PEST MANAGEMENT Characterization of Feeding Injuries Caused by Ceresa nigripectus Remes Lenicov (Hemiptera: Membracidae) on Alfalfa Stems TP GROSSO 1 , MI MERCADO 2 , GI PONESSA 2 , LR CONCI 1 , EG VIRLA 3 1 Centro de Investigaciones Agropecuarias (CIAP), Instituto de Patología Vegetal (IPAVE), INTA, Córdoba, Argentina 2 Área Botánica, Instituto de Morfología Vegetal, Fundación Miguel Lillo, San Miguel de Tucumán, Argentina 3 Instituto de Entomología, CONICET and Fundación Miguel Lillo, San Miguel de Tucumán, Argentina Abstract Keywords Feeding injuries, plant wound response, sap feeders Correspondence MI Mercado, Área Botánica, Instituto de Morfología Vegetal, Fundación Miguel Lillo, Miguel Lillo 251, San Miguel de Tucumán, T4000JFE, Argentina; mainesmer@yahoo. com.ar Edited by Jorge Braz Torres – UFRPE Received 22 May 2015 and accepted 2 December 2015 * Sociedade Entomológica do Brasil 2015 Piercing-sucking insects cause mechanical and physiological injury to plants. Ceresa nigripectus Remes Lenicov is a pest of alfalfa in subtropical regions of South America and a carrier of the ArAWB phytoplasma. The aim of this study was to determine the feeding habits of this treehopper and to describe the effects of the feeding injuries on stem vascular tissues in alfalfa. Adults and nymphs of C. nigripectus inserted their stylets repeat- edly girdling the stem. One week after feeding, alfalfa stems exhibited numerous feeding canals with salivary deposits, most of which reached the phloem. Two weeks after feeding, cortex and phloem cells next to the salivary sheath collapsed, mature tracheal elements became sparse and appeared with an increased cross-section area, and phenolic compounds increased in cells and cell walls compared to undamaged plants. Three weeks after feeding, an annular callus, formed by abnormal cell division and hypertrophy of preexisting cortex and vascular cambium cells, ap- peared immediately above the stem girdle. Parenchyma cells from the outer layers of the callus differentiated to form secondary anomalous amphicribal bundles in the wound. The aerial parts above the stem girdle eventually withered and died. Introduction Alfalfa is an essential crop in temperate regions in the USA, Canada, Italy, France, China, and southern Russia in the Northern Hemisphere, and in Argentina, Chile, South Africa, Australia, and New Zealand in the Southern Hemisphere. It represents the best source of hay for domestic use, silage, and it is used for conservation and recovery of productive soils (Yuegao & Cash 2009). The feeding behavior of Hemiptera-Auchenorrhyncha has been extensively studied because of two reasons: the direct damages caused on their hosts and transmission of patho- gens to plants (Backus 1985, Miles 1989, Nault 1997, Andersen et al 2002, Godoy et al 2006). Piercing-sucking feeding causes mechanical damage, facilitating the entry of opportunistic microorganisms, and physiological effects by the deposited saliva (Ecale & Backus 1995a, Shackel et al 2005, Savatin et al 2014). Membracidae (Hemiptera: Auchenorrhyncha: Cicadomorpha) is a large family that includes about 3500 species worldwide (Deitz et al 2011). Remes Lenicov (2014) listed 140 species from 55 genera of occurrence in Argentina, where the subfamily Smiliinae is the most diverse with 63 species. Membracidae are typically phloem sap feeders (Jordan 1952, Tjallingii 1994, Gajalakshmi & Jayakumar 2011). Similar to other Hemiptera, these insects produce at least two types of salivary secretions. The first one is a watery type of saliva, a vehicle primarily for digestive enzymes se- creted during ingestion, accomplishing the digestion of sap and liquefying plant cellular contents and cell walls (Frati et al 2006). The second type of saliva is lipoproteinaceous and is secreted, while the stylets are penetrating the plant tissues. Neotrop Entomol DOI 10.1007/s13744-015-0357-7