DETECTION OF MICROSPORIDIA INFECTING BEET WEBWORM LOXOSTEGE STICTICALIS (PYRALOIDEA: CRAMBIDAE) IN EUROPEAN PART OF RUSSIA IN 2006–2008

J.M Malysh,A.G Kononchuk,A.N Frolov

doi:10.31993/2308-6459-2019-2(100)-45-51

Abstract

The beet webworm Loxostege sticticalis (L.) is a major insect pest that causes serious damage of agricultural crops in Russia, China and adjacent countries. Microsporidia are obligate intracellular parasites that negatively affect population density of many insect hosts including Lepidoptera. In particular, infection with microsporidia is an important mortality factor for L. sticticalis. Special methodology for the identification of microsporidia associated with terrestrial insects is required. In the present paper we report the results of screening beet webworm moths for microsporidia using two techniques, i.e. light microscopy (LM) and PCR. Adult moths were sampled in 2006–2008 in the European part of Russia: Rostov Region, Krasnodar Territory and Republic of Bashkortostan. Microsporidia infections were detected in insects collected from all sampling sites. Examination of smears by LM showed presence of microsporidian spores in 3.4 % of samples (N=98). PCR analysis of the same dataset was positive in 6.7 % of samples, including those containing and not containing spores. The higher infection rate determined by PCR is likely connected with the fact that only mature spores can be unequivocally identified by LM, whereas PCR also allows detection of otherdevelopmental stages of microsporidia. Partial sequencing of an amplicon from Krasnodar Territory showed its close relatedness to Endoreticulatus poecilomonae from Poecilimon thoracicus Fieber (Orthoptera: Tettigoniidae).

Highlights

The beet webworm Loxostege (Pyrausta) sticticalis L. is an important outbreak pest, causing serious damage to the crops such as soybean, sugar beet, alfalfa, sunflower and other crops in Eurasia, including Northern China and steppe zones of European and Asian parts of Russia (Chen Xiao et al, 2008; Frolov et al, 2008)
Recent studies have shown that the insect population density correlated with the prevalence of microsporidian infection in the previous generation, suggesting that microsporidia is an important factor of the regulation of beet webworm populations in nature (Frolov et al, 2008)
We report the results of screening of L. sticticalis adults collected in 2006–2008 at three sample sites located in European part of Russia for microsporidia using light microscopy (LM) and PCR and demonstrate infection with microsporidia belonging to the genus Endoreticulatus

Summary

Introduction

The beet webworm Loxostege (Pyrausta) sticticalis L. is an important outbreak pest, causing serious damage to the crops such as soybean, sugar beet, alfalfa, sunflower and other crops in Eurasia, including Northern China and steppe zones of European and Asian parts of Russia (Chen Xiao et al, 2008; Frolov et al, 2008). Recent studies have shown that the insect population density correlated with the prevalence of microsporidian infection in the previous generation, suggesting that microsporidia is an important factor of the regulation of beet webworm populations in nature (Frolov et al, 2008). Different species of microsporidia are able to infect beet webworm, including Nosema loxostegi (Issi et al, 1980), Tubulinosema sp., Nosema sp., Nosema ceranae (Malysh et al, 2018), Tubulinosema loxostegi (Malysh et al, 2013b) and Vairimorpha thomsoni (Malysh et al, 2013a). The criterion of microsporidian infection rate is included into the specified forecast model of this dangerous agricultural pest (Malysh, 2006), substantiating the need for a reliable, fast and sensitive technique for detection of microsporidian infection. Molecular detection is more sensitive and provides specified data on parasite prevalence, species composition and genetic polymorphism

Methods

Results

Conclusion