Pests
Autographa gamma L. - Gamma Moth
Systematic position.
Class Insecta, order Lepidoptera, family Noctuidae, genus Autographa.Synonym.
Phytometra gamma L.Biological group.
These are polyphagous pests.Morphology and biology.
Moth size and coloration varies insignificantly. Sexual dimorphism is not pronounced. Wing span is 40-48 mm. Forewing varies from gray to black-brown or violet-brown, having silver shining spot looking like the Greek letter gamma. Round and reniform spots have narrow shiny border. Transversal stripes are in twos, interval between the stripes is darkened. Hind-wing is grayish-yellow, with broad brownish border along margin of wings. Fecundity varies from 500 to 1500 eggs. Eggs are laid as one or in groups of two, rarely in groups of 3-6 on underside of leaves of both weeds and cultivated plants. Development of eggs lasts 3-7 days. Eggs have an oval shape (0.5-0.6 mm in diameter and 0.3-0.4 mm in height) and costate surface; their color is watery-white with a greenish-yellow hue. Larvae develop over 16-25 days, with 5 instars usually (very rarely 6 instars), reaching 24-40 mm in length in the last instar. Larvae greenish-yellow or green, with indistinct pattern; two white twisting lines pass along dark nodal side, a light yellow stripe crosses along the lateral body side along spiracle line. Head is light, with dark-brown fine spots and with black coloring on each lateral side. Only 3 pairs of abdominal legs are present (the legs are absent on the 3rd and 4th abdominal segments). Larvae pupate in various places: in a white thin web cocoon at the top part of plants or under the rolled edge of a leaf in summer; on surface layer of soil under residues in autumn. Pupal stage lasts 6-13 days. Pupae are dark-brown. Body length reaches 17 to 25 mm. There is a strongly extended cremaster with a big doubled hook at the end of last segment and with four fine hooks around it. Over-wintering usually occurs during the stages of larva and pupa, but sometimes during the moth stage. Development of one generation lasts 25-45 days.Distribution.
Widely distributed all over the world: in the Caucasus, Transcaucasia, Central Asia, Anterior Asia, Kazakhstan, Afghanistan, Hindustan, China, Japan, Northern Africa, Ukraine, Belarus, Baltics, the Western Europe, Northern America. In European Russia the Gamma Moth reaches Arkhangelsk, Syktyvkar, and Perm in the north; it is also distributed in Cis-Ural, Western Siberia, Transbaikalia, and the Far East. It is found in the south of Sakhalin and on Kunashir island.Ecology.
This is a polyvoltine species. In northern regions of European Russia, in the Baltics and Western Siberia, it develops in 1 generation; in the central regions of European Russia and in the Far East in 2 generations; in the Northern Caucasus and Ukraine in 2-3 generations. Up to 4 generations can develop in Central Asia, Kazakhstan, and Transcaucasia (5 generations in places). The Gamma Moth is known as a good migrant, especially during the years of mass reproduction. This is a hygrophilic and thermophilic species. The sum of Degree Days for the development of 1 generation is 515°C at a threshold of +10°C. Optimum temperature for larvae is about 23-30°C, about 25°C for pupae, and about 20-25°C for moths. Optimum relative air humidity is 80-95%. Moth flight in southern and central zones is observed at the end of May and in the first half of June and proceeds throughout all summer months, coming to an end in September. In northern zones, flight is observed from the end of June until September. In Abkhazia the moths fly from March until January. The females require additional feeding on nectar from blossoming plants for oviposition. As opposed to other noctuids the Gamma Moth imagoes are active both in the afternoon and at night. Gamma Moth development depends on temperature and sum of precipitation, on the presence or absence of snow cover during autumn-winter period, and also upon conditions of larva feeding. Entomophages (predators and parasites) and entomopathogens influence pest numbers, as well as migration of moths seeking blossoming plants for additional feeding. The Gamma Moth larvae are polyphages, eating plants of 311 species of various families. Larvae of all instars feed mainly on leaves, sometimes on young shoots, buds, and flowers. Larvae cause the most harm during 4-5th instars, roughly gnawing out and eating around leaf plate. Naturally this noctuid prefers to develop on plants of families Asteraceae, Brassicaceae and Lamiaceae. Starting to feed on weeds, the larvae move later to cultivated plants. Outbreaks of mass reproduction that last 1-2 years and following long-term depressions are characteristic of this species. Larvae transfer the tobacco mosaic virus.Economic significance.
The pest causes major damage to annual and perennial leguminous cultures, sugar beet, potato, vegetables, industrial (flax, hemp), and various aromatic cultures. Cases of damage caused to corn and sunflower are known. During migrations with outbreaks of mass reproduction the larvae can damage trees and bushes (willow, alder, hazel-nut, black currant). The economic threshold of harmfulness for this species as a whole on occupied field cultures is 5-8 larvae/1 sq.m. Control measures include: weeding, inter-row cultivations, removal of crop residues from fields, deep autumn plowing, optimal dates of early sowing, insecticide treatments of seeds and plantlets, releases of such entomophages as Trichogramma spp., and also the use of biological preparations. Monitoring is possible with the use of sex pheromone traps.Reference citations:
Kononenko V.S. 2003. Noctuidae. In: Ler P.A., ed. Keys to the insects of the Russian Far East. V. 5(4). Trichoptera and Lepidoptera. Vladivostok: Dal.nauka. 688 p. (In Russian)Makarova L.A, Doronina G.M. 1994. The synoptic approach to forecasting long-range migration of insect pests. St. Petersburg: Gidrometeoizdat. 199 p. (In Russian)
Pospelov S.M. 1975. Zoning of territory of Soviet Union by noctuid complexes harming to agricultural crops. In: Berim N.G., ed. Zapiski LSKHI. V. 270. Leningrad-Pushkin: LSKHI. 75-81 p. (In Russian)
Pospelov S.M. 1989. Noctuids - pests of agricultural crops. Moscow: Agropromizdat. 112 p. (In Russian)
Shchegolev V.N., Znamenskii A.V., Bei-Bienko G.Ya. 1934. Insect pests on field crops. Leningrad-Moscow: Sel.khozgiz. 364 p. (In Russian)
Sukhareva I.L. 1999. Noctuidae. In: Kuznetsov V.I., ed. Insects and mites - agricultural pests. V. 3, Part 2. Lepidoptera. St. Petersburg: Nauka. 332-378 p. (In Russian)
Vasil'ev V.P., ed. 1974. The pests of agricultural crops and forest plantations. V. 2. Kiev: Urozhai. 606 p. (In Russian)