Potencial do predador Podisus nigrispinus (Dallas) e do parasitoide Tetrastichus howardi (Olliff) no controle de Helicoverpa armigera (Hübner)

Abstract

Brazil is one of the world's largest producers of soybeans, reaching new production records every year. However, this increase in production may be threatened due to the phytosanitary problems that Brazilian producers are facing, especially the occurrence of pest insects that cause crop damage, compromising productivity. Among the insect pests in the soybean crop, the Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) had its first registration in the agricultural year 2012/2013 in the fields of production, causing great damage in several crops. The biological control of H. armigera using conservation tactics or the increase of natural enemies in agroecosystems is a reality that needs to be investigated and explored under Brazilian conditions, being an important tool to control this pest. Therefore, due to the necessity of studies on the natural enemies of this pest, this work aims to verify the potential of the predator Podisus nigrispinus (Dallas) (Hemiptera: Pentatomidae) and the parasitoid Tetrastichus howardi (Olliff) (Hymenoptera: Eulophidae) of H. armigera. For this, biological aspects of P. nigrispinus fed H. armigera under laboratory conditions were evaluated, as well as the ability of P. nigrispinus to predate H. armigera caterpillars in the field, in the soybean crop. In relation to the T. howardi parasitoid, it was evaluated the parasitism in pupae and H. armigera caterpillars, as well as the possibility of the parasitoid to locate and parasite H. armigera pupae under field conditions in the soybean crop. The results found in this work show that H. armigera is a nutritionally adequate prey, possessing the necessary requirements to promote the development and reproduction of P. nigrispinus in a satisfactory way, being able to be used as food in the mass creations of this predator. In field, in the soybean crop, adult females and fifth instar nymphs of P. nigrispinus preyed 2.26 and 1.73 caterpillars / day of H. armigera, respectively. Tetrastichus howardi successfully parasitized H. armigera pupae in the laboratory. The parasitism of T. howardi on caterpillars was not efficient, but it can occur. However, it was observed that caterpillars that were exposed to parasitism showed a higher mortality rate, mainly in the pupa stage, suggesting that the parasitism effect may have negatively affected this phase. Tetrastichus howardi was not able to locate and parasite pupae of H. armigera under field conditions in soybean culture.