Estudos das interações de Helicoverpa armigera (HÜBNER, 1805) ao predador Chrysoperla externa (HAGEN, 1861) e fungos entomopatogênicos

Abstract

The management of Helicoverpa armigera (Hübner 1805) (Lepidoptera: Noctuidae) in Brazil is mainly based on the use of chemical, biological insecticides and Bt plants, however, there are gaps about the possible interactions between the use of these practices and the agents of natural control, such as lacewings and entomopathogenic fungi. The aim of this study was to evaluate the interactions between the predator Chrysoperla externa (Hagen 1861) (Neuroptera: Chrysopidae) and the entomopathogenic fungi Beauveria bassiana (Bals.) Vuillemin (isolado ESALQ PL63), Metarhizium anisopliae (Metchnikoff) and Metarhizium rileyi (Farlow) Samson (isolado UFMS 03), for the control of H. armigera. The experiment was subdivided into 3 bioassays, all conducted under laboratory conditions, under T°C 25 ± 1°C, 70 ± 10% RH and 12 hours photoperiod (light and dark = L: D), with the following treatments. (P): control (sterile distilled water + 0.001% Tween80®) (T1); B. bassiana (T2); M. anisopliae (T3) and M. rileyi (T4), applied through an adapted Potter tower at concentrations (C): (1 × 107; 1 × 108 and 1 × 109 conidia mL-1) using two methodologies of Application (A): Direct application (DA) and dry film (DF). For the 1st bioassay the virulence of B. bassiana (isolado ESALQ PL63), M. anisopliae (isolado ESALQ E9) and M. rileyi (isolado UFMS 03) on 1st, 2nd, 3rd, 4th and 5th instar caterpillars of H. armigera. The 2nd bioassay verified the selectivity of these fungi on larvae of 1st, 2nd, 3rd of C. externa. The 3rd bioassay evaluated the interaction of these microorganisms with C. externa by applying treatments on eggs (<24 hours) and H. armigera caterpillars (1-3 mm) and offered to 3rd instar larvae of the predator at different times (0, 24 and 48 HAA). The three bioassays used (DIC) o experimental design, with factorial arrangement (4 × 3 × 2), consisting of 4 treatments (P), 3 concentrations (C) and 2 application methodologies (A). Data were subjected to analysis of variance (ANOVA) and comparison of means by Tukey test at 5% probability, using the Rbio software. The results of the 1st bioassay indicate low virulence of isolados tested on H. armigera, regardless of concentrations or application methods. The 2nd bioassay showed that M. anisopliae (isolado ESALQ E9) and M. rileyi (isolado UFMS 03) presented selectivity to the 1st, 2nd, 3rd instar larvae of C. externa; and B. bassiana (isolado ESALQ PL63) provided low mortality over the predator's three larval stages (120 HAA). The results of the 3rd bioassay demonstrate that isolados at the concentrations and exposure methodologies tested do not interfere with the biological development and predatory potential of C. externa on H. armigera eggs and larvae at different exposure times. It is possible to use C. externa and entomopathogenic fungi B. bassiana (isolado ESALQ PL63), M. anisopliae (isolado ESALQ E9) and M. rileyi (isolado UFMS 03) due to the selectivity of these isolados to the three larval instars. of green lacewing and the positive interaction between entomopathogenic fungi and C. externa larvae in the control of eggs and small larvae of H. armigera.