Bacillus Thuringiensis Formulations Research Articles

Biological impact, oxidative stress and adipokinetic hormone activities of Agrotis ipsilon in response to bioinsecticides

The use of biological control products enhances the reduction of harmful pressures on the environment caused by the use of conventional pesticides. Therefore, this study aims to evaluate the toxicity of eight bioinsecticides on the black cutworm Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae) to understand the relationships between insecticide exposure and insect response at the individual and population levels. The bioassay results showed that emamectin benzoate had high toxicity against A. ipsilon second instar larvae with an LC<sub>50</sub> of 0.007 (mg/L). Sublethal concentration (LC<sub>30</sub>) of emamectin benzoate, spinosyn group and Bacillus thuringiensis formulation (Dipel 2X) had significantly prolonged pupal period. In addition, emamectin benzoate significantly decreased the number of eggs laid per female (135.3 ± 6.919) compared with the control treatment. Thus, the formulation of chlorfenapyr showed a 1.26-fold reduction in hatching rate. Meanwhile, the activities of oxidative stress enzymes (catalase, superoxide dismutase, lipid peroxidase, and glutathione reductase) were significantly affected due to exposure to sublethal concentration. Changes in adipokinetic hormone (AKH) transcriptional regulation were detected via SQ-PCR via using cDNA synthesized from mRNA isolated from treated A. ipsilon larvae. The results showed a higher transcription rate of AKH in spinotram-treated larvae with a 1.42-fold increase over untreated larvae. Our results provide useful information for integrated pest management programs for A. ipsilon by using bioinsecticides.

Recycling of spent mushroom substrate biowaste as an Anti-UV agent for Bacillus thuringiensis

It is highly desirable to develop a Bacillus thuringiensis (Bt) formulation with high UV resistibility to increase its application duration in the field. In this work, we studied spent mushroom substrate extract (SMSE) for its anti-UV activity on Bt. The results demonstrated that SMSE could efficiently protect the active components of Bt from UV irradiation. After 96 h of UV exposure, the residual toxicity of Bt fermentation of the SMSE (0.6%, w/v) treatment was 17 times higher than that of the control treatment. SMSE was mainly composed of lignin (77.69%), carbohydrate (7.58%) and protein (4.18%). The anti-UV activity was shown by the lignin and carbohydrate fractions, but not the protein fractions. In addition, it was found that lignin and lignin-carbohydrate complex (LCC) in the SMSE were a type of lignin with low sugar content, low thermal stability, narrow molecular weight distribution and were typical gramineous plant lignin. Lignin and LCC possessed highly UV-screening effects and reactive oxygen species scavenging ability that could improve the UV stability of Bt formulation. Our study provides a green method for the utilization of SMS biowaste and increased the UV stability of Bt formulation.

Evaluation of Bio-Pesticides against the South American Tomato Leaf Miner, Tuta absoluta Meyrick (Lepidoptera: Gelechiidae) in India

Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is one of the most economically important pests of tomato worldwide. Despite its global importance, the management of this oligophagous pest has still been a challenging task, due to its high capability to develop resistance against synthetic insecticides. Given the limited studies on the effectiveness of different bio-pesticides in India, the objective of this research was to determine the pathogenicity of different commercial formulations of Beauveria bassiana, Bacillus thuringiensis, and neem (Azadirachtin), against T. absoluta, under laboratory and field conditions. For the Bacillus thuringiensis formulations, Green Larvicide® and Delfin® recorded an LC50 of 4.10 × 10⁹ CFU/mL and 8.06 × 106 spores/mg, respectively, while for the B. bassiana formulations, Green Beauveria® and BB Power® were 4.473 × 107 spores/mL and 1.367 × 107 CFU/g, respectively. Furthermore, the results showed high susceptibility to both the commercial neem formulations with Ecotin®, recording an LC50 of 91.866 ppm, and Econeem Plus® recording 212.676 ppm. The results from the field conditions at different locations of Andhra Pradesh, India, showed significant differences (p < 0.001) for leaf and fruit infestation among the interaction effect of treatments and locations. Bio-pesticides, especially neem and B. thuringiensis formulations, reduced T. absoluta infestation similarly to the chemical treatment, without affecting the yield. Therefore, bio-pesticides can be considered as safe alternatives to synthetic pesticides, for the management of T. absoluta.

Effectiveness of two biopesticides against the invasive tomato pest Tuta absoluta

AbstractTuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is among the most devastating pests worldwide of solanaceous plants, particularly of tomato (Solanum lycopersicum L.). Since its recent introduction into sub‐Saharan Africa, it has become an additional widespread tomato pest throughout the region. When no control measures are taken, yield losses caused by T. absoluta larvae can reach 100%. Chemical control remains the primary management option despite its many adverse effects and increasing inefficiency due to the species’ endophytic habits and ability to develop insecticide resistance. Safer and more effective alternatives are therefore urgently required. Here, we investigated the effectiveness of two bioinsecticides compared to that of a widely used deltamethrin‐based synthetic insecticide, in preventing damage caused by T. absoluta larvae to tomato leaves and fruits, thereby affecting tomato yield. A field trial was conducted in 2018 and 2019 in northwestern Senegal using a randomized complete block design. Damage caused by T. absoluta affected approximately 65% of total leaf area and 3–24% of the fruits. Damage to the leaves caused by other insect species or other factors was less significant. At the dose applied, the chemical insecticide did not significantly reduce the surface area of leaflets affected by T. absoluta or other causal agents, the number of T. absoluta mines on the leaflets, or the proportion of fruits damaged. In contrast, the azadirachtin and Bacillus thuringiensis (Bt) formulations rapidly and significantly reduced damage to both leaves and fruits. The proportion of fruits damaged was reduced by a factor two and the total tomato yield was improved, particularly when the Bt formulation was used. In addition to their effectiveness in reducing damage caused by T. absoluta larvae to tomato leaves and fruit, and increasing the yield of marketable fruits, the viability of these organic alternatives was shown. The scope of our results is discussed in the context of T. absoluta control, in particular in integrated pest management programmes for tomato crops.

The Effect of Botanical Insecticide Mixed Formulation from Piper aduncum Fruit and Tephrosia vogelli Leaf Against the Diversity of Soil Arthropods in Cabbage Plantation (Brassica oleracea L)

An arthropod is one of the critical animal groups in the agriculture ecosystem. The purpose of this research is to determine the effect of botanical insecticide mixed with formulation from Piper aduncum fruit and Tephrosia vogelii leaf as well as their application intensity against the diversity of soil arthropods. The research was conducted in cabbage plantation regularly applied with pesticide using Randomized Block Design two factorial with 5 treatments and 3 duplications in three regions (Jorong Jambu Kaniki, Batipuh Atas, and Tanah Datar) from March to July 2017. The treatments included control, WP (wettable powder) botanical insecticide formulation, EC (Emulsifiable concentrate) botanical insecticides formulation, BT (Bacillus thuringiensis) formulation, and synthetic insecticide (chlorfenapyr). Soil arthropod samples were taken by pitfall trap at 75 points representing all treatments. The type of formulations and intensity of application affect the number of soil arthropods individuals. There is an interaction between formulations and intensity of application, enhancement on formulations application of WP, and EC tend to increase the number of soil arthropods individual. Otherwise, the use of synthetic insecticide significantly decreases the number of soil arthropod individuals. The application intensity did not affect the type of soil arthropods. Further identification of soil arthropod samples from the experimental field showed the diversity of soil arthropods is categorized as moderate (2,23-2,97), evenness is categorized medium to high (0,25-0,65), index similarity formulations are categorized high (0,923- 1,000), and index similarity intensity application in categorizing medium to high (0,667-1,000). Soil arthropods ware found in cabbage plantations consist of 3 classes: Arachnida (1 Order; 1 Family), Insecta (1 Order; 4 Family), Entoghnata (1 Order; 2 Family). Order Collembola, Family Onychiuridae dominated soil arthropods.

Temporal effect on insecticidal activity of Bacillus thuringiensis Berliner Var. kurstaki, strain ABTS-351, against Corcyra cephalonica

Bacillus thuringiensis (Bt) formulations are the most successful biopesticides now regularly used in many IPM programs against lepidopteran pests. Newer formulations like DiPel contain strain ABTS-351 as active toxin product, which is essentially an isolate of HD-1. Insecticidal activity assay of Dipel DF was performed to characterize the strain for its insecticidal efficacy against Rice moth, Corcyra cephalonica larvae; and the effects of duration of exposure. The obtained mortality curves for the three exposure durations were typically sigmoid as expected. Longer duration of exposure increased the mortality. Lethal concentration values, obtained through Probit analysis for 24, 48 and 72 hrs exposure against log concentration of Bt, yielded LC50 value (with 95% confidence limits) of Bt on C. cephalonica 4th instar larvae as 65.813 (52.946 – 85.689), 36.311 (29.953 – 45.704) and 17.745 (15.350 – 20.742) mg/mL respectively. The insecticidal activity was found to be comparatively much efficient at lower concentrations with longer exposures. This feature is the potential key to a more efficient biocontrol strategy, allowing other compatible biocontrol agents to be combined for a far more effective, or even synergistically, control over pest.

Functional redundancy of structural proteins of the peritrophic membrane in Trichoplusia ni

The peritrophic membrane (or peritrophic matrix) (PM) in insects is formed by binding of PM proteins with multiple chitin binding domains (CBDs) to chitin fibrils. Multi-CBD chitin binding proteins (CBPs) and the insect intestinal mucin (IIM) are major PM structural proteins. To understand the biochemical and physiological role of IIM in structural formation and physiological function of the PM, Trichoplusia ni mutant strains lacking IIM were generated by CRISPR/Cas9 mutagenesis. The mutant T. ni larvae were confirmed to lack IIM, but PM formation was observed as in wild type larvae and lacking IIM in the PM did not result in changes of protease activities in the larval midgut. Larval growth and development of the mutant strains were similar to the wild type strain on artificial diet and cabbage leaves, but had a decreased survival in the 5th instar. The larvae of the mutant strains with the PM formed without IIM did not have a change of susceptibility to the infection of the baculovirus AcMNPV and the Bacillus thuringiensis (Bt) formulation Dipel, to the toxicity of the Bt toxins Cry1Ac and Cry2Ab and the chemical insecticide sodium aluminofluoride. Treatment of the mutant T. ni larvae with Calcofluor reduced the larval susceptibility to the toxicity of Bt Cry1Ac, as similarly observed in the wild type larvae. Overall, in the mutant T. ni larvae, the PM was formed without IIM and the lacking of IIM in the PM did not drastically impact the performance of larvae on diet or cabbage leaves under the laboratory conditions.

Eco-friendly management of tobacco caterpillar with pheromone traps and Bacillus thuringiensis var. kurstaki in Chamba district of Himachal Pradesh, India

During 2018-2019, it was observed that maximum number of adults of S. litura were trapped on 09.07.2018 with 36, 31 and 27 adults trapped per delta trap in Chalunj, Bhanauta and Dulla village, respectively, when the tomato crop was at fruiting stage. But in 2019-2020, maximum number of adults was trapped in the month of June (26th June) in Chalunj (24 adults per trap) and Bhanauta (28 adults per trap) and in July (06th July) in Dulla Village (26 adults per trap) and then there was decrease in the adults trapped per delta traps. The bio-insecticide, Bacillus thuringiensis formulation was effective in controlling the population with efficacy rate of 83.33%.

Single Amino Acid Substitution in Homogentisate Dioxygenase Affects Melanin Production in Bacillus thuringiensis.

Bacillus thuringiensis formulation losing its activity under field conditions due to UV radiation and photoprotection of B. thuringiensis based on melanin has attracted the attention of researchers for many years. Here, a single amino acid substitution (G272E) in homogentisate 1,2-dioxygenase was found to be responsible for pigment overproduction in B. thuringiensis BMB181, a derivative of BMB171. Disrupting the gene encoding homogentisate dioxygenase in BMB171 induced the accumulation of the homogentisic acid and provoked an increased pigment formation. To gain insights into homogentisate 1,2-dioxygenase in B. thuringiensis, we constructed a total of 14 mutations with a single amino acid substitution, and six of the mutant proteins were found to affect the melanin production when substituted by alanine. This study provides a new way to construct pigment-overproducing strains by impairing the homogentisate dioxygenase with a single mutation in B. thuringiensis, and the findings will facilitate a better understanding of this enzyme.

INSECTICIDAL ACTIVITY OF PIPER ADUNCUM FRUIT AND TEPHROSIA VOGELII LEAF MIXED FORMULATIONS AGAINST PLUTELLA XYLOSTELLA (L.) (LEPIDOPTERA: PLUTELLIDAE)

The emulsifiable concentrate (EC) and wettable powder (WP) of Piper aduncum and Tephrosia vogelii mixed formulations were tested for their activities in the laboratory and their effectiveness in the field against cabbage pest Plutella xyostella. Cabbage leaves soaked in six different mixed formulation concentrations were tested against second instar larvae of P. xylostella and observed until the larvae reached fourth instar stage. From the survived larvae, growth and development, antifeedant effects were recorded. Field efficacy test was based on LC95 value of formulations from laboratory test result. The experiment used a randomized block design with 5 treatments and 3 replications to determine the insecticide effectivity against populations of P. xylostella larvae. The results showed that the EC and WP mixed formulations have insecticidal activity against P. xylostella larvae, with LC95 value of 0.35% and 0.37%, respectively. The highest antifeedant effect on EC mixed formulation was 85.01% and WP mixed formulation was 86.23%. Both mixed formulations also slowed the development of larvae when compared with control. Field effication result showed that applications of EC mixed formulation were able to restrain the population of P. xylostella, with effectivity value of 71.06%. Insecticide effectivity value of EC mixed formulation was higher than WP mixed formulation and Bacillus thuringiensis formulation.

Adsorption of Insecticidal Crystal Protein Cry11Aa onto Nano-Mg(OH)2: Effects on Bioactivity and Anti-Ultraviolet Ability.

The traditional Bacillus thuringiensis (Bt) formulations for field applications are not resistant to harsh environmental conditions. Hence, the active ingredients of the Bt bioinsecticides could degrade quickly and has low anti-ultraviolet ability in the field, which significantly limits its practical application. In the present study, we developed an efficient and stable delivery system for Bt Cry11Aa toxins. We coated Cry11Aa proteins with Mg(OH)2 nanoparticles (MHNPs), and then assessed the effects of MHNPs on bioactivity and anti-ultraviolet ability of the Cry11Aa proteins. Our results indicated that MHNPs, like "coating clothes", could effectively protect the Cry protein and enhance the insecticidal bioactivity after UV radiation (the degradation rate was decreased from 64.29% to 16.67%). In addtion, MHNPs could improve the proteolysis of Cry11Aa in the midgut and aggravate the damage of the Cry protein to the gut epithelial cells, leading to increased insecticidal activity against Culex quinquefasciatus. Our results revealed that MHNPs, as an excellent nanocarrier, could substantially improve the insecticidal bioactivity and anti-ultraviolet ability of Cry11Aa.

Impact ofBacillus thuringiensisBerliner var.kurstakiApplication on Population Densities ofPlutella xylostellaL. (Lepidoptera: Plutellidae), and Its Dominant Parasitoid,Cotesia vestalisHaliday (Hymenoptera: Braconidae) and the Implications on Cabbage Yield

Cotesia vestalis Haliday (Hymenoptera: Braconidae) is a solitary koinobiont endoparasitoid that causes high larval mortality of Plutella xylostella L. (Lepidoptera: Plutellidae) on Brassica crops in South Africa. Many farmers use prophylactic and curative microbial insecticides such as Bacillus thuringiensis (Berliner) var. kurstaki (Btk) to minimise damage caused by P. xylostella on their crop. Bacillus thuringiensis formulations are widely adopted based on them not having a direct effect on parasitoids, which then assumes that they complement each other in pest management. We investigated parasitism of P. xylostella by C. vestalis in cabbage fields treated with Btk and assessed the implications on cabbage yield. Populations of P. xylostella and C. vestalis were monitored for 12 weeks in each of the four growing seasons in Btk-treated and control plots at Alice, Eastern Cape, South Africa. Plutella xylostella densities and levels of parasitism were lower in the Btk-treated plots. Consistent with low infestation, damage in Btk-treated cabbage was significantly lower than in the control.

EVALUATION OF BIOPESTICIDES AGAINST THE CAPITULUM BORER HELICOVERPA ARMIGERA ON SUNFLOWER

he different biopesticides were tested against the natural incidence of the capitulum borer Helicoverpa armigera on sunflower crop var. Morden during kharif 2010 in the experimental farm of Marathwada Agricultural University, Oilseeds Research Station at Latur. The experiment was undertaken in a randomized block design (RBD) with seven treatments viz., B. bassiana SC formulation @ 250 mg/L, DOR Bacillus thuringiensis(Bt) formulation @ 2.5 g/L, HaNPV (DOR isolate) @ 2 x 108 POBs/mL Commercial neem formulation 0.5 %, NSKE 5 %,PSE 5%, Profenophos 0.05 % and Untreated Control in three replications with 4.2 x 4.5 m2 plots and row to spacing of 60 x 30 cm. In all two sprayings were undertaken so as to evaluate the effectiveness of the treatment and it was observed that the larval incidence at 1, 3 and 7 days after both spraying was lowest in plots sprayed with Profenophos . However the next best treatments in the order of effectiveness for the control of Helicoverpa were HaNPV @ 2 x 108 POBs/mL, NSKE 5 %, DOR B. bassiana 250 mg, DOR Bt 5 @ 2.5 gm/litre, PSE 5 % and Neem formulation 0.5%. All the biopesticides proved safer to natural enemy but treatment of Profenophos was lethal to them, however, highest yield was recorded with the same (1140 kg/ha) but it is at par with other biopesticides.

Efficacy of olive mill wastewater for protecting Bacillus thuringiensis formulation from UV radiations

The effectiveness of 10 low-cost UV-absorbers in protecting Bacillus thuringiensis subsp. kurstaki BLB1 toxins against inactivation by UV-A and UV-B irradiation was evaluated in this study. Among them, two by-products, molasses and olive mill wastewater (OMW) were selected for further studies. They were tested at different concentrations of 0.05, 0.1, 0.15 and 0.2% using the para-aminobenzoic acid (PABA) as a common UV protectant. Interestingly, addition of PABA and OMW to BLB1 formulations was found to be most effective in protecting BLB1 spores at 90.8 and 76.4% respectively and in preserving delta-endotoxin concentration at a level of 81.7 and 72.2%, respectively when used at a concentration of 0.2%. The lowest preserved spores (46.3%) and delta-endotoxin level (12.4%) was found using molasses. In contrast, spore count and delta-endotoxin concentration were completely reduced after an exposure of unprotected Bt strain BLB1 to UV radiations up to 96h. SDS-PAGE analysis of protected and unprotected samples revealed that delta-endotoxin bands (130, 65–70kDa) were conserved until 96h of UV exposure in presence of PABA or OMW compared with their disappearance in presence of molasses after 72h of exposure and their dramatically decline from 8h of exposure in unprotected mixture. A complete loss of larvicidal toxicity against Ephestia kuehniella was found after 24h of exposure in absence of any UV-absorber. Addition of OMW or PABA offered the highest levels of insecticidal activity with 63.2 and 74.7% of residual toxicity, respectively. Whereas, molasses addition, as UV protectant retained only 26.3% of residual activity after 96h of exposure. Therefore, addition of OMW by-product to Bt formulation may be a suitable alternative to others synthetic chemical compounds. OMW may also provided added value, be environmentally friendly and less hazardous, when used at low concentration.

Antibiotics influence the toxicity of the delta endotoxins of Bacillus thuringiensis towards the cotton bollworm, Helicoverpa armigera

BackgroundThe cotton bollworm, Helicoverpa armigera is one of the most important crop pests worldwide. It has developed high levels of resistance to synthetic insecticides, and hence, Bacillus thuringiensis (Bt) formulations are used as a safer pesticide and the Bt genes have been deployed in transgenic crops for controlling this pest. There is an apprehension that H. armigera might develop resistance to transgenic crops in future. Therefore, we studied the role of gut microbes by eliminating them with antibiotics in H. armigera larvae on the toxicity of Bt toxins against this pest.ResultsCommercial formulation of Bt (Biolep®) and the pure Cry1Ab and Cry1Ac toxin proteins were evaluated at ED50, LC50, and LC90 dosages against the H. armigera larvae with and without antibiotics (which removed the gut microbes). Lowest H. armigera larval mortality due to Bt formulation and the Bt toxins Cry1Ab and Cry1Ac was recorded in insects reared on diets with 250 and 500 μg ml−1 diet of each of the four antibiotics (gentamicin, penicillin, rifampicin, and streptomycin), while the highest larval mortality was recorded in insects reared on diets without the antibiotics. Mortality of H. armigera larvae fed on diets with Bt formulation and the δ-endotoxins Cry1Ab and Cry1Ac was inversely proportional to the concentration of antibiotics in the artificial diet. Nearly 30% reduction in larval mortality was observed in H. armigera larvae from F1 to F3 generation when the larvae were reared on diets without antibiotics (with gut microbes) and fed on 0.15% Bt or 12 μg Cry1Ab or Cry1Ac ml−1 diet, indicating development of resistance to Bt in the presence of gut microflora. However, there were no differences in larval mortality due to Bt, Cry1Ab or Cry1Ac across generations in insects when they were reared on diets with 250 μg of each antibiotic ml−1 diet (without gut microflora).ConclusionsThe results suggested that antibiotics which eliminated gut microflora influenced the toxicity of Bt towards H. armigera, and any variation in diversity and abundance of gut microflora will have a major bearing on development of resistance to Bt toxins applied as foliar sprays or deployed in transgenic crops for pest management.

DIFFERENT BT FORMULATIONS AGAINST POD BORER COMPLEX IN PIGEONPEAECOSYSTEM

ABSTRACT An experiment was conducted to evaluate different Bacillus thuringiensis formulations for the management of podborers on pigeonpea for two years during 2010-11 and 2011-12 at Zonal Research Station, University of Agricultural Sciences, GKVK, Bangalore. Three formulations of Bt viz., Dipel, Halt and DOR were tested at 1.0 and 1.5 kg per ha and indoxacarb at 60 g a. i per ha was used as check. The results revealed that the lowest mean pod damage by Helicoverpa was recorded in indoxacarb with 19.94 per cent. Among Bt formulations, DOR Bt formulation at 1.5 kg per ha proved better by recording 28.89 per cent. The damage by podfly andfield infestation by bruchid was also of the same trend. Total pod damage was also in indoxacarb with 40.61followed by DOR Bt formulation at 1.5 kg per with 54.64 percent. Highest yield was recorded in indoxacarbtreatment with 1087 kg per ha followed by DOR Bt formulation with 895 kg per ha. The lowest yield was observed in untreated control with 599 kg per ha which was inferior to all other treatments.

Further research on the biological function of inclusion bodies ofAnomala cupreaentomopoxvirus, with special reference to the effect on the insecticidal activity of aBacillus thuringiensisformulation

Entomopoxviruses (EVs) form two types of inclusion body: spheroids, which contain virions, and spindles, which do not. The authors tested whether the spindles from a coleopteran EV, Anomala cuprea EV (ACEV), enhanced the insecticidal activity of a commercial Bacillus thuringiensis (Bt) formulation and the susceptibility of scarabaeid pest species in Japan to the virus's spheroids, to assess whether ACEV inclusion bodies are potential biological control agents for pest insects. Peroral inoculation with both ACEV spindles and the Bt toxin only or the complete Bt formulation shortened the survival and increased the mortality of treated insects compared with those of insects inoculated with Bt without the spindles (8-38 h of decrease in LT50 values among assays). ACEV showed high infectivity to a major scarabaeid pest species in Japanese sugar cane fields. The results suggest that spindles or the constituent protein fusolin can be used as a coagent with Bt formulations, and that fusolin coexpression with a Bt toxin in crops might improve the insecticidal efficacy. In addition, the spheroids are potential biocontrol agents for some scarabaeid pests that are not easy to control because of their underground habitation.

Inhibition effect of propionates on the insecticidal activity of BT (Bacillus thuringiensis) formulations

Inhibition effect of propionates on the insecticidal activity of BT (Bacillus thuringiensis) formulations

Biochemical effects of three commercial formulations of Bacillus thuringiensis (Agerin, Dipel 2X and Dipel DF) on Spodoptera littoralis larvae

Effectiveness of commercialformulations of Bacillus thuringiensis var Kurstaki Agerin, Dipel 2X and Dipel on total protein and lipid contents were studied. Activities of detoxification and metabolic enzymes were also measured in treated and control larvae of cotton leafworm Spodoptera littoralis. Collected samples from treated larvae at intervals of 48 and 120 hrs post treatment were analyzed to assess the total protein and lipid contents as well as the enzymes activities. Significant reductions were observed in total protein content at 120 hrs larvae in all treatments compared with control. In all larvae treated with Agerin and Dipel DF the lipid content was significantly elevated after 48 and 120 hrs of treatment while Dipel 2X showed no significant difference in lipid content. However, fluctuated changes in the enzymes activity of treated larvae were found. We conclude that there are differences in biochemical effects between various commercial formulations of Bacillus thuringiensis kurstaki. In most cases Agerin was found more effective on S. littoralis than others.

Characterization of melanin produced by a wild-type strain of Bacillus cereus

Bacillus cereus 58 (Bc58) is a UV-resistant wild type strain that has an ability to produce a sorrel pigment induced by L-tyrosine. The Fourier-transform infrared (FT-IR) spectra and chemical tests of its pigment are similar to that of the standard melanin (Sigma). A bioassay shows that the LC50 of a Bacillus thuringiensis (Bt) formulation added with the melanin of Bc58 and exposed to UV for 5 h is 16.1 μg/ml, which is similar to that of the Bt formulation without UV treatment, however, it is almost double that of the Bt formulation exposed to UV without the melanin of Bc58. The result of SDS-PAGE indicates that the melanin of Bc58 can protect the insecticidal crystal proteins from degradation. This suggests that it is an excellent UV protective agent for the insecticidal crystal proteins of the Bt formulation.