Abstract
Helicoverpa armigera (Hübner) is a polyphagous insect of difficult control and maize is an important host crop of this insect. Entomopathogenic nematodes (EPNs) are control agents of soil pests. This study aimed to verify the action of EPNs for the control of H. armigera pupae. Laboratory and greenhouse bioassays were conducted to select the concentration of nematode application and subsequently field test were conducted. It was obtained that Heterorhabditis amazonensis MC01 at the concentration of 400 infective juveniles (IJs) ·pupa-1 caused the highest mortality in a lower concentration, whereas for H. amazonensis JPM4, concentrations of both 200 and 400 IJs ·pupa-1 were similar causing pupae mortality. In the greenhouse, H. amazonensis MC01 caused mortality reached values of 80% after 10 days, at concentrations of 600 and 800 IJs ·pupa-1. The highest mortality caused by Steinernema carpocapsae was observed at eight days after the juvenile application, at a concentration of 600 IJs ·pupa-1, also reaching 80% mortality. In the field test, both forms of application were considered appropriate for H. amazonensis MC01, causing mortality rates of up to 80%.
Highlights
Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) is a cosmopolitan pest that feeds on at least 170 species of plants, including important crops, since cotton, soybean and beans (JHA et al, 2012)
It was obtained that Heterorhabditis amazonensis MC01 at the concentration of 400 infective juveniles (IJs) ·pupa-1 caused the highest mortality in a lower concentration, whereas for H. amazonensis JPM4, concentrations of both 200 and 400 IJs ·pupa-1 were similar causing pupae mortality
Regarding concentration of IJs suspension to control H. armigera pupae, it was verified that mortality showed sigmoidal behavior, with a positive correlation between concentration mortality for H. amazonensis MC01
Summary
Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) is a cosmopolitan pest that feeds on at least 170 species of plants, including important crops, since cotton, soybean and beans (JHA et al, 2012). The caterpillars prefer to feed on the shoots and reproductive organs of plants, resulting in high annual costs spent on control, besides production losses that reach US$ 5 billion (LAMMERS; MACLEOD, 2007; CZEPAK et al, 2013). Other characteristics of this species are its high mobility, fecundity and ability to survive. These characteristics favored the establishment of this insect in Brazil, where it has reached the status of pest and has become a major phytosanitary problem in several maize-producing regions of the country (ÁVILA et al, 2013).
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