Zur Wirksamkeit vonBeauveria bassiana (Bals.) Vuill. gegenHylobius abietis L. [Col.: Curculionidae]

Zusammenfassung Um die Wirksamkeit einesBeauveria bassiana-Pr?parates gegenHylobius abietis zu überprüfen, wurden die Versuchstiere mit Sporenstaub und Sporensuspension behandelt und bei 13°, 23° und 33°C (bei Futterangebot bzw. Hunger) gehalten. 33°C erwies sich in allen Versuchen für die K?fer als zu hoch (100% Mortalit?t nach 2 Wochen) bei gleichzeitiger Reduktion von Pilzsporenkeimung und Hyphenwachstum. Bei 23 °C wurden dagegen bei mittlerer Lebensdauer (bei Sporenstaub 8,2 Tage und bei Sporensuspension 21,5 Tage) h?chste Infektionsraten erzielt (86,9 bzw. 100 %). Obwohl die kontaminierten K?fer bei 13 °C am langsamsten starben (ohne Futter: nach Sporenstaub 12,9 und 18,9 Tage nach Sporensuspension, mit Futter: 72,3 bzw. 86,6 Tage mittlere Lebensdauer) erkrankte auch hier ein sehr hoher Prozentsatz (55 % nach Sporenstaub, mit Futter und 91,4 % nach Sporensuspension, ohne Futter). Die Verwendung von verdünnten Sporenst?uben brachte eine deutliche Abstufung der Mortalit?tsgeschwindigkeit in Abh?ngigkeit von der applizierten Sporenmenge. Sporendosen unter 3×10⁴ Konidien/K?fer erwiesen sich auch nach 8 Wochen als wenig wirksam, solche von etwa 4×10⁷ Konidien/K?fer dagegen erzielten schon nach 2 Wochen h?chste Sterberaten bei gleichzeitig 100 % Infektion mitb. bassiana. Mit Sporenstaub kontaminiertes Futter (1,17×10⁸ Konidien/cm² Rinde) führte bei niedrigen Infektionsraten etwa gleich schnell zu 100 % Mortalit?t wie direkte Kontamination der K?fer. Das Angebot st?rker kontaminierten Futters (5,83×10⁸ Konidien/cm² Rinde) über nur 3 Tage führte trotz anschlie?ender Versorgung mit unbehandeltem Frischfutter, bei langsamer Sterblichkeit zu einer 100 prozentigen Infektion der Versuchstiere. Fangrinden die in einem Freilandexperiment mitB. bassiana behandelt worden waren, zeigten eine ungeminderte Lockwirkung, bewirkten jedoch nur geringe, unmittelbare Sterblichkeit. Die hohenB. bassiana-Infektionsraten in den Laborexperimenten k?nnten bei einer praktischen Anwendung unter günstigen Bedingungen auch im Freiland langfristig zu Erfolgen führen.      

Horizontal transmission of Beauveria bassiana (Bals.) Vuill

1 Factors influencing horizontal transmission of the entomopathogen Beauveria bassiana in the Colorado potato beetle (CPB) were examined through a series of laboratory studies. 2 Cadaver density, cadaver life stage, ambient temperature and conidial density were the factors manipulated. 3 Mortality and sporulation of burrowing CPB prepupae both increased significantly with increased sporulating second‐instar cadaver density on the soil surface. 4 Mortality rates were significantly higher when prepupae were released into laboratory arenas containing third‐instar cadavers compared to second‐instar cadavers. 5 Mortality and sporulation decreased significantly as temperature increased from 15 °C to 30 °C, however, no temperature‐dependent behavioural response by prepupae could be identified as a potential cause. 6 An 86.1% decrease in conidial density per cadaver had no significant effect on mortality or sporulation of prepupae, indicating that this level of environmental degradation of cadavers may not significantly reduce the probability of horizontal transmission.     

Vorversuche zur Massenkultur vonBeauveria bassiana (bals.) vuill. undSpicaria farinosa (fr.) Vuill.

Ohne Zusammenfassung     

Physiological and antioxidant response by Beauveria bassiana Bals (Vuill.) to different oxygen concentrations

The effect of three levels of oxygen (normal atmosphere (21% O₂), low oxygen (16% O₂) and enriched oxygen (26% O₂)) on the production and germination of conidia by Beauveria bassiana was evaluated using rice as a substrate. The maximum yield of conidia was achieved under hypoxia (16% O₂) after 8 days of culture (1.51 × 10⁹ conidia per gram of initial dry substrate), representing an increase of 32% compared to the normal atmosphere. However, germination was reduced by at least 27% due to atmospheric modifications. Comparison of antioxidant enzyme activity (superoxide dismutases and catalases) with the oxidation profiles of biomolecules (proteins and lipids) showed that a decrease in catalase activity in the final days of culture coincided with an increase in the amount of oxidized lipids, showing that oxidative stress was a consequence of pulses of different concentrations of O₂. This is the first study describing oxidative stress induction by atmospheric modification, with practical implications for conidia production.     

Cosmopolites sordidus (Germar) susceptibility to indigenous Cameroonian Beauveria bassiana (Bals.) Vuill. and Metarhizium anisopliae (Metsch.) isolates

Management of the banana root borer (BRB), Cosmopolites sordidus (Germar; Coleoptera: Curculionidae), remains a challenge in banana and plantain production worldwide. Synthetic pesticides remain the most widely used solution while mycoinsecticides are increasingly being recommended. In this study, we selected indigenous isolates of Beauveria bassiana and Metarhizium anisopliae collected from plantain fields in Cameroon, and tested them in the laboratory for their viability, pathogenicity and virulence against all C. sordidus life stages. Of 13 isolates initially screened for spore germination and pathogenicity to adult weevils in conidial suspension of 3.2 × 10⁸ conidia/ml, eight isolates with high to moderate germination and highest weevil mortality were selected for dose–response bioassays with four concentrations per isolate: 3.2 × 10², 3.2 × 10⁴, 3.2 × 10⁶ and 3.2 × 10⁸ conidia/ml. The virulent isolates from adult bioassays were tested with eggs, larva and pupae in conidial suspension of 3.2 × 10⁸ conidia/ml. Isolates performance depended on insect life stage with significantly high pathogenicity and virulence against larval, pupa and adult stages. The Beauveria isolate BIITAC6.2.2 caused the highest mortality rates followed by MIITAC1.1.5. Lethal times and lethal concentrations were relatively low for the three M. anisopliae isolates and three B. bassiana isolates which were the best isolates in almost all insect life stages. Apart from being effective in multiple life stages, these isolates were transmitted horizontally from one stage to another when eggs and pupae were treated. The implication of these findings for integrated management of the BRB, and potential biopesticides development and commercialization are discussed.     

Untersuchungen über die Wirkung der Insektentötenden PilzeBeauveria bassiana (Bals. Vuill.) undMetarrhizium anisopliae (Metsch.) Sorok. auf Warmblütler

Summary The muscardine-fungi are nor toxic neither pathogen for man and warmblooded animals. Reactions of sensitive persons working with spores of this fungi are not of general but of allergic nature. Against such allergic reactions it is possible to protect by breath protection, dress with long sleeves and gloves.      

森林生态系中球孢白僵菌遗传多样性的ISSR分析

应用ISSR分子标记对安徽大别山区的球孢白僵菌遗传多样性进行了研究。从33个引物中筛选出12个多态性高、稳定性好的ISSRs用于正式的扩增分析,在2个自然保护区、3个不同季节和3个不同海拔梯度采集的48个菌株中共扩增出84条带,其中73条为多态性条带,多态性为81％,平均每个引物扩增出7条（2～11）。群体的多态位点百分率（PPL）达81％,Nei’s基因多样性（H）为0.3187,Shannon信息指数（I）为 0.4782。居群间的基因分化系数较小（Gst）0.1028。以上结果表明：安徽大别山区球孢白僵菌有较高的遗传多样性, 居群间遗传变异较小,居群内表现出较高水平的遗传分化。     

Efficacy of Beauveria bassiana (Bals.) Vuill. against the tarnished plant bug, Lygus lineolaris L., in strawberries

Beauveria bassiana has a high insecticidal potential to control the tarnished plant bug, Lygus lineolaris, a significant pest of strawberries. Screening experiments showed that L. lineolaris adults were susceptible to several B. bassiana isolates. Another screening test with Coleomegilla maculata, a natural enemy found in strawberries, was also performed in order to select the isolate having lower entomopathogenic impact on this insect. Based on data obtained from both insect species and on the ecozone origin of the B. bassiana isolates, INRS‐IP and INRS‐CFL isolates were selected for further experiments. The LC₅₀ values of these two isolates against L. lineolaris adults were 7.8 × 10⁵ and 5.3 × 10⁵ conidia/ml, and average survival time (AST) values were 4.46 and 4.37 days at a concentration of 1 × 10⁸ conidia/ml respectively. Results also indicated that L. lineolaris nymphs are susceptible to the selected isolates. During field experiments, using a randomized block design with four replicates, INRS‐IP and INRS‐CFL isolates were applied at two rates (1 × 10¹¹ and 1 × 10¹³ conidia/ha) weekly during a period of 4 weeks. These multiple applications triggered a significant reduction of L. lineolaris nymphal populations in strawberries. Twenty‐four days after the first application, a significant difference was observed between the mean population densities of surviving nymphs in all B. bassiana‐treated plots (less than one insect per five plants) compared with those in control plots (four insects per five plants). During the field experiment, persistence of insecticidal activity and viability of B. bassiana conidia were also monitored. The results showed the presence of viable and infective conidia up to 6 days after each application on strawberry foliage. Moreover, the multiple applications of B. bassiana at the rate of 1 × 10¹³ conidia/ha triggered a significant reduction in strawberry fruit injuries induced by L. lineolaris feeding behaviour compared with the control plots.     

Selection of Beauveria bassiana (Bals.) Vuill. and Metarhizium anisopliae (Metsch.) Sorok. isolates against Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae)

This study was carried out to evaluate entomopathogenic fungi isolates as microbial control agents ofthe lesser mealworm, Alphitobius diaperinus (Panzer). Larvae and adults were inoculated with conidial suspension of 99 isolates of Beauveria bassiana (Bals.) Vuill. and Metarhizium anisopliae (Metsch.) Sorok. (10(5) to 10(9) conidia/ml). Vegetative growth on culture media and sporulation on culture media, cooked rice and lesser mealworm cadavers were also evaluated. Isolates of B. bassiana were more effective than the M. anisopliae isolates and larvae were more susceptible than adults. The isolates UNIOESTE 04 and UNIOESTE 02 were originally obtained from adults of the lesser mealworm and were the most efficient isolates. In addition, UNIOESTE 04 showed high level of sporulation on different culture media and is considered a potential useful tool to lesser mealworm control.     

Field evaluation of the efficacy of neem oil (Azadirachta indica A. Juss) and Beauveria bassiana (Bals.) Vuill. in cotton production

Neem oil (Azadirachta indica A. Juss) alone and combined with the entomopathogenic fungus Beauveria bassiana (Balsamo) Vuillemin (isolate Bb11) was applied to control cotton pests. The efficacy of these treatments was compared with that of synthetic insecticides applied either in a calendar‐based application or in the ‘Lutte Etagée Ciblée’ (LEC) strategy, consisting of using first calendar‐based (half‐dose) applications followed by threshold‐based treatments. The experiment was carried out in collaborative research with farmers in three cotton agro‐ecological zones differing in rainfall, pest prevalence, and farming practices. The neem oil and neem oil‐Bb11 treatments required 2 to 6 applications, while conventional and LEC received 6 to 8 applications. The percentage of damaged reproductive organs in plots treated with neem oil and neem oil plus Bb11 was higher than that recorded under the conventional and LEC strategy, with exception of the zone with the highest rainfall; this resulted in yields being 25% and 39% lower, respectively. Yields in the biopesticide plots were 26–42% higher and in the conventional and LEC plots 44–59% higher than those in the control plots that received only water. Overall, the LEC regime scored best, both in yield and profitability. The incidence of natural enemies was highest in the control and in the plots treated with biopesticides. Although the use of entomopathogen Bb11 and neem oil avoids many problems associated with the application of synthetic insecticides, their efficacy needs to be enhanced by improved formulation or by combining them with other pesticides.     

Effects of Metarhizium anisopliae (Metsch.) Sorok. and Beauveria bassiana (Bals.) Vuill. on the predatory stinkbug Podisus nigrispinus (Dallas) (Hemiptera: Pentatomidae)

Entomopathogenic fungi and the predatory stinkbug Podisus nigrispinus (Dallas) can target simultaneously the same or different pests in agroecosystems. Topical contact during fungal dispersion or spraying, walking on plant surfaces and ingestion of contaminated prey are some of possible ways of interactions between fungi and the predatory stinkbug. The impact of three isolates of Metarhizium anisopliae (Metsch.) Sorok. (866, 1022 and 1189) and Beauveria bassiana (Bals.) Vuill. (604, 634 and 561) against nymphs and adults of P. nigrispinus was investigated under laboratory conditions. M. anisopliae caused higher mortality compared to B. bassiana either by topical application or by dry residue on cotton leaves. Topic contact with both fungi caused higher mortality to the predator. No mortality confirmation was reported for the adults. Nymphs fed with cotton leafworm larvae Alabama argillacea (Hübner) (Lepidoptera: Noctuidae) contaminated by the fungi had their reproduction affected, but this was not observed when adult predators fed on contaminated larvae. These findings suggest that isolates of M. anisopliae can cause mortality of P. nigrispinus nymphs by topical contact, while isolates of B. bassiana were less harmful by all ways of infection as compared to M. anisopliae.     

Biocontrol of almond bark beetle (Scolytus amygdali Geurin-Meneville, Coleoptera: Scolytidae) using Beauveria bassiana (Bals.) Vuill. (Deuteromycotina: Hyphomycetes)

AIMS: To formulate the entomopathogenic fungus Beauveria bassiana in invert emulsion, then apply it against adults of almond bark beetle (Scolytus amygdali) under laboratory and field conditions. METHODS AND RESULTS: The effect of formulated B. bassiana in invert emulsion against S. amygdali adults was shown by comparing the mortality percentage of adults exposed to the formulated fungus using a Petri dish treatment method and by field applications to infested peach trees with mortality of adults exposed to the unformulated fungus or the untreated control. Results obtained from both exposure methods have indicated that treatment of S. amygdali adults with the formulated fungus resulted in a significantly higher mean mortality percentage (P < 0.05) when compared with the treatment with the unformulated fungus or the untreated control. This mortality ranged from 81.2 to 100%, 10 days after treatment with the formulated fungus when compared with 6.7 to 49.6% mortality, 10 days after treatment with the control or the unformulated fungus, respectively. Viability of the fungus conidia in invert emulsion was assessed by calculating the germination percentage of the conidia over time. Results indicated a high storage stability shown by a small loss of germination percentage for the formulated conidia of both strains (5.8 to 8.4% over a 12-week period) vs a low storage stability shown by a high loss of germination percentage for the unformulated conidia of the same strains (58.9 to 61.0% over the same period). The presence of B. bassiana in the galleries of beetles following the treatment of infested trees was shown in the present research. CONCLUSIONS: The results obtained have demonstrated a significantly higher level of efficacy of formulated B. bassiana in invert emulsion against S. amygdali adults under laboratory and field conditions. The ingredients of invert emulsion used in the formulation of the fungus had a negligible effect on the viability of formulated conidia when compared with the unformulated. SIGNIFICANCE AND IMPACT OF THE STUDY: Results obtained in the present research are promising and may be exploited commercially to control S. amygdali adults on various species of stone fruit trees, especially peach trees. This type of biocontrol of this insect may be used as an alternative means to chemical control for management of the insect. No adverse environmental impacts of the fungus or its formulation have been observed during application.     

Efficacy of Beauveria bassiana (Bals.) Vuill. against the spruce bark beetle, Ips typographus L., in the laboratory under various conditions

Abstract:  In laboratory bioassays, the efficacy of the entomopathogenic fungus Beauveria bassiana against the spruce bark beetle, Ips typographus , was tested under various conditions. Four of the tested isolates and the commercial product Boverol^® caused 99–100% mortality when tested at a concentration of 1.0 × 10⁷ conidia/ml at 25°C. Using B. bassiana isolate 138 at a concentration of 1.0 × 10⁶, the median survival time (MST) was 6.1 d and significantly longer compared with the MST of 4.2 and 4.0 d at 1.0 × 10⁷ and 1.0 × 10⁸ conidia/ml, respectively. In the next experiment, the beetles were maintained on spruce bark, filter paper or artificial diet during the bioassay with Boverol^®, and significant differences in the MST of 3.6, 2.5 and 5.3 d, respectively, were noticed. The experiment with Boverol^® at different temperatures showed that the beetles lived significantly longer at 15°C (MST 8.7 d) than at 20, 25, 30 and 35°C. At 25°C, the beetles died most rapidly (MST 3.5 d). At different relative humidities (RH) of 40, 70 and 100%, nearly all beetles were dead after treatment with a suspension of Boverol^® at 1.0 × 10⁷ conidia/ml. At 40% RH, 49% of the untreated beetles died after 7 d. The best effects were achieved with the following bioassay: beetles were fed for three days on artificial diet, then dipped into a solution of 1.0 × 10⁷ conidia/ml and transferred on a piece of spruce bark in Petri dishes at 25°C and 70% RH.     

Exchange of Inoculum of Beauveria bassiana (Bals.) Vuill. (Hyphomycetes) Between Adult Flies of the Cabbage Maggot Delia radicum L. (Diptera: Anthomyiidae)

Adult cabbage maggots ( Delia radicum L.) were exposed to dry conidia of isolates of several hyphomycetous fungi by placing them in a centrifuge tube containing conidia, then releasing them into small screened plastic cages. Mortality was assessed after 48, 120 and 160 h. A Beauveria bassiana isolate (P89 from Musca domestica ) caused the highest mortality after 48 h, resulting in 100% mortality and 100% infection. Isolate L90 ( B. bassiana ) and one Metarhizium anisopliae isolate (ARSEF 2521) also caused fatal infection in more than 50% of the flies. To investigate exchange of inoculum, flies were placed in a small container with a dry powder formulation containing B. bassiana (Mycotrol ® ) on the bottom. The flies were removed to small screened cages containing untreated flies. This experiment confirmed the ability of flies to pass inoculum to other flies. In a similar experiment, one treated fly was placed in each cage with one untreated fly. When each fly died, one untreated fly was added to each cage after the dead fly was removed. This study showed that fly to fly transfer of fatal doses of inoculum was possible for a series of at least six flies. When female flies were exposed to the inoculum, then transferred to small cages containing males and an oviposition substrate, no eggs were laid. Further studies are being conducted to develop a system where flies attracted to a trap will be inoculated with the fungus and spread it to a field population.     

Insecticidal efficacy of two isolates of Beauveria bassiana (Bals.) (Vuill.), on the second larval stage of Leptinotarsa decemlineata (Say) (Col.: Chrysomelidae)

Leptinotarsa decemlineata is a serious potato pest throughout the world that has developed resistance to many insecticides. This study investigated the virulence of two indigenous isolates of Beauveria bassiana, consisting of DEBI007 and IR1217C. Five different concentrations of each isolate, 1 × 10⁷, 3.1 × 10⁷, 1 × 10⁸, 3.1 × 10⁸ and 1 × 10⁹ conidia ml^?1, were applied in bioassay using dipping method on second instar larvae. Control insects were treated with distilled water containing 0.01% Tween-80 (Sigma, Germany) as surfactant. The results showed that mortality percentages due to DEBI007 and IR1217C isolates in the highest concentration were 60% and 57.77%, respectively. There was a significant difference between efficacies of different conidial concentrations; therefore, with rise in conidial concentration, the mortality percentage was increased. The DEBI007 isolate that was previously isolated from the soil was more effective than IR1217C isolate. Calculated LC₅₀ for this effective isolate was 1.4 × 10⁷ conidia ml^?1, which, respectively, is the highest concentration.     

Processus pathologiques consécutifs a l'action deBeauveria bassiana (Bals.)Vuill. associé a de faibles doses de D.D.T., chezLeptinotarsa decemlineata Say

Summary The high efficacy of the fungusBeauveria bassiana (Bals.) Vuill. in addition to small doses of insecticides in the control of Colorado Beetle larvae seems to be the result of a joint-action on the insect of the insecticide, the fungus and the intestinal microflora which are combined in the pathological process. A part of the population is directly killed by the insecticide, another part by the septicemy provoked by the occasionally pathogenous bacteria, the last part dies by muscardine. Consequent upon the influence of the pathogenous microorganisms, the pH variations of the haemolymphe of the larvae seems to be the factor of the physiological weaking of the insect's organism which permits the development of the disease.      

Allee Effect in the Infection Dynamics of the Entomopathogenic Fungus Beauveria bassiana (Bals) Vuill. on the Beetle, Mylabris pustulata

Successful infection by Beauveria bassiana as with all other entomopathogenic fungi, is accomplished only at a high conidial dose while, theoretically, a single conidium should be sufficient. Indeed, this is a major deterrent in its use as a biocontrol agent. High pathogen load for infection is required by organisms which display ‘Allee’ effect. In such organisms, a threshold exists for pathogen dose, below which no infection can be caused. B. bassiana has a semelparous life cycle and, therefore, its infection dynamics are expected to conform to the mass action principle with a linear relationship between dose and successful infection observable as mortality of the insect. Whether the need for a high conidial dose to induce insect mortality by B. bassiana is due to the operation of Allee effect was examined. A sample of 34 isolates was bioassayed on Mylabris pustulata (Coleoptera: Meloidae) at four conidial concentrations. With more than half of the isolates in the sample, the lowest dose tested (10⁴ conidia/insect) did not cause insect mortality. Thus, a threshold pathogen load is required to cause successful infection. In these isolates, the dose–mortality relationship was sigmoid. Allee effect is thus identified in the infection dynamics of B. bassiana–M. pustulata system. The isolates that induced mortality at the lowest dose tested are concluded to be highly virulent with a lower threshold dose required for successful infection. With some isolates, at high conidial dose, the infection rate decreased either due to a decrease in the proportion of insects showing mycosis, to the speed of death, or both. Such a response could result from intra scramble competition arising from overload of pathogen at very high dose.