Comparative Diversity and Seasonal Occurrence of Insect Pest Complex in Litchi Ecosystem from Two Different Agro-climatic Sub-regions of Eastern Himalayan Zone of India

Abstract

A study was conducted to find out the diversity and seasonal occurrence of different insect pests in litchi orchards of two different agro-climatic sub-regions, i.e., sub-region II and sub-region V of Agro-Climatic Zone II (Eastern Himalayan Region) of the country during March, 2022 to February 2024. The study has documented a total of 16 species of insect pests under 16 different families infesting litchi plants from these two sub-regions of Zone II. Among them, six were Coleopteran pests, two were Hemipteran, and six were Lepidopteran pests, and one pest from each of the Diptera and Sarcoptiformes orders was in the species assemblage. The cumulative population of different leaf- and stem-infesting insect pests was 1763 individuals/120 sweeps in sub-region II, which was drastically higher than that of sub-region V (i.e., total population of 581 individuals/120 sweeps). However, the sub-region V was characterized by a greater diversity and richness in the species community than the sub-region II. Furthermore, in sub-region V, the species are more evenly distributed in the community, with less dominance by a single or few species as compared to sub-region II. The incidence pattern of different insect pests suggested higher insect pest incidence from the 1st fortnight of March to the 1st fortnight of June in sub-region V and from the 1st fortnight of May to the 1st fortnight of June in sub-region II. These outcomes provide valuable insights in order to adopt appropriate pest management schedules, typically during the most critical period of pest incidence.