Efficacy of an Omani strain ofCordyceps javanicaand its culture filtrate against whitefly (Bemisia tabaci) under laboratory conditions

Abstract

In this study, an entomopathogenic fungus was isolated from whitefly (Bemisia tabaci) cadaver samples collected from eggplant fields in Barka, Oman. The fungus was identified as Cordyceps javanica based on sequence analysis of ribosomal DNA internal transcribed spacer (ITS) regions. Under in vitro conditions, the fungus was able to grow between 20°C and 30°C, with a maximum growth at 30°C. No growth occurred at 35°C. Studies on the efficacy of different concentrations of conidia of C. javanica against whitefly nymphs revealed that the mortality rate increased with the increase in concentrations of inoculum. About 95.6 ± 2.1% corrected mortality was recorded at a concentration of 10 7 conidia ml −1 after 7 days of treatment. The culture filtrate of C. javanica exhibited toxicity against whitefly nymphs and recorded 61.3 ± 9.5% corrected mortality after 48 h of treatment. There was no significant difference between the mortality caused by conidial suspension and culture filtrate. Gas chromatography-mass spectrometry (GC-MS) analysis revealed the presence of 17 compounds in the culture filtrate of C. javanica. Lauric acid was present in the largest amount (28.7%) and the long chain (C22-25) hydrocarbons contributed 38.3%. This is the first report on the isolation and characterization of C. javanica from B. tabaci from Oman.

Identification and virulence of entomopathogenic fungi, Isaria javanica and Purpureocillium lilacinum isolated from the whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) in Malaysia

“…The isolation, identification, and virulence test of the fungal isolates are the important steps in developing EPF as BCA (Dayanti et al 2018). Shah et al (2020) had been previously isolated strains of I. javanica from the cadaver of B. tabaci sampled from the field of eggplant in Oman. Moreover, I. javanica had been isolated from several agricultural insect pests such as Asian citrus psyllid, Diaphorina citri Kuwayama, (Ou et al 2019); Sunn pests (Eurygaster spp.…”

“…Third and fourth instars were removed from the leaves by needles, and the number of the second instar was counted and adjusted to 20-25 before dipping into different concentrations. The excised leaves were air-dried and placed on the abaxial surface up in a dishes (90 mm diameter) line with a skinny layer of 1.5% agarose gel (Shah et al 2020). The control excised leaves were dipped in 0.01% Tween 80, and all the treatments were incubated at 25 ± 2 °C.…”

“…Adults and nymphs of B. tabaci cause damage to the plant directly during feeding and oviposition and indirectly through the transmission of plant. Moreover, sooty mold colonizes on the surface of plants due to honeydew secreted by B. tabaci affecting photosynthetic activity in plants, resulting in a considerable decrease in agricultural product quality (Shah et al 2020). Plant viruses transmitted by B. tabaci, such as begomoviruses are estimated to cause yield losses ranging from 20 to 100% and losses worth millions of dollars (Gangwar and Charu 2018).…”