Control of Chrysodeixis includens (Lepidoptera: Noctuidae) using Chin-IA (I-A) isolate as integrate component of management in soybean crops

Ana Beatriz Riguetti Zanardo Botelho,Ivana Fernandes Da Silva,Crébio José Ávila

doi:10.1590/1808-1657000712018

Abstract

ABSTRACT Chrysodeixis includens is an important pest of soybean crop who has gained more visibility in the Brazilian Cerrado due to damage caused in this region. Foliar consumption, feeding period and mortality level of soybean loopers in laboratory, as well as their control in the field conditions, were evaluated after application of the ChinNPV virus in soybean plants. In the laboratory, were tested six concentrations of isolate Chin-IA (I-A) (1 × 1011, 2 × 1011, 4 × 1011, 6 × 1011, 8 × 1011 and 10 × 1011 PIB ha-1), one dose of methomyl chemical insecticide (172 g ai ha-1) and distilled water (control). The field experiment was carried out in the 2016/2017 season using the same cultivar and laboratory treatments, except for the lowest virus concentration. The population density of small and large larvae was evaluated before and at 5, 8 and 12 days after application (DAA) of the treatments in soybean plants. All concentrations of the isolate Chin-IA (I-A) have reduced the soybean loopers consumption and their feeding period, showing 100% of mortality after 3 – 4 days without differing from treatment with the chemical insecticide. After eight DAA of virus in the field, the population density of small and large larvae was reduced, providing satisfactory levels of control. These results showed the evident potential of ChinNPV in the reduction of defoliation power and maintenance the soybean loopers population under of control level, and thus may be used as complementary method in the integrated management of this pest in soybean crops.

Highlights

The species Chrysodeixis includens (Walker, 1857) (Lepidoptera: Noctuidae), known as soybean looper, is a polyphagous insect of a large variety leguminous plants (SPECHT et al, 2015)
The larval stage has a behavior of feeding on the leaves of the medial to lower soybean plants canopy, becoming difficult their control by insecticides which need to be applied to the bottom and inside of the plants, resulting in the necessity of higher doses of these products (DEGRANDE; VIVAN, 2008; SOSA-GÓMEZ et al, 2014)
The defoliation occurring in the reproductive period of soybean plants, in which the attack of this pest is most prominent, may reduce the grains production leading to economic damages

Summary

INTRODUCTION

The species Chrysodeixis includens (Walker, 1857) (Lepidoptera: Noctuidae), known as soybean looper, is a polyphagous insect of a large variety leguminous plants (SPECHT et al, 2015). The larval stage has a behavior of feeding on the leaves of the medial to lower soybean plants canopy, becoming difficult their control by insecticides which need to be applied to the bottom and inside of the plants, resulting in the necessity of higher doses of these products (DEGRANDE; VIVAN, 2008; SOSA-GÓMEZ et al, 2014) This species has been shown to be less susceptible to the active ingredients available in the market (ÁVILA et al, 2008; BERNARDI et al, 2012). The Chrysodeixis includens nucleopolyhedrovirus (ChinNPV: Baculoviridae) is an Alphabaculovirus pathogenic and specific to this species, previously known by the genus Pseudoplusia (CRAVEIRO et al, 2016) Due to their high specificity and natural occurrence, these viruses are good candidates for use in management programs because they are harmless to other microorganisms, natural enemies, pollinating bees, vertebrates and plants (MOSCARDI, 1990). The main goal with the present study was to evaluate the effect of concentrations of an isolate [Chin-IA (IA)] from ChinNPV virus on leaf consumption, feeding period and mortality of larval stage of C. includens in the laboratory, and its control under field conditions

MATERIAL AND METHODS

RESULTS AND DISCUSSION

CONCLUSION