Population dynamics of cabbage webworm, Hellula undalis and diamondback moth, Plutella xylostella (Lepidoptera:Crambidae : Plutellidae) at Fayoum Governorate

The lepidopteran is an insect of great economic importance; it includes many species whose larvae feed on important agricultural crops and cause serious damage to the valuable products. Many species are also associated with forest vegetation and ornamental plants,posing serious damage as defoliators. During the field survey, different immature stages viz., eggs, larva, pupa, and adult, of the speciesHellula undalis (Fabricius) and Plutella xylostella (L.) (Lepidoptera: Crambidae: Plutellidae), were collected in the field from detailed accounts on different life history aspects of the species. Results: H. undalis larvae were recorded on cabbage plants in summer plantations during 16th April and 27th March of the 1st and 2nd seasons and fluctuated in their density until harvesting crops. It had only one peak with 44 and 33 individuals/30 leaves for the 1st and 2nd seasons, respectively. The pest completely disappeared during winter plantations. Diamondback moths were found on cabbage crops in summer and winter plantations, but they were abundant in winter plantations during both study seasons. In the winter plantation, the total population recorded two peaks during 16th November and 16th December with 8 and 14 individuals/30 leaves in the first season, and 10th and 30th January with 36 and 38 individuals/30 leaves in the second season.