Nematóides entomopatogênicos como controladores biológicos de cigarrinhas do gênero Mahanarva (Hemiptera: Cercopidae)

Abstract

The spittlebugs belonging to the genus Mahanarva cause damage to the Poaceae family cultures, like signal grass, elephant grass and sugar cane, by the sap feeding on roots (immature phase) and leaves (adult phase). With the increase demand to reduce use of chemical insecticides for the insect pests’ control, comes the need to develop new control methods. In this scenario, the biological control gains highlight and in the spittlebugs case, the entomopathogenic nematodes (EPNs) are potential control agents, exploring the soil surface, the same pest environment while it feeds on roots. Thus, with the aim to know the EPNs’ action and to screening strains of these pathogens against the leaf spittlebug, Mahanarva spectabilis, and the root spittlebug, Mahanarva fimbriolata, experiments were conducted with various EPNs strains over different insect development phases. In two experiments M. spectabilis and M. fimbriolata nymphs were exposed to the pathogens, in laboratory and greenhouse conditions, and then were screened the more pathogenic strains to each pest species. Following, were evaluated the efficiency of four application methods of EPNs (pippeting, spray over nymphs with and without froth and infected host cadaver) over the leaf spittlebug, at greenhouse. At last, were evaluated the efficiency of an EPN species over eggs and adults of the leaf spittlebug. All tested strains are pathogenic to the spittlebugs nymphs causing 40-92% and 38-90% mortality at laboratory and 14-71% and 48-72% at greenhouse, to M. spectabilis and M. fimbriolata, respectively. The more efficient application methods were spray over nymphs with froth and infected host cadaver, with no difference because the concentrations and strains. Observations showed that don’t occurs eggs infection by EPNs in leaf spittlebugs. The leaf spittlebug adults not were infected by the EPNs, and no egg reduction were observed. The most pathogenic EPNs strains were Steinernema riobravis, S.feltiae and Heterorhabditis amazonensis RSC1 to M. spectabilis and S. feltiae, S. riobravis, H. baujardi LPP7 and S. carpocapsae to M. fimbriolata. Thus I conclude that entomopathogenic nematodes can be utilized to control Mahanarva genus spittlebugs, and can be inserted in integrated pest management programs, should to be applied over nymphs exclusively, sprayed over the froth or through infected host cadevers.