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PubMed2026

Characterization and genomic analysis of Bacillus halotolerans G3-2: a potential biocontrol agent against apple Alternaria leaf blotch disease.

BACKGROUND: Apple Alternaria leaf blotch (ALB) is a devastating disease threatening the apple industry worldwide. Biocontrol offers an effective and environmentally friendly alternative for disease management. RESULTS: Bacillus strain G3-2 exhibits strong antagonistic activity against Alternaria alternata (a major causal pathogen of ALB). In dual-culture assays, G3-2 inhibited A. alternata by 88.39%; in detached-leaf inoculation assays, it reduced the lesion area by >88%. 16S rRNA sequencing and phylogenetic analysis identified this strain as Bacillus halotolerans. Oxford Nanopore Technology (ONT) sequencing generated a 4.18-Mb complete genome (43.8% G + C) containing 4149 protein-coding genes, 30 rRNAs and 86 tRNAs. CAZy annotation identified 182 genes encoding carbohydrate-active enzymes (CAZymes), including glycoside hydrolases, glycosyltransferase, and carbohydrate esterases, suggesting potential for glycosylated secondary metabolite production. AntiSMASH analysis detected nine biosynthetic gene clusters, including those for surfactin, fengycin, bacillaene and laterocidine. Plate assays confirmed that G3-2 has the ability to produce protease, cellulase and siderophore. Moreover, it exhibits ~70% inhibition against several other phytopathogenic fungi. CONCLUSIONS: These findings demonstrate that G3-2 suppresses A. alternata through antibiosis (lipopeptides and polyketides), nutrient competition (siderophores) and cell-wall degradation (proteases and cellulases). Moreover, our study revealed that it has great potential to be used as a broad-spectrum, environmentally friendly biocontrol agent. © 2026 Society of Chemical Industry.

Alternaria↗
PubMed2005

Persistence and coexistence of engineered baculoviruses.

Baculoviruses, and in particular, the nucleopolyhedroviruses infect a wide range of arthropod hosts and have the potential to be used as biopesticides. However, one of the major drawbacks with these pathogens as biocontrol agents is that they have a slow response time. Alterations to the speed of kill and pathogen life history characteristics can influence the competitive outcome and persistence between wildtype and modified strains. Here, we explore, theoretically, how life-history modifications of pathogens can affect the epidemiology and ecology of strain coexistence. In particular, we show how under simple mass action disease transmission, life-history difference between strains are insufficient to allow coexistence. Additional heterogeneities in transmission are shown to be necessary to facilitate coexistence of wildtype and modified pathogen strains. We also illustrate how the patterns of infectivity of wildtype and modified strains can also affect long-term coexistence, and argue that appropriate assessment of genetic modifications must be presented in terms of relevant ecological theory.

Animals↗
PubMed2004

Attack rate and success of the parasitoid Diaeretiella rapae on specialist and generalist feeding aphids.

Lipaphis erysimi (Kaltenbach) is a specialist crucifer feeding aphid and Myzus persicae (Sulzer) is a generalist feeding aphid. The foraging behavior of Diaeretiella rapae (McIntosh), a parasitoid with the ability to parasitize both of these species, was assessed using a series of attack rate and success bioassays, with turnip, Brassica rapa var rapifera, as the host plant. The attack rate of D. rapae was significantly greater on L. erysimi than on M. persicae when aphids were feeding on turnip leaf discs in Petri dishes, irrespective of the aphid species upon which the parasitoids were originally reared. Attack rate bioassays with leaf discs absent, using both satiated and starved aphids, revealed that background chemistry and internal aphid chemistry may have small effects on attack rate. Excision of D. rapae pupae from mummy cases and subsequent use of the fully developed adults in attack rate bioassays showed that cues received by D. rapae at the time of adult emergence provide cues that prime D. rapae to attack L. erysimi at a greater rate than M. persicae. However, the relative success of D. rapae on these two aphid species, in terms of the percentage of attacks resulting in a successful adult parasitoid, was not significantly different.

Animals↗
PubMed2003

Drying of Epicoccum nigrum conidia for obtaining a shelf-stable biological product against brown rot disease.

AIMS: The effects of freeze-drying, spray-drying and fluidized bed-drying on survival of Epicoccum nigrum conidia were compared. METHODS AND RESULTS: Viability of E. nigrum conidia (estimated by measuring its germination) was 100% after fluidized bed-drying and freeze-drying, but it was determined that skimmed milk must be added in the case of freeze-drying conidia. Addition of other protectants (Tween-20, peptone, sucrose, glucose, starch and peptone + starch) to skimmed milk before freeze-drying did not improve the conidial viability which was obtained with skimmed milk alone. Glycerol had a negative effect on the lyophilization of E. nigrum conidia. Epicoccum nigrum conidia freeze-dried with skimmed milk, or fluidized bed-dried alone maintained an initial viability for 30 and 90 days, respectively, for storage at room temperature. Epicoccum nigrum conidial viability after spray-drying was lower than 10%. CONCLUSIONS: The best method to dry E. nigrum conidia was fluidized bed-drying. Conidia without protectants dried by this method had 100% viability and survived for 90 days at room temperature. SIGNIFICANCE AND IMPACT OF STUDY: This paper deals with methods for the potential formulation of a biocontrol agent which is being tested for eventual commercialization.

Ascomycota↗
PubMed2005

Increase in toxicity of an invasive weed after reassociation with its coevolved herbivore.

The ability of weeds to proliferate into nonindigenous habitats has been attributed to escape from their native natural enemies, allowing reallocation of resources from chemical defense into growth and reproduction. Many invasive weeds, however, eventually encounter their native, coevolved enemies in areas of introduction. Examination of herbarium specimens of an invasive phototoxic European weed, Pastinaca sativa, through 152 years reveals phytochemical shifts coincident in time with the accidental introduction of a major herbivore, the parsnip webworm, Depressaria pastinacella. Plants collected before the introduction of webworms in North America and during the earliest stages of establishment (1850-1889) are lower in toxic furanocoumarins than all plants subsequently collected in North America and lower than European plant samples collected before 1889. Thus, introduction of a major specialist herbivore can increase noxiousness of a species in its area of introduction, illuminating a potential consequence of classical biocontrol programs involving insect herbivores and poisonous weeds.

Animals↗
PubMed2004

Oxygen- and glucose-dependent regulation of central carbon metabolism in Pichia anomala.

We investigated the regulation of the central aerobic and hypoxic metabolism of the biocontrol and non-Saccharomyces wine yeast Pichia anomala. In aerobic batch culture, P. anomala grows in the respiratory mode with a high biomass yield (0.59 g [dry weight] of cells g of glucose(-1)) and marginal ethanol, glycerol, acetate, and ethyl acetate production. Oxygen limitation, but not glucose pulse, induced fermentation with substantial ethanol production and 10-fold-increased ethyl acetate production. Despite low or absent ethanol formation, the activities of pyruvate decarboxylase and alcohol dehydrogenase were high during aerobic growth on glucose or succinate. No activation of these enzyme activities was observed after a glucose pulse. However, after the shift to oxygen limitation, both enzymes were activated threefold. Metabolic flux analysis revealed that the tricarboxylic acid pathway operates as a cycle during aerobic batch culture and as a two-branched pathway under oxygen limitation. Glucose catabolism through the pentose phosphate pathway was lower during oxygen limitation than under aerobic growth. Overall, our results demonstrate that P. anomala exhibits a Pasteur effect and not a Crabtree effect, i.e., oxygen availability, but not glucose concentration, is the main stimulus for the regulation of the central carbon metabolism.

Acetates↗
PubMed2005

Persistence of Vectobac WDG and Metoprag S-2G against Aedes aegypti larvae using a semi-field bioassay in Rio de Janeiro, Brazil.

Persistence of Bacillus thuringiensis var. israelensis (Vectobac WDG) and methoprene (Metoprag S-2G) was evaluated against Aedes aegypti late third instar larvae of the Rockefeller strain in a semi-field bioassay. Tests were performed in Rio de Janeiro, using containers made of plastic, iron, concrete and asbestos, placed in a shaded area. The formulations used were 0.2 g of Vectobac-WDG and 1 g of Metoprag S-2G per 100 liters of water in house storage containers. Vectobac WDG was tested twice, in March and in April/May, 2002. In March (temperature ranging from 21.5 to 39.3 degrees C), 70-100% mortality was observed by the 7th day and declined abruptly thereafter. No significant differences were observed among the container types. In April/May (18.6 to 34.8 degrees C) mortality was higher than 70% to 30-36 days in all cases, except in the iron container (40% mortality on the 12th day). Metoprag S-2G was evaluated in April/May, 2002, and induced mortality higher than 70% up to 15 days in the plastic and iron containers and only seven days in the concrete container. In the asbestos container, maximal mortality was achieved on day one post-treatment (66%). Our results point to a low persistence of both formulations in the weather conditions of Rio de Janeiro.

Aedes↗
PubMed2000

Biological control agents for white grubs (Coleoptera: Scarabaeidae) in anticipation of the establishment of the Japanese beetle in California.

We tested biological control agents for the control of 3rd-instar scarab turfgrass pests, both for the masked chafer Cyclocephala hirta LeConte and the Japanese beetle, Popillia japonica Newman. The former species is endemic in California whereas the latter, although not yet established, constitutes a permanent serious threat to agriculture and horticulture in California. We conducted experiments using C. hirta in California and P. japonica in New Jersey. A field trial conducted in 2 different California turfgrass sites compared the field persistence in the absence of hosts of Bacillus thuringiensis Berliner subspecies japonensis Buibui strain, the milky disease bacterium, Paenibacillus (=Bacillus) popilliae (Dutky), and the entomopathogenic nematodes Steinernema kushidai Mamiya and Heterorhabditis bacteriophora Poinar to that of the organophosphate diazinon. Soil samples taken 0-70 d after applications were bio-assayed with P. japonica. Only diazinon and the entomopathogenic nematode S. kushidai caused substantial mortality and S. kushidai activity persisted significantly longer than diazinon activity. In greenhouse experiments, combinations of entomopathogenic nematode species usually resulted in additive mortality of scarab larvae. Combinations of S. kushidai and diazinon also resulted in additive mortality. In field trials, the efficacy of H. bacteriophora and especially S. kushidai and S. glaseri, was comparable to that of diazinon over 14-18 d. However, it is likely that at least S. kushidai would have outperformed diazinon over an extended period because of its longer persistence and potential for recycling in the hosts. S. kushidai, should it become commercially available, deserves further examination as an alternative to chemical white grub control especially as a highly compatible component of sustainable turfgrass management.

Animals↗
PubMed1996

Laboratory and field plot bioassay of Bacillus sphaericus against Arkansas mosquito species.

Bacillus sphaericus was evaluated in laboratory bioassays against larvae of 7 Arkansas mosquito species and in rice field plots against a single mosquito species. Laboratory-tested species included Aedes aegypti, Ae. albopictus, Ae. vexans, Anopheles punctipennis, Culex quinquefasciatus, Cx. restuans, and Psorophora columbiae. Field plot bioassays were evaluated against Ps. columbiae only. The laboratory formulation tested demonstrated activity against all 7 species. Mortalities were observed at 24 and 48 h posttreatment. Twenty-four-hour LC50 results ranged from 0.84 to 15.04 international toxic units (ITU)/ml for all species and 48-h LC50 results ranged from 0.38 to 9.27 ITU/ml. Twenty-four-hour LC90 results ranged from 1.90 to 48.21 ITU/ml for all species, whereas 48-h LC90 results ranged from 1.30 to 33.83 ITU/ml. Subsequent field plot evaluations yielded control at both dosages (0.45 and 0.9 g/ ha) during the initial 48-h exposure period. Mortalities at 48 h posttreatment for both dosages were 87 and 90%, respectively. Posttreatment mortalities never exceeded 16.7% after 24 h and none were significantly different from control mortality (P < or = 0.05).

Aedes↗
PubMed2001

Association of PCR and feeding bioassays as a large-scale method to screen tropical Bacillus thuringiensis isolates for a cry constitution with higher insecticidal effect against Spodoptera frugiperda (Lepidoptera: Noctuidae) larvae.

AIMS: To verify whether the presence of any of the cry1C, 1D, 1E and 1F genes could be associated with high toxicity against fall armyworm. METHODS AND RESULTS: A sample of 60 strains from a large collection of tropical Bacillus thuringiensis (B.t.) isolates was subjected to feeding bioassays and gene-specific PCR. Positive amplification of cry-specific fragments, so confirmed by sequencing, revealed that cry1C was ubiquitous and distributed among high and low mortality classes, cry1D was underrepresented and showed no clear association to high toxicity, and cry1F was not detected. The presence of cry1E significantly correlated to high levels of insecticidal activity, as estimated by linear regression analysis. CONCLUSION: The PCR amplification of cry1E-specific fragments alone appears to be sufficient to identify B.t. strains with high mortality levels against tropical armyworm. SIGNIFICANCE AND IMPACT OF THE STUDY: The approach presented is promising as a simple and efficient method for first-tier, marker-assisted screening of environment-specific B.t. germplasm effective in controlling a single target pest.

Animals↗
PubMed2004

Acaricidal activity of plant essential oils against Dermanyssus gallinae (Acari: Dermanyssidae).

The acaricial activity of 56 plant essential oils against poultry house-collected adult Dermanyssus gallinae De Geer was examined using direct contact and fumigation methods. In a filter paper contact bioassay, 100% mortality at 0.07 mgcm-2 was observed in bay, cade, cinnamon, clove bud, coriander, horseradish, lime dis 5F, mustard, pennyroyal, pimento berry, spearmint, thyme red and thyme white oils, whereas the mortality of these oils was significantly decreased at 0.02 mgcm-2. In fumigation tests with adult D. gallinae at 0.28 mgcm-2, cade, clove bud, coriander, horseradish and mustard oils were more effective in closed containers than in open ones, indicating that the effect of these essential oils was largely due to action in the vapour phase. Plant essential oils described herein merit further study as potential D. gallinae control agents.

Animals↗
PubMed1999

Field evaluation of new water-dispersible granular formulations of Bacillus thuringiensis ssp. israelensis and Bacillus sphaericus against Culex mosquitoes in microcosms.

A variety of formulations of Bacillus thuringiensis var. israelensis de Barjac (B.t.i.) and Bacillus sphaericus Neide (B.s.) have been studied for mosquito control under laboratory and field conditions. High efficacy, specificity, low risk of development of resistance, long shelf-life, and transportability, as well as the safety to nontarget organisms of these 2 microbial agents have been well documented. Some of the currently available formulations of B.t.i. and B.s. have low potency per unit mass. Research and development efforts are focusing on commercializing formulations with high potency and low minimum effective dosage that are suitable for long-distance shipment. To achieve this goal, new water-dispersible granule (WDG) formulations of both microbial agents were prepared and made available by Abbott Laboratories for evaluation. The newly developed WDGs of B.t.i. and B.s. with high potency dispersed readily in water with gentle agitation. These WDGs were evaluated and the minimum effective dosages were determined in microcosms against natural populations of Culex mosquitoes. The minimum effective dosage for B.t.i. WDGs with 4,000 International Toxic Units (ITU)/mg was 0.27-0.53 lb/acre which yielded significant control for up to 7-12 days. The minimum effective dosage for B.s. WDGs with 350-630 ITU/mg was 0.05-0.10 lb/acre, which yielded significant control of immature mosquitoes for up to 14-20 days.

Animals↗
PubMed2005

Functional expression of lepidopteran-selective neurotoxin in baculovirus: potential for effective pest management.

Recombinant baculovirus expressing insect-selective neurotoxins derived from venomous animals are considered as an attractive alternative to chemical insecticides for efficient insect control agents. Recently we identified and characterized a novel lepidopteran-selective toxin, Buthus tamulus insect-selective toxin (ButaIT), having 37 amino acids and eight half cysteine residues from the venom of the South Indian red scorpion, Mesobuthus tamulus. The synthetic toxin gene containing the ButaIT sequence in frame to the bombyxin signal sequence was engineered into a polyhedrin positive Autographa californica nuclear polyhedrosis virus (AcMNPV) genome under the control of the p10 promoter. Toxin expression in the haemolymph of infected larvae of Heliothis virescens and also in an insect cell culture system was confirmed by western blot analysis using antibody raised against the GST-ButaIT fusion protein. The recombinant NPV (ButaIT-NPV) showed enhanced insecticidal activity on the larvae of Heliothis virescens as evidenced by a significant reduction in median survival time (ST50) and also a greater reduction in feeding damage as compared to the wild-type AcMNPV.

Animals↗
PubMed2004

Development and reproduction of Podisus distinctus (Heteroptera: Pentatomidae) fed on larva of Bombyx mori (Lepidoptera: Bombycidae).

Biological control has been reducing the use of chemical products against insect pests, especially predatory Pentatomidae. Species of this group can present high variations in their life cycle as a result of their diet. Thus, the objective of this research was to study nymph development and reproduction of Podisus distinctus (Stäl, 1860) (Heteroptera: Pentatomidae) fed on Bombyx mori L., 1758 (Lepidoptera: Bombycidae) larvae (T1), compared to those fed on Tenebrio molitor L., 1758 (Coleoptera: Tenebrionidae) (T2) and Musca domestica L., 1758 (Diptera: Muscidae) larvae (T3) at a temperature of 25 +/- 0.5 degrees C, relative humidity of 70 +/- 2%, and photophase of 12 h. Predators fed on B. mori showed duration of the nymph phase (18.68 +/- 1.02) similar to those fed on T. molitor (18.32 +/- 1.49). Pre-oviposition and oviposition periods and number of egg masses, besides eggs and nymphs per female, were higher with B. mori (5.83 +/- 2.02; 15.00 +/- 7.40; 8.42 +/- 1.84; 296.69 +/- 154.75; and 228.55 +/- 141.04, respectively) while longevity of males and females of P. distinctus was 25.76 +/- 16.15 and 35.00 +/- 16.15 days with T. molitor, and 20.57 +/- 13.60 and 23.46 +/- 12.35 days with B. mori, respectively.

Animals↗