Hellula undalis Fabricius
Taxonomic placing: Insecta, Holometabola, Lepidoptera, Crambidae.
Common name: Cabbage Webworm.
Geographical distribution: Europe, Asia and the Pacific Region.
Host plants: Many wild and cultivated Brassicaceae (Cruciferae), including broccoli, cabbage, cauliflower and radish.
Morphology: The larvae (caterpillars) are yellow/brown, with longitudinal dark pink lines; head black, length about 15 mm. Forewingss of adults grey to brown-yellow, with small brown spots and white transverse lines, hindwings light brown, body length 15-18 mm.
Life cycle: The females, which are active in evenings and at night, place their eggs (about 75-250/female) singly, or in groups of 2-3 on the inner tissues of host plants. The hatching larvae bore into the stems of growing shoots or growing points, weaving webs into which they place their frass. Development of a generation requires about 4-5 weeks at 27°C. They pupate in the soil within webbed cocoons that include soil particles. Adults are short-lived and the pest can complete 7-8 annual generations.
Economic importance: This webworm is a major pest of crucifer crops in the tropics and subtropics, especially affecting cabbage and radish. It is very harmful to young plants, stunting or killing them. Without any control measures yield losses of 30-100% were reported from India and the Philippines.
Management
Monitoring: Regular examinations of young plants in nurseries and after transplanting, looking for the larvae, their webs, frass and any damage symptoms. Male activity can be determined in the field by using a sticky trap baited with two laboratory-reared one-day old virgin females.
Horticultural methods: Using clean planting materials and transplanting only healthy, vigorous insect-free seedlings. Uprooting and burning of any cabbage and other related plant debris, and crop rotation. Protecting seedling beds and greenhouses with close mesh nets or screens.
Chemical control: Carbamates and organophosphates controlled the moth when applied at first pest appearance on plants. The moth was highly sensitive to various Bacillus thuringiensis formulations.
Biological control: Parasitoids of the families Braconidae and Ichneumonidae attacked the pest in Malaysia, as well as the ant Solenopsis geminate (F.). Infection with a Microsporidium caused 80% mortality in the laboratory.
References
Harakly, F. A. 1968. Biological studies on the cabbage webworm, Hellula undalis F. (Lepidoptera: Crambidae-Pyraustidae). Bulletin de la Société Entomologique d’Egypte 52: 191-211.
Mewis, I., Kleespies, R.G., Ulrichs, C. and Schnitzler, W.H. 2003. First detection of a microsporidium in the crucifer pest Hellula undalis Lepidoptera: Pyralidae)—a possible control agent? Biological Control 26: 202–208.
Sivapragasam, A., Ahmad, A. and Abdullah,R. 1996. Sampling adult male populations of Hellula undalis (Lepidoptera: Pyralidae) in cabbage using virgin-females baited sticky traps. In: Sivapragasam, A., Loke, W.H., Hussan, A.K. and Lim, G.S. (eds) The Management of Diamondback Moth and Other Crucifer Pests. Proceedings of the Third International Workshop, Kuala Lumpur, Malaysia: 335-338.
Sivapragasam, A. and T. H. Chua, T.H. 1997. Natural enemies for the cabbage eebworm, Hellula undalis (Fabr.) (Lepidoptera: Pyralidae) in Malaysia. Research Population Ecology 39 : 3-10.
Srinivasan, R. and Hsu Yun-Che. 2008. Susceptibility of major lepidopterans to δ-endotoxins and a formulation of Bacillus thuringiensis (B.t.) on vegetable brassicas in Taiwan. Biocontrol Science and Technology 18: 935-939.
Yabaş, C. and Zeren, O. 1992. Studies on the chemical control of Hellula undalis F. in the eastern Mediterranean region. Proceedings of the Second Turkish National Congress of Entomology, 335-341.
Youssef, K.H., Hammad, S.M. and Donia A.R. 1973. Studies on biology of the cabbage webworm, Hellula undalis (F.) (Lepidoptera: Pyraustidae). Zeitschrift für Angewandte Entomologie 74: 1-6.