Insects and arachnids associated with the aerial part of the sesame cultivation (Sesamum indicum L.) in the Experimental and Practice Station of the Faculty of Agronomic Sciences, University of El Salvador

Abstract

The research was carried out from April 2019 to February 2020 at the Experimental Station of the Faculty of Agronomic Sciences of the University of El Salvador, located in the municipality of San Luis Talpa, department of La Paz, El Salvador. The objective of the research was to determine the abundance and richness of insects and arachnids as part of the diversity of arthropods associated with the different phenological phases of the sesame (Sesamum indicum L.) crop. For this, three plots of 100 m2 were established and sampled every fifteen days, using a net and manual collection. Ten sampling sites were taken in a “zig zag” manner, sampling a linear meter in the furrow where each site was located per plot. A total of 1,633 insects were collected, comprising 11 orders, 72 families and 56 genera. The largest population of insects was observed during the flowering and fruiting of sesame. The most abundant genera were Oecleus (Hemiptera: Cixiidae), Carneocephala (Hemiptera: Cicadellidae), Cyrtopeltis (Hemiptera: Miridae), Apis mellifera (Hymenoptera: Apidae), Disony ovata (Coleoptera: Chrysomelidae), Stigmene acrea (Lepidoptera: Arctiidae), Chelonus (Hymenoptera: Braconidae) and Polybia (Hymenoptera: Vespidae). The families Tenebrionidae and Gelechiidae associated with sesame seeds in storage were more abundant. One hundred and sixty-three spiders were collected, identifying 7 families and 17 genera belonging to the order Araneae. The most abundant family was Thomisidae and the most abundant genus Misumena. Phytophagous insects represented 58.85%, pollinators 14.59%, predatory insects 10.18%, spiders 9.08%, parasitoids 6.63% and saprophages 0.68%. The most abundant food guild was Picadores - suckers with 66.04%, external defoliators 19.96%, primary carpophagi 2.37%, leaf miners 1.89%, seed borers 0.28%, and 9.46% of external defoliators and primary carpophagi. The Margalef diversity index (Dmg), Shannon-Wiener index (H ‘) and Simpson index (D) were determined. The highest richness of insects (Dmg = 7.95), equity (H´ = 3.39) and lowest dominance (1-D = 0.96) were obtained in the fruiting phase. The relationship between the variables under study (p <0.05) indicates that the richness and abundance of insects and spiders is influenced by the phenological phases of sesame cultivation