Caracterização e patogenicidade de fungos entomopatogênicos isolados do percevejo-bronzeado do Eucalipto, Thaumastocoris peregrinus (Hemiptera: Thaumastocoridae)

Abstract

The area of Eucalyptus plantations in the world has increased in recent decades. In 2011 the total area of eucalyptus plantations in Brazil was 4.873.952 ha. The native insects are a major problem in eucalyptus plantations in Brazil, but in recent years, new pests have been introduced and causing widespread crop losses. In May, 2008,Thaumastocoris peregrinuswas detected first time in Brazil, in São Francisco de Assis, State of Rio Grande do Sul. This pest reduces and affects the productivity of eucalyptus plantations. Nymphs and adults feed by sucking the leaves, causing chlorotic spots, which develop inbronzed look. The development of microbial control using microrganisms, as entomopathogenic fungi, as an option. Testsevaluatingcommercial bioinsecticides and isolating native fungi speciesfrom the natural epizootics in the field,are an important tool for its control. Nowadays there is a few control alternatives for the problem caused by this pest in eucalyptus plantations. The present work aimed to obtain isolates of entomopathogenic fungi from dead individuals of T. peregrinus collected in field; selecting isolatesand evaluated them considering characteristics of biology (growth rate and general appearance of the colony) morphology (size and shape of spores and the presence / absence of specialized structures) and molecular; verify the sensitivity of fungi isolate against potential insecticides used to eucalyptus bronze bug control; evaluate colonization of fungi isolated when inoculated directly into the bronze bug using scanning electron microscopy. Many fungi were isolated, but for practical purposes only two were chosen for the development work. All fungi tested were able to cause insect mortality. All fungi have shown significant sensitivity to the insecticidesimidacloprid and thiamethoxam. The identity of each fungus as determined usingtwo DNA regions (ITS-5.8S rDNA, andα-elongase) and they wereidentified asFusarium proliferatumandPaecilomyces cateniannulatus (=Isaria cateniannulata). After the fungi identification, a test to evaluate a possible phytopathogenicity was carried out since many species of genus Fusarium are phytopathogenic in different agricultural crops. From the isolates of F. proliferatum, the bioassay was carried out , applying suspensions of the fungus at concentrations of 106 spores/mL, by sprayed in the leaves and soak the rootsof plants of sugarcane, maize, tomato and Eucalyptus. The experiment was carried out in a greenhouse and evaluated daily by 45 days. During this time, it not observed any disease symptoms in all plants tested.