Fungal entomopathogens are the most effective biocontrol agents against insect pests in the natural ecosystem. This study was conducted for phenotypic, molecular, and virulence characterization of locally isolated entomopathogenic fungi from soil samples of six localities in Ethiopia. Entomopathogenic fungi were isolated from 120 soil samples with the galleria baiting method. A total of 65 (54.2%) entomopathogenic fungal isolates belongs to Beauveria spp and Metarhizium spp were identified based on cultural and morphological features. All isolates were pre-screened based on germination, vegetative growth rate, and spore production as fungal in-vitro virulence determinates. Isolate AAUKB-11 displayed the peak germination of 99.67% and isolate AAUMFB-77 achieved the highest radial growth rate of 3.43 mm day À1 with the highest sporulation 4.60 Â 10 8 spores/ml. The phylogenetic analysis of ITS-rDNA confirmed that 7 isolates were identified as B. bassiana and 5 isolates were categorized into M. anisopliae. Selected B. bassiana and M. anisopliae strains were evaluated for their pathogenicity efficiency against G. mellonella larvae and caused 86.67%-100% mortality. The mortality rates of G. mellonella larvae peaked at 100% with 4(33.33%) isolates from B. bassiana and 2(16.67%) isolates from M. anisopliae after 10 days of treatments. The high virulent isolate, B. bassiana AAUMB-29 displayed the least LT 50 value of 2.36 days followed by isolate B. bassiana AAUMFB-77 with LT 50 of 2.53 days. Future studies should be needed to focus on the evaluation of high virulent isolates against other potential insect pests to assess their vigorous role as favorable biological control agents.

Objective This study was aimed to assess the enzymatic activity and pathogenicity potential of Beauveria bassiana and Metarhizium anisopliae against whiteflies in Ethiopia. Results The data showed that Beauveria bassiana AAUMB-29, AAUMFB-77, and AAUEB-59 generated the highest chitinase (EI = 3.41), lipase (EI = 4.45), and protease activities (EI = 5.44) respectively. The pathogenicity study of isolates on whitefly nymphs and adults indicated significant variation (P < 0.05) with mortality ranging from 71.67 to 98.33% and 60 to 100% against Bemisia tabaci and Trialeurodes vaporariorum nymphs respectively. The mortality of adults was between 58 and 94.27% against B. tabaci and 59.03 to 95.37% against T.vaporariorum. The result also showed that AAUMB-29, AAUMFB-77, and AAUDM-43 were the most virulent with LC50 values of 2.7 × 104, 5.3 × 104, and 5.4 × 104 conidia/ml against nymphs of B. tabaci, and with LC50 values 6.8 × 104, 8.2 × 104, and 7.2 × 104 conidia/ml against nymphs of T. vaporariorum, respectively. The B. bassiana AAUMB-29, B. bassiana AAUMFB-77, and M. anisopliae AAUDM-43 induced the highest whitefly mortality than other isolates. These isolates can be recommended for further tests under field conditions to fully realize their potential as effective biocontrol agents against whitefly pests in tomato.

Background Bacillus thuringiensis is a Gram-positive, rod-shaped, and spore-forming microbial entomopathogen. The silverleaf whitefly, Bemisia tabaci (Genn.) (Hemiptera: Aleyrodidae), is a worldwide important cryptic species causing serious economic damage to several vegetable crops including tomato. The aim of this study was to characterize and evaluate the bio-insecticidal effects of locally isolated Bacillus thuringiensis (Bt) against Galleria mellonella and Bemisia tabaci. Results Thirty-one isolates of Bt were obtained from 70 soil samples based on cultural characterization coupled with insecticidal crystal protein detection. All of the 31 bacterial isolates were pre-screened for their bio-insecticidal property against the greater wax moth, Galleria mellonella L. larvae. Only 20 (64.5%) isolates were virulent to G. mellonella with a percentage mortality that ranged from 2.50 to 95%. The groEL gene sequences of all 20 entomopathogenic indigenous isolates displayed 99–100% similarity with Bt isolates. Bioassay evaluation of 12 selected isolates against 3rd to 4th nymphal instars of B. tabaci with spore-crystal suspensions of 1 × 109 spores/ml caused 0 to 31.25%, 0 to 57%, and 0 to 82.5% percentage mortality within 48, 96, and 144 h accordingly. Among isolates of Bt, isolate AAUDS-16 had the highest virulence, followed by the isolate AAUES-69D with LC50 values of 9.67 × 106 spores/ml and 1.16 × 107 spores/ml, respectively. The virulent isolates were tested for their growth response to a different temperature range between 15 and 40 °C. All isolates showed a maximum growth rate around 30 °C. Conclusions Bt isolates of AAUES-69D and AAUDS-16 displayed high insecticidal potential against B. tabaci nymphs and G. mellonella larvae, and showed a maximum growth rate in a wide range of temperature. High virulence and temperature-tolerant isolates should be important candidates for diverse insecticidal toxin studies.