Parasitism performance and fitness of Cotesia vestalis (Hymenoptera: Braconidae) infected with Nosema sp. (Microsporidia: Nosematidae): implications in integrated pest management strategy.

Nadia Kermani,Zainal-Abidin Abu Hassan,Mansour Attia,Noor Farehan Ismail,Idris Abd Ghani,Amalina Suhaimi,Ismail Abuzid

doi:10.1371/journal.pone.0100671

Nadia Kermani, Zainal-Abidin Abu Hassan + Show 5 more

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https://doi.org/10.1371/journal.pone.0100671

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Abstract

The diamondback moth (DBM) Plutella xylostella (L.) has traditionally been managed using synthetic insecticides. However, the increasing resistance of DBM to insecticides offers an impetus to practice integrated pest management (IPM) strategies by exploiting its natural enemies such as pathogens, parasitoids, and predators. Nevertheless, the interactions between pathogens and parasitoids and/or predators might affect the effectiveness of the parasitoids in regulating the host population. Thus, the parasitism rate of Nosema-infected DBM by Cotesia vestalis (Haliday) (Hym., Braconidae) can be negatively influenced by such interactions. In this study, we investigated the effects of Nosema infection in DBM on the parasitism performance of C. vestalis. The results of no-choice test showed that C. vestalis had a higher parasitism rate on non-infected host larvae than on Nosema-treated host larvae. The C. vestalis individuals that emerged from Nosema-infected DBM (F1) and their progeny (F2) had smaller pupae, a decreased rate of emergence, lowered fecundity, and a prolonged development period compared to those of the control group. DBM infection by Nosema sp. also negatively affected the morphometrics of C. vestalis. The eggs of female C. vestalis that developed in Nosema-infected DBM were larger than those of females that developed in non-infected DBM. These detrimental effects on the F1 and F2 generations of C. vestalis might severely impact the effectiveness of combining pathogens and parasitoids as parts of an IPM strategy for DBM control.

Highlights

The diamondback moth (DBM) Plutella xylostella (L.) (Lep., Plutellidae) is a cosmopolitan pest that causes serious damage to a wide variety of cruciferous and other crops
In this study we investigated the effects of Nosema-infected DBM on: (1) the parasitism rate by C. vestalis and its F2 progeny and (2) the body size, fecundity, and morphometric characteristics of C. vestalis that developed on Nosema-infected hosts
Fewer C. vestalis pupae (F = 43.5; df = 4, 20; P,0.05) and adults (F = 60.7; df = 4, 20; P,0.05) developed from the host larvae fed each concentration of Nosema sp. spores than those developed from uninfected DBM larvae

Summary

Introduction

The diamondback moth (DBM) Plutella xylostella (L.) (Lep., Plutellidae) is a cosmopolitan pest that causes serious damage to a wide variety of cruciferous and other crops. This pest has been routinely controlled using chemical insecticides; the excessive use of these products has caused several concerns related to the development of resistance [1,2,3,4], the presence of pesticide residues in the environment and human food [1], and the impact of pesticide applications on populations of non-target organisms [5,6]. Paranosema locustae (Nosema) was developed as a longterm agent for grasshopper control in the USA [9] and in different areas of Argentina [10,11]

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