Isolation, characterization, and bio-insecticidal efficiency of Ethiopian isolates of Bacillus thuringiensis against Galleria mellonella L. (Lepidoptera: Pyralidae) and tomato whitefly, Bemisia tabaci (Genn.) (Hemiptera: Aleyrodidae)

Abstract

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.

Greater wax moth control in apiaries can be improved by combining Bacillus thuringiensis and entrapments

“…The technique entails the creation of a modified synthetic diet and a survival environment that are conducive to the growth and development of the larvae in vitro and is based on their nutritional needs and rearing conditions. Compared to the previous bioassay for multiple GWM larvae exposed simultaneously to Bt with a comb or common diet as the carrier 43 , 46 , 47 , the modified synthetic diet and the rearing method in vitro are more precise in measuring the toxicity of Bt, as they eliminate various confounding factors, such as interindividual competition and escape behaviour, and the survival of the negative control group reached up to 95%; however, the obtained data could provide more effective and targeted measures to manage wax moth infestations (Fig. 1 ; Table 1 ; Supplementary Fig.…”

The Endophytism of Bacillus thuringiensis in Cotton Plants at Acquisition and Oviposition by Bemisia tabaci

“…In that research, the strain GP139 of Bt was used to show the toxic activity against B. tabaci [37], in addition the high virulence of this Bt strain observed in bioassays performed with Myzus persicae Sulzer (Hemiptera: Aphididae) [30]. Bacillus thuringiensis isolates were selected for their high insecticidal potential against nymph's whitefly under in vitro conditions [38]. Native isolates of Bt from soil environments caused up 50 to 70% mortality of B. tabaci nymphs [20] and mortality with superior percentage of 90% [22].…”

“…In these reports, the studies evaluated strains, toxins and derived products of Bt against B. tabaci by immersion or spraying of the bacterial suspension in surface of leaves and insect bodies [8,20,22,30,37,38]. But the action of Bt sap has not been reported to this pest.…”

Integrated Potential of Microbial, Botanical, and Chemical Pesticides for the Control of Viral Disease Vector Whiteflies (Hemiptera: Aleyrodidae) on Tomato under Greenhouse and Field Perspectives

“…Sources of Microbial Bioinsecticides. Entomopathogenic microbial isolates of AAUMB-29 (B. bassiana), AAUMFB-77(B. bassiana), AAUDM-43 (M. anisopliae) [40], and AAUES-69D (B. thuringiensis) [41] were isolated from soil and identified using molecular identification methods (Table 1).…”