Susceptibility of onion armyworm, spodoptera exigua (HÜBNER) (lepidoptera: Noctuidae), larvae to spodoptera exigua multiple nucleopolyhedrovirus (seMNPV)

Abstract

© 2019, International Society for Southeast Asian Agricultural Sciences. All rights reserved. Bioassays were carried out to determine the effect of Spodoptera exigua multiple nucleopolyhedrovirus (SeMNPV) to the different larval instars of Spodoptera exigua from May to September 2018 at the National Crop Protection Center, University of the Philippines Los Baños. Fresh castor leaves were treated with crude SeMNPV concentrations of 103-108 polyhedral inclusion body (PIB)/ml and were fed to five larval instars. Larval mortality increased with increasing crude SeMNPV concentrations. The 1st instar larvae were the most susceptible with >80% mortality, while 10-93% mortality was recorded in older larvae. The virus caused disintegration of larval body and distortion in pupae. Based on probit analysis, lethal dose (LD)50 ranged from 7.05 x 105 to 1.71 x 109 PIB/ml. Higher SeMNPV doses are required to cause lethal infection in older larvae population. The LD50 and LD95 from 1st to 5th larval instar increased by 94 and 33,333 times, respectively. The virus significantly affected the growth and development of the larvae by prolonging the larval period and decreasing pupation rate (0-60%) and adult emergence (0-40%). Less than 50% of the treated 4th and 5th larval instars pupated and emerged into adults. This research suggests that SeMNPV is infective to various larval instars of S. exigua resulting in high mortality and reduced growth and development.

Source or Periodical Title

Journal of the International Society for Southeast Asian Agricultural Sciences

ISSN

8593132

Page

23-30

Document Type

Article

Subject

Biological control, Onion armyworm, Polyhedral inclusion bodies, SeMNPV, Spodoptera exigua

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