Prevalence rates of microsporidia in locusts and grasshoppers in South-Western Russia

Locusts and grasshoppers are dangerous polyphagous pests of agricultural crops. In the present paper, results of screening of Acridoidea populations in the South-Western Russia for microsporidia infections including locusts Locusta migratoria, Dociostaurus maroccanus, and Calliptamus italicus and grasshoppers Chorthippus loratus, Oedipoda caerulescens, and Acrida bicolor, are presented. Microsporidia prevalence rates were estimated using light microscopy of fresh smears. Out of 179 specimens of L. migratoria sampled between 2002 and 2019 in Krasnodar Territory, Astrakhan and Rostov Regions, none was infected with microsporidia. Similarly, 95 specimens of D. marrocanus from Krasnodar Territory (2017) and Dagestan Republic (2009) were also negative for microsporidia. Meanwhile, one positive case was detected for C. italicus corresponding to 0.5 % for the total amount of 192 exemplars collected from 2002 to 2019 in Krasnodar Territory, Astrakhan and Rostov Regions. As for grasshoppers, all Ch. loratus samplings in Krasnodar Territory in 2017-2019 were infected at the prevalence rates of 2.2-15 %, though no infection was found in 40 specimens in Crimea in 2019. In 56 individuals of O. caerulescens collected from Rostov Region and Krasnodar Territory, the microsporidia prevalence rate was 1.8 %. Among 96 specimens of A. bicolor, none was infected. In total, the microsporidia prevalence rates were higher in grasshoppers as compared to locusts, the difference being statistically significant at p<0.01

The effect of endophytic colonization of wheat plants by the fungus

The experiments were aimed at evaluation of the effect of feeding with wheat colonized by the fungus Beauveria bassiana on the development of locusts. The seeds were treated with fungal conidia and 90 days after sowing, the plant parts were fed to II instar nymphs of laboratory colonies of migratory and desert locusts within the period of 18 days. The mortality levels between experimental and control (fed with untreated wheat) groups were not significantly different though a tendency of an increase in variants with contaminated fodder was observed. Two weeks after the beginning of the bioassay, insect mortality was 20-30% and 15% in control. As many as 50% of migratory locust and 40% of desert locust cadavers were covered by a fungal mycelium. Sequencing of two diagnostic DNA loci has confirmed attribution of the reisolate to the genotype of the initial Beauveria bassiana strain BBK-1. It can be therefore concluded that the endophyte fungus is capable of causing classical pathogenesis of mycosis in locust nymphs. Moreover, the nymphal development was retarded by feeding with the fungus-colonized plants