Water in maize whorl enhances the control of Spodoptera frugiperda with insecticides

Regina Sonete Stacke,Clérison Régis Perini,Adriano Arrué Melo,Jerson Vanderlei Carús Guedes,Letícia Puntel,Guilherme Padilha,Henrique Pozebon,Adriano Bialozor,Lucas Drebes,Jonas André Arnemann

doi:10.1590/1983-40632020v5059517

Regina Sonete Stacke, Clérison Régis Perini + Show 8 more

Open Access

https://doi.org/10.1590/1983-40632020v5059517

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Abstract

ABSTRACT The fall armyworm Spodoptera frugiperda is among the main insect-pests on maize crops, due to its damaging potential and control issues related to the larval habit of concealing itself within the plant whorl. This study aimed to evaluate the effect of water in the maize whorl, combined with insecticides and spray sets, on the damage caused by S. frugiperda and the grain yield. The experiments were carried out under field conditions, at two cropping seasons, both with Bt-maize hybrids, in a 2 × 2 × 5 + 1 factorial scheme, testing the presence or absence of water inside the plant whorl, two insecticides and five spray sets (combinations of spray volumes, nozzle types, pressures and spraying speed), plus a control without water and insecticide. The presence of water inside the whorl reduced the damage caused by S. frugiperda during the early growth stages, especially in the plants sprayed with the insecticide chlorantraniliprole. The spray sets with 200 L ha1/20.3 psi or 250 L ha1/33.4 psi provided the highest reductions in the percentage of damaged plants and damage scores, regardless of the insecticide. Therefore, the spraying of insecticides, when there is water from irrigation, dew or rainfall inside the maize whorl, improves the control of S. frugiperda in maize crops, especially in Bt-maize.

Highlights

The damage caused by S. frugiperda in maize plants was significantly reduced (p < 0.01) by the presence of water inside the whorls at both experiments, especially at the early growth stages of the plants (Figure 2)
These results indicate that the water inside the maize whorls combined with chlorantraniliprole reduces in more than 10 % the number of plants damaged by S. frugiperda during the early growth stages, regardless of spray set
Insecticide sprays combined with water inside the maize whorls reduce the damages caused by S. frugiperda at early plant growth stages

Summary

Introduction

E. Smith) (Lepidoptera: Noctuidae) can reduce the maize grain yield up to 60 %, according to the sowing date, maize hybrid and plant growth stage at which the damage occurs (Cruz et al 2008). The main control strategy for S. frugiperda is the use of genetically modified maize plants expressing the toxins Cry or Vip (i.e., Bt-maize). Its control has become difficult, due to the increasing occurrence of populations resistant to some Bt toxins (Cruz et al 2013, Farias et al 2014), demanding insecticide sprays in maize plants that should be highly resistant to the S. frugiperda attack (Burtet et al 2017).

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