Pieris rapae (L.)
Taxonomic placing: Insecta, Holometabola, Lepidoptera, Pieridae.
Morphology: The adult is about 15 mm long, the forewings are white with 1-2 round black spots and a large anterior black area, the underside of the hindwings is pale yellow. The larvae are very hairy, green-grey with black dots and yellow lateral and dorsal stripes, the head is blackish, body length up to 30 mm.
Geographical distribution: Europe, The Middle East, Southern Asia, North America and Australia.
Host plants: Brassicaceae, such as cabbage, radish and horseradish.
Life history: Females, which feed on nectar and live for several weeks, lay several hundred eggs singly on the host foliage and the hatched larvae are solitary. The pest, which is active the year around, raises 7-8 annual generations.
Economic importance: Due to its solitary nature and tendency to invade the densely packed leaves of cabbage, the larvae may not be noticed till some damage had been done. They excrete much contaminating fecal material that reduces the market value of the product.
Management
Monitoring: The green larvae, which may be hiding within cabbage heads, are difficult to find and may require some searching.
Host resistance: Cultivars with dark green, glossy or red leaves may be partially resistant to P. rapae, although attractive to other pests.
Biological control: The pest is attacked by the braconid parasitoids Cotesia glomerata (L.) (formerly placed in the genus Apanteles), Cotesia rubecula Marsh and Meteorus versicolor (Wesmael), and by Pteromalus puparum (L.) Pteromalidae). These parasitoids (especially C. glomerata) may kill many (up to 80%) pests. The carabid Harpalus rufipes DeGeer and Anthocoridae were the major predators of P. rapae In England. Applications of a product of Bacillus thuringiensis (Bt) and of entomopathogenic fungi provided about 20% pest control. A naturally occurring granulosis virus may occasionally kill large pest numbers.
References
Cai, J., Ye, G.-y. and Hu, C. 2004. Parasitism of Pieris rapae (Lepidoptera: Pieridae) by a pupal endoparasitoid, Pteromalus puparum (Hymenoptera: Pteromalidae): effects of parasitization and venom on host hemocytes. Journal of Insect Physiology 50: 315–322.
Dempster, J.P. 1969. Some effects of weed control on the numbers of the small cabbage white (Pieris rapae L.) on Brussels sprouts. Journal of Applied Ecology 6: 339-345.
Dickson, M.H. and Eckenrode, C.J. 1980. Breeding for resistance in cabbage and cauliflower to cabbage looper, imported cabbageworm, and diamondback moth. Journal of the American Society of Horticultural Science 105: 782-785.
Harcourt, D.G. 1966. Major factors in survival of the immature stages of Pieris rapae (L.). The Canadian Entomologist. 98: 653-662.
Sabbour, M.M. and Sahab, A.F. 2005. Efficacy of some microbial control agents against cabbage pests in Egypt. Pakistan Journal of Biological Sciences 8: 1351-1356.
Şengonca, Ç. And Peters, G. 1993. Biology and effectiveness of Apanteles rubecula Marsh. (Hym., Braconidae), a solitary larval parasitoid of Pieris rapae (L.) (Lep., Pieridae). Journal of Applied Entomology 115: 85-89.
Van Driesche, R.G. 1988. Survivorship patterns of larvae of Pieris rapae (L.) (Lepidoptera: Pieridae) in Massachusetts kale, with special reference to mortality due to Apanteles glomeratus L. (Hymenoptera Braconidae). Bulletin of Entomological Research 78: 397–405.
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