Agrotis ipsilon (Hufnagel)
Taxonomic placing: Insecta, Holometabola, Lepidoptera, Noctuidae.
Common name: Black cutworm.
Geographical distribution: Almost cosmopolitan, CIE Map #261, 1969.
Host plants: Seedlings of most crops, including legumes, crucifers, Solanaceae and cotton in the Middle East.
Morphology: The specific name of the pest (ipsilon) derives from the markings on the adult forewings, which resemble the Greek character “ipsilon”. Its common name (“cutworm”) is due to the nature of the damage, the cutting off of seedlings at ground level, and the dark background coloration of the larval integument.
Life history: Female adults, which are reproductively immature on emergence, begin oviposition within a week and survive for about another week. During their gravid period eggs are deposited singly or in small clusters, on the underside of leaves, near ground level. A female may lay up to 1900 eggs during its lifetime. The larvae disperse after the first molt and remain solitary for the rest of their lives, residing in the soil during day, coming up to feed at night.
Seasonal history: The pest is a migratory species, with no seasonal diapause. The duration of each generation is one-two months, depending on environmental conditions. In Israel the pest has 4-5 generations, of which those with most potential to cause damage are during autumn (November-December) and spring (February-March). Early autumn rains (e.g. high humidity) and mild temperatures are conducive to population increase. The autumn population in Israel is presumably bolstered by migrant adults. Infestations in Syria are higher in years with high rainfall.
Economic importance: Larvae commonly feed on seedlings, cutting off their stems at ground level, which topples them. Additionally, the larvae may feed on roots, thus occasionally causing great damage in newly planted fields (e.g. cotton) early in the season.
Management
The occasional appearance of black cutworm populations poses a logistic problem for preventive measures, especially as the larvae reside in the soil, making detection difficult until damage had revealed their existence. Control measures are difficult because of the inaccessible location of the larvae to some forms of chemical applications. One preventive measure is sanitation, the removal of weeds and volunteer plants from previously-damaged fields and their surroundings, and deep ploughing if populations recur. Adults on the wing can be monitored by pheromone trapping. First damage may usually be expected about 2 weeks after peak flight.
Chemical control: Spray applications may be directed towards first instar larvae while they are still feeding on the underside of foliage, or else granular insecticides can be applied onto the soil. Moistened poison bait may be mixed with the organophosphates trichlofon and parathion, or the carbamate carbaryl, and broadcast in the field at 10 kg/ha, preferably in the evening.
Biological control: Natural enemies are not reliable for black cutworm control, mostly due to the sporadic appearance of the pest and the inability of seedlings to compensate for any incurred damage.
References
Hill, D.S. 1983. Agrotis ipsilon (Hfn.). In: Agricultural Insect Pests of the Tropics and Their Control, 2nd Edition, pp. 357-358. Cambridge University Press, Cambridge.
Rings, R.W., Arnold, F.J. and Johnson, B.A. 1975. Host range of the black cutworm on vegetables: A bibliography. Bulletin of the Entomological Society of America 21:229-234.
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