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Investigations were carried out during two consecutive Rabi seasons of 2014 and 2015 at the Experimental Farm of the Department of Seed Science and Technology, Dr Y S Parmar University of Horticulture and Forestry, Nauni, Solan, Himachal Pradesh, India to study the spatial distribution of Brevicoryne brassicae in cabbage. One month old cabbage seedlings were planted in the field in the month of November during both the years. Distribution pattern of any insect population is an important aspect as it represents the interaction between individuals of the species and their habitat. Spatial distribution is useful for designing efficient sampling programmes for population estimation and development of population models. Spatial distribution is also important to understand the bioecology of the pest and to determine the sampling protocol for that species. In the present study variance to mean ratio (s2/ X),mean crowding (X*), ratio of mean crowding to mean (X*/X), 'k' of negative binomial, Taylor's power equation (s2 = 0.9099X1.55 during 2014 and s2 = 2.9861X1.1949 during 2015), Iwao's patchiness regression and optimum number of samples (Nopt) required to achieve the desired precision were calculated for different densities. Cabbage aphid, B. brassicae appeared in the fourth standard week i.e last week of January( 26.2 aphids/ plant during 2014 and 0.30 aphids/ plant during 2015) and persisted upto thirteenth standard week i.e last week of April ( 18.4 aphids/ plant during 2014 and 18.2 aphids/ plant during 2015) and followed a negative binomial distribution during both years. Optimum number of samples (Nopt) required varied with mean density as well as precision level. The present study will serve as basic information to develop a sampling plan of B. Brassicae in cabbage for its monitoring and management. [ABSTRACT FROM AUTHOR]

Pea leafminer, Chromatomyia horticola (Goureau) is an important pest of many vegetable and ornamental crops. The present investigation was carried out to study the parasitoid diversity of this pest in different agroclimatic conditions of Himachal Pradesh, India. Sixteen species of parasitoids viz. Diglyphus horticola Khan, Diglyphus isaea (Walker), Zagrammosoma sp., Pnigalio sp., Quadrastichus plaquoi Reina and LaSalle, Asecodes erxias (Walker), Closterocerus sp., Neochrysocharis formosa (Westwood), Chrysocharis sp, Chrysocharis indicus Khan, Pediobius indicus Khan (Eulophidae), Opius exiguus (Wesmael), Dacnusa sp. (Braconidae), Cyrtogaster sp., Sphegigaster sp. (Pteromalidae), and Gronotoma sp. (Figitidae) were recorded parasitizing C. horticola in different agro-climatic zones of Himachal Pradesh. Agro-climatic zone II (sub-temperate mid-hills) was the richest in parasitoid diversity (14 species) followed by zone I (11 species), zone III (7 species) and zone IV (4 species) which are characterized by sub-tropical sub-montane, wet temperate high hills and dry temperate high hills, respectively. Shannon diversity index, species richness, species evenness and species dominance varied from 0.69-1.71, 1.39-2.64, 0.50-0.71 and 0.29-0.50, respectively. D. isaea and D. horticola were the dominant parasitoids of C. horticola contributing 41.46-80.15 and 9.16-50.65 per cent of the total parasitization, respectively, in different agro climatic zones. The study highlights the role of different parasitoids in natural control of the leaf miner and will be useful for designing the IPM strategies for the pest. [ABSTRACT FROM AUTHOR]