval stages. A mass occurrence also attracts birds. The caterpillars are part of the food spectrum for marabous and storks , including the African Abdim stork . Up to 90% of the caterpillars are occasionally killed by a nuclear polyhedron virus (NPV). The pupae are infected by a cytoplasmic virus. A fungus ( Nomuraea rileyi ) can also attack the caterpillars under certain conditions (high humidity and high temperatures). When infested, the caterpillars climb up blades of grass and die there, completely overgrown by mycelium.

Harmful effect

When examining an area of ​​65 square kilometers of pasture land with an average density of 28 individuals of the command worm per square meter, it was found that the caterpillars can destroy 50 tons (dry weight) of plant matter per day. This corresponds to the daily feed requirements of a herd of 8,000 cattle . Grazing animal losses can also occur through a phenomenon called armyworm-related cattle poisoning (ARCP). Due to the strong infestation by caterpillars of Spodoptera exempta, some grasses excrete more hydrogen cyanide. The previously harmless plants become poisonous.

Mass infestation

In East Africa there is an annual mass increase between December and April. However, they vary in intensity and the size of the infested area. For example, while there was only isolated damage to the fields in Tanganyika in 1961 , the northern neighboring country Kenya was so badly affected by the infestation that the insecticide reserves were soon exhausted. The moths migrate from East Africa to the south and north, where they can still cause great damage in the months of May to August. The yield loss for maize in an average infestation year is estimated at around 30% in East Africa.

Combat

In order to be able to fight the command worms in good time, notification and advance warning systems have been set up in most of the affected countries, ranging from the individual villages to central offices. One of the most important signs of an impending infestation is the occurrence of an increased number of individuals in the butterfly. This is often checked by setting up light or pheromone traps . Insecticides are mainly applied by airplanes because of the large areas. Smaller areas can be sprayed with hand or motorized spray pumps. The caterpillars can also be prevented from advancing further by drawing long trenches. They then move on along the trenches where they fall into prepared deep holes and can be collected.

The Food and Agriculture Organization of the United Nations (FAO) recommends methods of biological pest control instead of the use of pesticides . The oil obtained from the seeds of the neem tree ( Azadirachta indica ) native to Africa contains the insecticidal azadirachtin , which inhibits the larval development of insects. It seems to be a natural protection against plant pests. With the Spodoptera exempta nucleopolyhedrovirus (SpexNPV) from the Baculoviridae family , which occurs in the range of the command worm, the massive reproduction of the butterfly can also be combated biologically. After it has been applied to the infected fields, the virus multiplies in large numbers within the caterpillars and can be transmitted to other individuals.

Taxonomy

The species was first described by Walker in 1856 as Agrotis exempta . Later it was known for a long time under the scientific name Laphygma exempta .

Web links

Commons : Spodoptera exempta  - collection of images, videos and audio files

swell

literature

  • John L. Capinera (Ed.): Encyclopedia of Entomology, Volume 1. 2nd ed., Springer 2008 ISBN 978-1-4020-6242-1
  • CC Hattingh: Die biologie en ekologie van die Kommandowurm (Laphygma exempta) en die bestryding van die plaag in Suid-Afrika. Science bulletin (South Africa. Dept. of Agriculture and Forestry), 217, Entomology series, 2, 1942
  • MJ Haggis: Distribution of the African armyworm, Spodoptera exempta (Walker) (Lepidoptera: Noctuidae), and the frequency of larval outbreaks in Africa and Arabia. Bulletin of Entomological Research 76, pp. 151-170, 1986

Individual evidence

  1. ↑ a b Capinera (2008: p. 53ff.)
  2. ^ A b Gordon Swaine: Fighting the army worm. New Scientist, 326, pp. 357-358, February 14, 1963
  3. ^ South West Africa annual - Südwestafrika Jahrbuch, p. 73, 1959
  4. ↑ CF Dewhurst: The African armyworm ( Spodoptera exempta ) - the East African story outlined from 1962. Antenna 9, pp. 12-18, 1985
  5. ↑ W. Mushobozi, D. Grzywacz, R. Musebe, M. Kimani and K. Wilson: New approaches to improve the livelihoods of farmers and pastoralists through monitoring and control of African armyworm, Spodoptera exempta. Ministry of Agriculture and Food Security, Pest Control Services, Tanzania 2006, p. 4 (PDF, English; 2.1 MB)
  6. ↑ JR Riley, DR Reynolds, MJ Farmery: Observations of the flight behavior of the armyworm moth Spodoptera exempta, at an emergence site using radar and infra-red optical techniques. Ecological Entomology, 8, pp. 395-418, 1983
  7. ↑ AG Gatehouse and DS Hackett: A technique for studying flight behavior of tethered Spodoptera exempta moths. Physiological Entomology, 5, pp. 215-222, 1980
  8. ↑ DJW Rose, WW Page, CF Dewhurst, JR Riley, DR Reynolds, DE Pedgley, and MR Tucker: Downwind migration of the African armyworm moth, Spodoptera exempta, studied by mark and capture and by radar. Ecological Entomology, 10, pp. 299-313, 1985
  9. ↑ PO Odiyo: Forecasting infestations of a migrant pest: the African armyworm, African armyworm (Walk.). In: DL Gunn, RC Rainey (Orgs.): Strategy and tactics of control of migrant pests. Phil. Trans. R. Soc. (B), 287, pp. 245-488, 1979, pp. 403-413
  10. ↑ Wilfred L. Mushobozi, David Grzywacz, Richard Musebe, Martin Kiman and Ken Wilson: New approaches to improve the livelihoods of poor farmers and pastoralists in Tanzania through monitoring and control of African armyworm, Spodoptera exampta. Aspects of Applied Biology 75: 73-45, 2005 PDF
  11. ^ ES Brown, E. Betts, RC Rainey: Seasonal changes in distribution of the African armyworm, Spodoptera exempta (Wlk.) (Lep. Noctuidae) with special reference to Eastern Africa. Bull. Ent. Res., 58, pp. 671-684, 1969
  12. ↑ W. Mushobozi, D. Grzywacz, K. Wilson, Jenny Cory, Flavio Moscardi, Roger Day: Novel technologies for control of African armyworm on smallholder cereals in East Africa ( Memento of the original September 8, 2008 at the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 397 kB) @1@ 2Template: Webachiv / IABot / www.nri.org . DFID Crop Protection Program, pp. 93-95, 2001-2004
  13. ↑ 2003 Armyworm Outbreak in South Africa  ( page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. Agricultural Research Council, Information Core for Southern African Migrant Pests, 2003@1@ 2Template: Dead Link / www.arc.agric.za  
  14. ↑ FAO: Biological control of army worm (Spodoptera exempta) in Tanzania.
  15. ↑ W. Mushobozi, D. Grzywacz: NPV a new biological control for the armyworm in Tanzania. Ministry of Agriculture and Food Security, Pest Control Services, Tanzania 2006 (PDF, English; 97 kB)