Efficacy of soil isolates of entomopathogenic fungi against the bulb mite, Rhizoglyphus robini (Acari: Acaridae)

Abstract

The bulb mite, Rhizoglyphus robini, is a serious pest of garlic, onion and other crops. The mite is usually found in association with dangerous fungal pathogens such as Fusarium spp. Control of this pest has relied upon the use of synthetic acaricides but chemical control of the bulb mite is difficult because it is able to develop resistance quickly. Thus, alternative control methods, e.g. biological control, need to be developed and implemented. The aim of this study was to assess efficacy of selected strains of entomopathogenic fungi (EPF) against adult females of R. robini under laboratory conditions. New EPF strains were isolated from soil samples collected in onion and garlic fields in the Czech Republic and Israel using soil elution and cultivation on selective media. Fungal species were determined using macroscopic, microscopic and molecular markers. The efficacy against R. robini females was tested in 17 isolated and 3 reference strains of EPF. Results revealed high variability among species and strains. The highest efficacy against R. robini mites was found in strains of Metarhizium anisopliae isolated from soil samples collected in the Czech Republic which caused mortality up to 99.3%, and a Metarhizium indigoticum strain from Israel causing 98.3% mortality after four days of bioassay. Isaria fumosorosea strains did not caused mortality higher than 40%. The lowest virulence was found in Beauveria spp. strains causing mortality of mites between 5 and 25%. Median lethal time (LT50) and median lethal concentration (LC50) in the three most virulent strains ranged between 2 and 4 days and between 1.01×104 and 2.36×105 spores/ml, respectively. The concentration-response models indicated that the M. indigoticum strain is more lethal than M. anisopliae strains. The present study showed that some strains of entomopathogenic fungi, especially from the genus Metarhizium, could be perspective biocontrol agents against R. robini.

Screening and Identification of Indigenous Entomopathogenic Fungal Isolates from Agricultural Farmland Soils in Nile Delta, Egypt

“…Beauveria spp. are considered the most common cosmopolitan EMPF, parasitizing a wide range of insect species [10,13,43]. Both B. bassiana and M. anisopliae are among the most famous and globally distributed EMPF, revealing significant genetic diversification [44,45].…”

“…In the natural habitat, EMPF are a diverse group of insect-invading fungal pathogens that can effectively infect and regulate numerous insect pest populations [9][10][11]. In this regard, and to benefit from the evolutionary fine-tuned relationship between EMPF and their host insects, it is necessary to obtain and screen potential EMPF isolates and characterize their important properties such as insect host range, environmental persistence, plant growth impact and other important traits.…”

A Review of Prospective Biocontrol Agents and Sustainable Soil Practices for Bulb Mite (Acari: Acaridae) Management

“…[32] Beauveria brongniartii (Sacc.) Petch [32] Cordyceps fumosorosea (Wize) Kepler, B. Shrestha and Spatafora [32] Ophiocordycipitaceae Hirsutella kirchneri (Rostrup) Minter, Brady and Hall [35] Entomopathogenic nematodes…”

“…Kepler, B. Shrestha and Spatafora (formerly Isaria farinosa), and Lecanicillium lecanii (Zimm.) Zare and W. Gams have potential to control some mite species [28,32,34,62].…”

“…To our knowledge, only four studies have tested whether APFs or EPFs are effective in controlling bulb mites under laboratory or greenhouse conditions [32][33][34][35]. Sztejnberg et al [35] reported no pathogenicity of an isolate of Hirsutella kirchneri (Rostrup) Minter, Brady and Hall, obtained from the cereal rust mite, Abacarus hystrix Nalepa (original accession number CMI 257456) against R. robini, despite several procedures attempted for mite infection (spraying, dipping, tipping fungal cultures over hosts).…”