Agrotis segetum Denis and Schiffermüller
Common name: Turnip moth.
Taxonomic placing: Insecta, Holometabola, Lepidioptera, Noctuidae.
Geographical distribution: Europe, Africa and Asia, CABI Pest map #490 (1987).
Host plants: Many garden and fruit trees crops, as well as weeds.
Morphology: Forewings yellow-brown with wavy, dark stripes and several dark spots, hindwings whitish with yellow veins, body about 20 mm long. Larva initially white-reddish, with 3 pairs of prolegs, later becoming dark-grey, with 5 pairs of prolegs, about 40-50 mm long, a reddish head and two parallel longitudinal stripes. .
Life history: A female lays several hundred eggs on various plants. The emerging larvae initially feed above ground, then move underground to consume the roots of various plants. The young stages are very susceptible to prolonged high humidity in the soil. In the Middle East the pest, which is a strong flier, raises five annual generations.
Economic importance: A serious pest of root vegetables and cereals. The feeding of young larvae on leaves produces “windowpanes”, where only the lower epidermis has remained. Larger larvae “cut off” the petioles of small seedlings, hence “cutworms”. Large holes occur on root crops at the soil surface, and damage to potatoes tubers is only discovered at harvest. Red beet and carrot losses came to 20-30% in Denmark.
Management
Monitoring: Pheromone and light traps are widely used. Activity in the field is confirmed when finding leaves with holes or if they had dropped after being cut at the bases of their stalks, or by holes on stems and on roots at the soil surface, and by the presence of leaf pieces partly pulled into the soil. Entire plants may drop and deep holes occur at and above the soil surface. Forecasting turnip moth attacks is difficult due to variable local weather conditions.
Horticultural control: Fallowing or deep ploughing before sowing may starve the larvae, and watering during or slightly after moth swarming reduced their damage by up to 80%. Infested plant parts and tubers should be destroyed by burning or deep burial and nearby weeds are to be removed. Baits based on sweetened bran, finely spread, can reduce the populations.
Mating disruption: This approach was tried in Sweden.
Chemical control: Field sprays with the organochloride insecticide endosulfan (which is being phased out of use) sometimes controlled the pest. Treatments are to be applied when the young larvae are still exposed, on plants above ground.
Biological control: Egg parasitoids of the genus Trichogramma (Trichogrammatidae) provide some control. Entomopathogenic nematodes killed as many pest larvae as did a pesticide. Studies in South Africa suggest that maize that had been engineered to contain the Bacillus thuringiensis Berliner toxins (Bt-maize) do not have a significant effect on the pest. Baculoviruses are very virulent to the pest, providing over 90% kill. A very lethal entomopathogenic fungus was once found in Sweden.
References
Dunkelblum, E. and Gothilf, S. 1985. Sex attractant blends for field trapping of Agrotis segetum males (Lepidoptera: Noctuidae) in Israel and Germany. Zeitschrift für Naturforschung 40: 272-277.
El-Salamouny, S., Lange, M., Jutzi, M., Huber, J. and Jehe, J.A. 2003. Comparative study on the susceptibility of cutworms (Lepidoptera: Noctuidae) to Agrotis segetum nucleopolyhedrovirus and Agrotis ipsilon nucleopolyhedrovirus. Journal of Invertebrate Pathology 84: 75–82.
Erasmus, A., Van Rensburg, J.B.J. and Van Den Berg, J. 2010. Effects of Bt maize on Agrotis segetum (Lepidoptera: Noctuidae): a pest of maize seedlings. Environmental Entomology 39: 702-706.
Esbjerg, P. and Sigsgaard, L. 2014. Phenology and pest status of Agrotis segetum in a changing climate. Crop Protection 62: 64-71.
Lössbroek, T.G. and Theunissen, J. 1985. The entomogenous nematode Neoaplectana bibionis as a biological control agent of Agrotis segetum in lettuce. Entomologia Experimentalis et Applicata 39: 261–264.
Loefstedt, C. and Loefqvist, J. 1985. Control of the turnip moth Agrotis segetum (Lepidoptera, Noctuidae) by mating disruption. Vaxtskyddsnotiser 49: 45-48 (in Swedish).
Steenberg, T. and Øgaard, L. 2000. Mortality in hibernating Turnip moth larvae, Agrotis segetum, caused by Tolypocladium cylindrosporum. Mycological Research 104: 87-91.
Svensson, G.P. (and 7 co-authors) 2001. Mating disruption in Agrotis segetum monitored by harmonic radar. Entomologia Experimentalis et Applicata 101: 111–121.
Zethner, O. 1977. Losses caused by cutworms (Agrotis segetum SCHIFF.) and approaches to their control in Denmark. Proceedings 1977 British Crop Protection Conference - Pests and Diseases, pp. 271–277.