Persistence of insecticidal activity of novel bio-encapsulated formulations of Bacillus thuringiensis var. kurstaki against Choristoneura rosaceana [Lepidoptera: Tortricidae] (original) (raw)
Related papers
World Journal of Microbiology and Biotechnology, 2020
Bacillus thuringiensis (Bt) and entomopathogenic fungi (EPF) are in use for management of insect pests. Continuous use of Bt can lead to problem of resistance development in insect pests. Hence use of combination formulations (CF) of microbials with diverse modes of action has been attempted to slow down the process of resistance development. Suspension concentrate (SC) formulations of a local strain of Bt var. kurstaki DOR Bt-127 were developed singly and in combination with conidia of the EPF Nomuraea rileyi (Nr) and Beauveria bassiana (Bb). Electron microscopy of Bt + Bb CF treated larvae of Helicoverpa armigera revealed simultaneous infection by both microbials indicating their compatibility. Endotoxin contents in Bt-SC, Bt + Bb and Bt + Nr CFs were 5.0, 4.7 and 4.7%, respectively. These formulations were effective against larvae of Spodoptera litura, H. armigera and Achaea janata coupled with a lowering of the effective requirement of Bt and EPF. In multi-location field trials, Bt-SC and Bt + Nr CF were highly effective against S. litura and A. janata on castor as well as H. armigera and Thysanoplusia orichalcea on sunflower. However, Bt + Bb CF was highly effective only on sunflower against H. armigera and T. orichalcea. All formulations had 24 months shelf-life at room temperature. DOR Bt-127 based SC formulations developed singly and in combination with Nr and Bb were effective against major lepidopteran pests of castor and sunflower and did not lose viability under storage at room temperature. The CFs of Bt with EPF could prove promising for mitigating resistance development to Bt.
2018
The entomopathogenic bacterium Bacillus thuringiensis (Bt) has been used in crop protection for the last 70 years; however, many environmental conditions affect its activity. The present study was directed to evaluate the influence of certain environmental conditions on stability and activity of Bt samples of the two commercial formulations (Dipel 2 × 6. 4% WP and Protecto 9.4% WP), when stored under accelerated hot storage, shelf, and outdoor storage. Photo degradation of the two formulations was studied in aqueous solution. The results revealed that the loss percentage of Protecto formulation was above the permissible limits of WHO specifications after 2 years of storage at ambient conditions and the thermal stability of the Bt was affected negatively depending on the storage periods. In accordance with this trend, the bioassay tests versus neonate and second instar larvae of the cotton leaf worm, Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae), showed a decrease in toxicity of the formulations to (60%) after storage at 35 ± 2°C for 12 weeks and about (70%) after storage under sunlight for 2 days. Photolysis of aqueous solutions reduced the half-life of formulations by about 1-2 days. The stability of Bt should be evaluated prior to submission for registration as these products have showed less stability under storage at ambient conditions. The stakeholders and decision-makers can utilize these results and examine such products case by case.
Pakistan Journal of Zoology, 2020
to check the efficacy of commercial biopesticides under controlled environmental conditions. Bio pesticides are important alternates for chemical control of economically damaging insect pests like leaf worm, Spodoptera litura Fabricius. In this study, two commercial products including Dipel with Bt sub speciess kurstaki and Turex with Bt sub speciess kurstaki and aizawai were tested against three early larval instars of S. litura under laboratory conditions using leaf dip method. Mortality was recorded after three and seven days of exposure. The results indicated that larval mortality increased with time and Turex (Bt sub speciess kurstaki and aizawai) after 3 days of exposure caused significantly higher mortality i.e 46.43, 43.45 and 38.69 % as compared to Dipel (Bt sub speciess kurstaki) that caused 19.05, 6.55 and 4.76 % mortality for 1 st , 2 nd and 3 rd instar, respectively. The data for 7 th day also showed significantly higher mortality as 64.29, 60.71 and 45.24 % by Turex (Bt sub speciess kurstaki and aizawai) in comparison with 55.95, 57.74 and 42.86 % mortality by Dipel (Bt sub species kurstaki) for 1 st , 2 nd and 3 rd instar, respectively. Susceptibility to both bio pesticides increased with increase in their concentration and decreased with increase in larval instar. Similarly LC 50 values suggested Turex (Bt sub species kurstaki and aizawai) to be more toxic with less LC 50 values as compared to Dipel (Bt sub species kurstaki). These results indicated that these bio pesticides if used at early insect stage can help to control this pest.
Journal of Economic Entomology, 1998
The toxicity of 6 strains of Bacillus thuringiensis representing 4 serovars, aiwwai, galleriae, kurstaki, and kumamotoensis, were evaluated in laboratory and field studies for activity against 3 lepidopteran crop pests, Heliothis virescens (F.), Spodoptera eXigua (Hubner), and Trichoplusia ni (Hubner). Results oflaboratory tests showed that some B. thuringiensis strains isolated from Mexico (GM-7 and GM-10), were sufficiently toxic to warrant further investigation as potential bioinsecticides for lepidopteran control. Nixtamalized corn flour was used to create a B. thuringiensis granule formulation that remained toxic for at least 2 yr. Field tests were conducted in 1994 and 1995 on corn plots in a semiarid region in central Mexico. Granular formulations were made with 2% (wt:wt) or 4% (wt:wt) of a spore-crystal B. thuringiensis concentrate and tested with carbaryl and Dipel 2X. In 1994, the corn yields obtained from plots treated with 2 strains from the Howard Dulmage collection (HD-187 and HD-193-kurstaki and gallmae, respectively) and 1 Mexican strain (GM-10, aizawai) at 2% were significantly higher than from plots treated with Dipel 2X or the untreated control. Formulations of 4% containing strains GM-7, GM-10, HD-187, HD-193, and HD-263 provided better insect control than formulations made with C-4. These tests indicated that B. thuringiensis survived in the nixtamalized flour matrix complex and was effective in causing pest reduction. In the 1995 field test, the 3 most toxic strains were evaluated individually or by mixing 2 in the same granular formulation at a total dose of 3%. The highest yields of corn were obtained from plots treated with strain HD-263 (kurstaki), which had originally shown the highest efficacy in laboratory bioassays, and with strain GM-10 (aizawai), formulated 2 yr earlier. These data suggest that the product can be produced and retain shelf life suitable for commercialization.
Journal of Economic Entomology, 2000
Bacillus thuringiensis Berliner is a highly efficacious bioinsecticide used to control lepidopteran pests in the field. Unfortunately, it has limited residual activity on plants because sunlight inactivates spores and crystals and they can be washed off by rain. To minimize loss of activity, formulations must contain lTV protectants, stickers, or both. We tested =80 formulations and determined optimal combinations of ingredients and spray drying conditions for improving B. thuringiensis residual activity after simulated rain and simulated sunlight. B. thuringiensis stability, after simulated sunlight (xenon Iight/8 h) and rain (5 em/50 min), was improved using formulations based on lignin, corn flours, or both, with up to 20% of the active ingredient, when compared with technical powder or Dipel 2X in laboratory assays. Two formulations, made with corn flours or lignin + pregelatinized corn flour (PCF), killed 51.6 and 75.3% of Ostrinia nubilalis (Hubner) neonates after rain, respectively, versus 27% for technical powder. When the insecticidal activity was tested after simulated sunlight, corn flour-based formulations killed 78.5% of test larvae, and the lignin + PCF formulation killed 70.4%, in contrast to technical powder which caused an average of 29% mortality. Formulations made with Dipel 2X rather than technical powder, caused 62.5% mortality (corn flour-based formulations), and 72.3% mortality (lignin + PCF), versus 53.4% for Dipel 2x after rain. When tested after simulated sunlight, formulations killed 95% of the larvae (average of both formulations) versus 82% for Dipel 2x. In a field test, formulations were applied to cabbage and insecticidal activity was determined against Trichoplusia ni (Hubner) neonates exposed to treated leaves. Insecticidal activity of the corn flour-based formulations was comparable to Dipel 2x for 4 d after treatment, but was signiflcantly better than Dipel 2x 7 d after application. A lignin and PCF-based formulation showed signiflcantly higher residual activity than Dipel 2X, 4 and 7 d after application.
Egyptian Journal of Biological Pest Control
The present study focuses on the evaluation of the potential of a Tunisian Bacillus thuringiensis (Bt) isolate named Hr1, isolated from dead and diseased pod borer, Helicoverpa armigera Hübner (Lepidoptera: Noctuidae) larvae under laboratory and field semi-controlled conditions. The bacterial strain Hr1 showed an insecticidal activity against the pest's neonates in comparison to the spinosad-based insecticide (Tracer 240 SC®) during bioassays under laboratory conditions. A carboxymethyl cellulose-talc (CMC-talc)-based formulation of the Bt isolate was prepared to evaluate the potential of the bacterium on tomato plants infested with H. armigera under semi-controlled field conditions with and without rain simulation. The results showed the efficacy of the formulation than the spinosad-based insecticide and the treatment with unformulated bacterium. The results also showed the persistence of Bt isolate activity even after rain-wash than the treatment with unformulated bacterium.
Journal of Economic Entomology, 2000
Bacillus thuringiensis Berliner is a highly efficacious bioinsecticide used to control lepidopteran pests in the field. Unfortunately, it has limited residual activity on plants because sunlight inactivates spores and crystals and they can be washed off by rain. To minimize loss of activity, formulations must contain lTV protectants, stickers, or both. We tested =80 formulations and determined optimal combinations of ingredients and spray drying conditions for improving B. thuringiensis residual activity after simulated rain and simulated sunlight. B. thuringiensis stability, after simulated sunlight (xenon Iight/8 h) and rain (5 em/50 min), was improved using formulations based on lignin, corn flours, or both, with up to 20% of the active ingredient, when compared with technical powder or Dipel 2X in laboratory assays. Two formulations, made with corn flours or lignin + pregelatinized corn flour (PCF), killed 51.6 and 75.3% of Ostrinia nubilalis (Hubner) neonates after rain, respectively, versus 27% for technical powder. When the insecticidal activity was tested after simulated sunlight, corn flour-based formulations killed 78.5% of test larvae, and the lignin + PCF formulation killed 70.4%, in contrast to technical powder which caused an average of 29% mortality. Formulations made with Dipel 2X rather than technical powder, caused 62.5% mortality (corn flour-based formulations), and 72.3% mortality (lignin + PCF), versus 53.4% for Dipel 2x after rain. When tested after simulated sunlight, formulations killed 95% of the larvae (average of both formulations) versus 82% for Dipel 2x. In a field test, formulations were applied to cabbage and insecticidal activity was determined against Trichoplusia ni (Hubner) neonates exposed to treated leaves. Insecticidal activity of the corn flour-based formulations was comparable to Dipel 2x for 4 d after treatment, but was signiflcantly better than Dipel 2x 7 d after application. A lignin and PCF-based formulation showed signiflcantly higher residual activity than Dipel 2X, 4 and 7 d after application.
Activity ofBacillus thuringiensis- and Baculovirus-Based Formulations toSpodopteraSpecies
Southwestern Entomologist, 2017
Several formulations based on a palatable carrier suspension: Bacillus thuringiensis Berliner HD-133 strain; beet armyworm, Spodoptera exigua (Hübner), multiple nucleopolyhedrovirus (SeMNPV); and fall armyworm, Spodoptera frugiperda (Hübner), multiple nucleopolyhedrovirus (SfMNPV); alone or combined were developed and evaluated for activity against Spodoptera exigua and S. frugiperda larvae. Bioassays to determine the most active agents for each insect species were three treatments for spore-crystal complex, three for occlusion bodies for each of the two viruses, and four treatments combining all of them in different concentrations. Feeding preference was bioassayed with natural ingredients to obtain a palatable carrier for the active agents. Carrier suspensions were prepared with dehydrated soy leaves as a feeding stimulant for both pests for formulation preparation. Formulations containing the lower and medium concentrations of HD-133 strain and SeMNVP (SeB1V1 and SeB2V2) showed synergism against S. exigua, whereas formulations containing medium and high concentrations (SfB2V2 and SfB3V3, respectively) offered additive interaction against S. frugiperda.
Efficacy of Bacillus thuringiensis Against Phyllocnistis citrella (Lepidoptera: Phyllocnistidae)
Journal of Economic Entomology, 2005
The purpose of this work was to analyze the efÞcacy of Bacillus thuringiensis Berliner on the control of Phyllocnistis citrella Stainton (Lepidoptera: Phyllocnistidae) in laboratory and Þeld trials. In the laboratory, four B. thuringiensis were used: Dipel (commercial formulation) tested at the concentrations of 25 ϫ 10 6 and 25 ϫ 10 8 spores/ml and the isolates K, 6, and 15 (collections of the University of Azores) at the concentration of 25 ϫ 10 6 spores/ml. A surfactant solution of nonoxinol also was tested with or without the different suspensions of B. thuringiensis. Leaves of Citrus sinensis (L.) Osbeck with second or third instars of leafminer larvae were used in all tests. Bacterial suspensions were applied topically on the surface of intact leaf mines or by injection inside the mine, near the head of the leafminer. When injecting both concentrations of Dipel into the mines, mortality of the leafminers increased compared with the topical application, although no signiÞcant differences were observed. The addition of the nonoxinol to the Dipel suspension, applied topically, increased the effect of B. thuringiensis, but differences were not signiÞcant. The mortality of the leafminers treated only with the nonoxinol solution increased signiÞcantly 48 h after treatment, compared with the control group, suggesting an insecticidal effect of this surfactant when used at a concentration of 0.01%. All the tested B. thuringiensis were equally active against the leafminer, either when applied topically or by mine injection. Field trials showed a signiÞcant difference between larval mortality of the control group and the results observed at the trees treated with B. thuringiensis 48 h after treatments.