Aspectos biológicos de Planococcus citri (Pseudococcidae) em roseira e compatibilidade dos predadores Cryptolaemus montrouzieri (Coccinellidae) e Chrysoperla externa (Chrysopidae) no controle dessa cochonilha

Abstract

The floriculture has been consolidating as an economic activity of great relevance. In this scenario, roses are one of the most produced and commercialized cut flowers in the world. However, the incidence of pests in roses crops can become an obstacle to production. Among them, the mealybug Planococcus citri has assumed economic importance, occurring in large populations on cultivated roses in Minas Gerais and Ceará states, Brazil. Due to the absence of synthetic insecticides registered for the control of P. citri in ornamental plants in Brazil, and the limitations of these products for mealybugs control, the biological method has been presented as a promising strategy for population reduction of these organisms. The exotic predator, Cryptolaemus montrouzieri, and the native one, Chrysoperla externa, exhibit great potential in the control of mealybugs of the family Pseudococcidae. Thus, the aims of the present study were to evaluate aspects of the biology of P. citri, still unknown in rose plants in Brazil, to evaluate the predatory capacity of C. montrouzieri and C. externa on P. citri, to investigate the behaviour of the predators separately, and the occurrence of intraguild interaction and behaviour when both predators are combined. In the study on the biology of P. citri, all the development and reproductive characteristics of the mealybug on rose leaflets were monitored in laboratory. The predatory capacities of C. montrouzieri adults and third instar larvae of C. externa were evaluated on the first, second and third instars of P. citri and on adult females. The behaviour of predators was investigated in all treatments by the Etholog 2.2 program. The intraguild interaction between the predators was analyzed against first instar nymphs and adult females of P. citri and behaviour of the predators was observed. P. citri develops rapidly in rose bush compared to its development associated with other ornamental plants. Adults of C. montrouzieri and third instar larvae of C. externa present a decreasing in predation with the development of P. citri. C. montrouzieri shows higher consumption on the young stage of P. citri but on adult females does not present difference in relation to C. externa. Adults of C. montrouzieri and third instar larvae of C. externa do not exhibit significant intraguild interaction when confined to adult females of P. citri. However, compared to first instar nymphs predators interact positively resulting in a synergistic consumption. The behaviour of C. montrouzieri and C. externa is influenced by the development stage of P. citri and by the presence of a competitor.