Potencial de crisopídeos como predadores do psilídeo-deconcha Glycaspis brimblecombei (Hemiptera: Aphalaridae) em eucalipto

Abstract

Several native and exotic pests, among which stands out the shell psyllid, Glycaspis brimblecombei, which has caused enormous losses in forest systems, seriously threaten the productivity of eucalyptus crops. In Brazil, the occurrence of green lacewings in eucalyptus plantations is common, such as Ceraeochrysa cubana and Chrysoperla externa, however, little is known about bioecological and behavioral aspects of predators associated with the Red-Gum- Lerp. Thus, the objective of this work was to evaluate the predatory behavior of two species of abundant and frequent green lacewings in these crops, as well as the predatory capacity, functional response and biology of one of them, when eggs and each of the stages of development of the psyllid are made. The behavior was studied for the 1st, 2nd and 3rd ínstars of Chrysoperla externa and Ceraeochrysa cubana, through monitoring with the use of Boris software. This study was carried out when exposed to eggs and nymphs of 1°, 2nd and 3rd, and 4th and 5th ínstar of the shell psilyde, maintained at 25±1°C, RH of 70±10% and photophase of 12h. Predatory capacity, biology and functional response were studied for C. externa fed with eggs and nymphs of G. brimblecombei and with eggs of Ephestia kuehniella as control. The study of predatory capacity was conducted with larvae of 2º and 3º instares of C. externa supplied with nymphs of 2nd and 3rd Red Gum Lerp instars offered in naturally infested eucalyptus leaves. For biology, newly hatched larvae were transferred to containers containing eucalyptus leaves naturally infested with eggs and nymphs of G. brimblecombei. The duration of the instars and phases of the development of the predator were followed up until the emergence of the adults. Both experiments were carried out at room temperature (~26 °C) and photophase of ~12 hours. For the functional response, 3rd instar larvae were used, with 24 hours after ecdysis, supplied with Eggs of G. brimblecombei, at densities of 1, 2, 4, 8, 16 and 32 eggs per larva of the predator. This experiment was carried out at 25±1°C, RH of 70±10% and photophase of 12 h. It was found that C. externa and C. cubana, in their different instars, present different behavioral parameters and both can feed on eggs and nymphs in the initial instars (1st, and 2nd and 3rd) of the Red Gum Lerp. The life cycle of C. externa supplied with eggs and nymphs of the Red Gum Lerp that the psillyd constitutes an adequate food resource for this green lacewings. Third-instar larvae of C. externa are effective in controlling eggs and nymphs of 1°, 2° and 3° instar of the Red Gum Lerp, especially at lower densities of the pest. In general, the results obtained in the present investigation point to C. externa as a biological agent option for the control of eggs and early instars of G. brimblecombei in eucalyptus crops. With regard to C. cubana, this study showed it to be a potential agent for the control of the psyllid, requiring further studies on this predator.