Insights from Insect Diversity and Functional Roles in Sorghum Pest Management: A Case Study from Northern Sumatera, Indonesia

Abstract

This study, conducted in Lalang Village, Tebing Tinggi, Indonesia, from August to October 2021, aimed to investigate the insect diversity and functional roles relevant to Sorghum (Sorghum bicolor) monoculture. Employing a purposive random sampling method, we utilized four trapping techniques (yellow sticky trap, pitfall trap, light trap, and sweep net) according to standard protocols. Analysis revealed insects recorded from S. bicolor, representing seven orders (Coleoptera, Diptera, Hemiptera, Hymenoptera, Lepidoptera, Odonata, Orthoptera), 28 families, 32 species, totaling 10,022 individuals. We identified 32 species, classified into four insect functional groups: parasitoids (3 families), pollinator (1 family), predators (12 families), and pests (12 families). The Importance Value Index (IVI) values were compared among the functional groups, collectively indicating that Apis mellifera (Order Hymenoptera Family Apidae) was the most prevalent pollinator, followed by parasitoids comprising three families (Ichneumonidae, Ceraphronidae, and Tachinidae). Pest species, including Agrotis ipsilon, Helicoverpa armigera, Mythimna separata, Eublemma silicula, and Spodoptera frugiperda, exhibited the highest IVI value of 27.14%. Predators were led by Podisus maculiventris (Family Pentatomidae) with an IVI value of 9.19%. Pests dominated with an abundance of 62.09%, followed by predators (31.49%), pollinators (5.98%), and parasitoids (0.44%). The t-test results were significant across day after sowing (DAS) and different traps with scores such as t-day after sowing (t-DAS)=22.051; t-yellow sticky trap (t-YST)=12.311; t-pit fall trap (t-PFT)=10.271; t-light trap (t-LT)=12.403; t-sweep net (tSN)=12.99, where h<0.01). Biological indices indicated a low species richness (R1=2.11), high species evenness (E=0.824), and moderate Shannon-Wiener diversity score (H’=2.27). Understanding the functional roles of these insects in S. bicolor cultivation emphasizes the necessity of integrated pest management for effective pest control strategies. Our findings stress the importance of biodiversity conservation and effective management practices for sustainable sorghum cultivation in Northern Sumatera, Indonesia.