Autographa gamma (Linnaeus)
(Sometimes placed in the genus Plusia).
Taxonomic placing:Insecta, Holometabola, Lepidoptera, Noctuidae.
Common name: Silver Y moth, gamma owlet.
Geographical distribution: Autographa gamma occurs in Europe (up to Greenland), the Middle East, North Africa, Asia to Japan and in eastern America.
Host plants: A highly polyphagous pest that feeds on more than 200 wild and cultivated plants.
Morphology: The body of the adult is light brown, about 15 mm in length. Forewings red-brown with white crosslines and a silvery Y-shaped mark in the center. Hindwingd pale-brown, becoming darker at the posterior margins. Larva green with whitish dorsal lines and lateral pale stripes. The body is 35-40 mm long, widens towards the posterior end and bears 3 pairs of prolegs.
Life cycle: In the Middle East the pest raises 4-5 annual generations, mostly between December to February, because local summer conditions are unfavorable. In spring the moth migrates northwards, such migrations leading to pest populations becoming distributed from North Africa to northern countries like Greenland and Finland. The moths can fly over long distances, sometimes in huge swarms consisting of millions of individuals. Parts of the population remain in different localities along the path of migration. Females feeds on nectar, lay up to 1000 eggs each and live for about two weeks. The eggs are placed on the underside of leaves, on which the emerging larvae feed; at maturity they pupate within a silvery cocoon attached to the leaf surface. A generational develops in 1.5 to 4 months.
Economic importance: Damage is caused by the larvae, which feed at night on leaves and may skeletonize them, leaving plants with a brownish appearance. At times the foliage is completely consumed, leaving only part of the midrib. Major crops affected include vegetable and flower crops, as well as fruits trees in the field and in greenhouses. In outbreak years large pest numbers invade fields and cause much damage; such outbreaks however are infrequent in the Eastern Mediterranean region and persist only for one generation.
Management
Monitoring: Light traps, or traps baited with the sex pheromone are placed at crop height on the borders of fields, and raised as the crop grows. Susceptible crops should be inspected for the presence of eggs, larvae or pupae.
Horticultural methods: The removal of weeds, on which the pest may develop, reduces its populations.
Biological control: Autographa gamma is attacked by many parasitoids in different parts of the world, but their overall effect is not clear. Trichogramma evanescens Westwood (Tricogrammatidae), attacks the eggs of A. gamma. It occurs naturally in the Middle East and is produced for distribution. Another parasitoid found in Egypt is Exorista larvarum (Linnaeus) (Tachinidae); others include Apanteles ruficrus (Haliday) and Bracon hebetor Say, both Braconidae. Baculoviruses that kill A. gamma larvae are available; they have no effect on the parasitoids.
References
Brambila, J., Jackson, L. and Meagher, R. 2010. Plastic bucket trap protocol. http://caps.ceris.purdue.edu/webfm_send/398.
Dunkelblum E. and Gothilf, S. 1983. Sex pheromone components of the gamma moth, Autographa gamma (L.) (Lepidoptera: Noctuidae). Zeitschrift für Naturforschung 38c: 1011-1014.
EPPO, 2014. PQR database. Paris, France: European and Mediterranean Plant Protection Organization. http://www.eppo.int/DATABASES/pqr/pqr.htm.
Harakly, F.A. 1975. Biological studies on the loopers Autographa gamma (L.) and Cornutiplusia circumflexa (L.) (Lep., Noctuidae) infesting truck crops in Egypt. Zeitschrift für Angewandte Entomologie 78: 285-290.
Kaygin, A.T., Yildiz, Y. and Avci, M. 2009. Lepidoptera fauna in Bartin province, in western black sea region of Turkey. African Journal of Agricultural Research 4: 815 - 822.
Maceljski, M. and Balarin, I. 1976. Parasites of the silver Y moth (Autographa gamma L.) in the world and in Yugoslavia. Acta Entomologica Jugoslavica 11: 109-124.
Mazor, M. and E. Dunkelblum. 2005. Circadian rhythms of sexual behavior and pheromone titers of two closely related moth species Autographa gamma and Cornutiplusia circumflexa. Journal of Chemical Ecology 31: 2153–2168.
Pedgley, D. and S. Yathom. 1993. Windborne moth migration over the Middle East. Ecological Entomology 18: 67-72.
Stoianova, E.E. 2007. The effect of the nuclear polyhedrosis viruses (NPVs) of some Noctuidae species on the longevity of Bracon hebetor Say (Hymenoptera: Braconidae). Bulgarian Journal of Agricultural Science 13: 197-203.
Venette, R.C., Davis, E.E., Heisler, H. and Larson, M. 2003. Mini risk assessment silver Y moth, Autographa gamma (L.) (Lepidoptera: Noctuidae). Cooperative Agricultural Pest Survey, Animal and Plant Health Inspection Service, US Department of Agriculture.
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