Efficacy of biorational insecticides against chilli thrips,Scirtothrips dorsalis (Thysanoptera: Thripidae), infesting roses under nursery conditions

We evaluated biopesticides based on entomopathogenic fungi, azadirachtin and horticultural oils for the management of the chilli thrips, Scirtothrips dorsalis Hood, an economically significant invasive pest in the United States. Insecticides were applied four times at 7‐ to 10‐day intervals against established S. dorsalis infestations on shrub roses KnockOut^®, Rosa x ‘Radrazz’ under simulated nursery conditions. When applied as stand‐alone treatments, Beauveria bassiana GHA (BotaniGard^® ES), Metarhizium brunneum F52 (Met‐52 EC), a horticultural oil (SuffOil‐X^®) and azadirachtin (Molt‐X^®) at label rates provided significant control, reducing populations of S. dorsalis by 48–71% compared with control over 4–6 weeks. Similar results were observed when the biopesticides were applied in rotation with each other. A conventional standard, spinosad (Conserve^® SC), was consistently the most effective treatment in these studies, reducing thrips populations by >95% overall. In another study, more effective control (87%–92%) was achieved in biopesticide rotation programmes that included spinosad, when compared with those that did not. Results also showed that these biopesticides can be tank‐mixed. However, there was no evidence that B. bassiana or M. brunneum combined with azadirachtin resulted in additive or synergistic control, as neither tank‐mix treatment improved control compared with azadirachtin alone. These findings highlight the potential use of biopesticides in rotation programmes with conventional insecticides to manage S. dorsalis on roses. Biopesticides evaluated in this study can be incorporated into an IPM programme for roses.     

Immunity of the greater wax moth Galleria mellonella

Investigation of insect immune mechanisms provides important information concerning innate immunity, which in many aspects is conserved in animals. This is one of the reasons why insects serve as model organisms to study virulence mechanisms of human pathogens. From the evolutionary point of view, we also learn a lot about host–pathogen interaction and adaptation of organisms to conditions of life. Additionally, insect‐derived antibacterial and antifungal peptides and proteins are considered for their potential to be applied as alternatives to antibiotics. While Drosophila melanogaster is used to study the genetic aspect of insect immunity, Galleria mellonella serves as a good model for biochemical research. Given the size of the insect, it is possible to obtain easily hemolymph and other tissues as a source of many immune‐relevant polypeptides. This review article summarizes our knowledge concerning G. mellonella immunity. The best‐characterized immune‐related proteins and peptides are recalled and their short characteristic is given. Some other proteins identified at the mRNA level are also mentioned. The infectious routes used by Galleria natural pathogens such as Bacillus thuringiensis and Beauveria bassiana are also described in the context of host–pathogen interaction. Finally, the plasticity of G. mellonella immune response influenced by abiotic and biotic factors is described.     

Mycelia and spent fermentation broth of Beauveria bassiana incorporated into synthetic diets affect mortality,growth and development of larval Helicoverpa zea (Lepidoptera: Noctuidae)

Beauveria bassiana endophytically colonises corn (Zea mays) reducing tunneling from European corn borer (Ostrinia nubilalis). Endophytic colonisation of other plants by B. bassiana has been reported, and potentially, may reduce insect feeding on these plants. We evaluated the effects on larval growth and development, and mortality of different rates of dried, ground mycelia and water-soluble metabolites from fermentation broth culture of different isolates of B. bassiana incorporated into a synthetic diet and fed to neonate bollworm, Helicoverpa zea larvae. Development was delayed, weights of larvae were lower, and mortality was high for larvae fed the highest rates (1.0 and 5.0%, w/v) of mycelia incorporated diet compared to control. Insects fed diets containing mycelia of B. bassiana isolate 11-98 had the greatest mortality. Mortality was 100% for larvae fed 5% (w/v) mycelia incorporated diet of isolate 11-98, and 61% for isolate 3-00. For insects fed low rates (0.1 to 0.5%, w/v) of mycelia incorporated diet, mortality was lower, approximately 5% for isolate 11-98, and 5 to 14% for isolate 3-00. At the 0.1% (w/v) rate of mycelia incorporated diet, development occurred at an accelerated rate, compared to fungus-free controls, indicating increased nutrition in the lowest rate fungal diet. Mortality was low for all larvae fed diets containing spent fermentation broth of B. bassiana; however, development was delayed. Insects fed the highest rate (0.5%, v/v) of spent fermentation broth-amended diet had lower pupal weights, and a greater number of days to pupation than insects fed the lowest (0.1%, v/v) rate. Insects fed the 5% (v/v) rate of spent fermentation broth of isolates 11-98 and 3-00 had the longest days to pupation.     

A cuticle-degrading protease (CDEP-1) of Beauveria bassiana enhances virulence

In order to investigate virulence enhancement of entomopathogenic fungi, a Beauveria bassiana-sourced Pr1 protease (CDEP-1) was expressed by a methylotrophic yeast Pichia pastoris and then used as an additive to three gradient sprays of B. bassiana strain (Bb0062) onto apterous green peach aphid Myzus persicae adults in six bioassays. The resultant data fit well to a time–concentration–mortality model. Generally, the LC₅₀ estimates of the fungal pathogen against the aphid species decreased with increasing CDEP-1 concentrations from 0 to 100 µg mL^?1. The LC₅₀s on days 5–7 after spray were reduced by 1.5–2.5-fold at the concentrations of 20–100 µg mL^?1. However, sprays of 20–100 µg CDEP-1 mL^?1 aqueous solution alone had no significant effect on aphid mortality compared to water spray only. Neither did inclusion of inactivated CDEP-1 at a concentration of 50 µg mL^?1 affect significantly the fungal virulence to aphids. Our results confirm for the first time that the cuticle-degrading protease CDEP-1 enhanced fungal virulence due to acceleration of conidial germination and cuticle penetration. This suggests a new approach to utilising the protease in microbial control.     

Microbial control of Agrilus planipennis (Coleoptera: Buprestidae) with Beauveria bassiana strain GHA: field applications

The effects of Beauveria bassiana strain GHA, applied as BotaniGard ES, on newly colonised and well-established populations of emerald ash borer, Agrilus planipennis (Coleoptera: Buprestidae) were evaluated in the field using foliar and trunk sprays in Michigan in 2004–2005. Results from field trials at a newly colonised white ash site showed a 41% reduction in A. planipennis population in fungal-treated trees compared with that of untreated controls. In addition, fungal infection was also found in 20% of the larval population within 14 days of incubation under laboratory conditions. At a site with a well-established Agrilus planipennis population in green ash trees, larval density was reduced by 47% for trees treated with the fungus compared with that of the controls; 21% of larvae from the current generation were found infected after 14 days of laboratory incubation. Fungal-treated green ash trees also produced fewer adults emerging in the next generation, with a 63% reduction in adult density observed in treated trees compared to that of controls. As a result, fungal-treated trees sustained 42% less crown dieback than did controls. A. planipennis larval density was negatively correlated with trunk height above the ground, and positively correlated with log diameter. Results of laboratory leaf bioassays on A. planipennis adults showed that fungal conidia persisted well under field conditions, with mortality of 78–100% at 7 – days post – exposure for leaves collected between 2 and 264 h after application. Potential strategies for using B. bassiana strain GHA for managing A. planipennis are discussed.     

Comparing formulations for a mixed-microbial biopesticide with Bacillus thuringiensis var. kurstaki and Beauveria bassiana blastospores

Developing a dual agent biopesticide formulation made with blastospores of Beauveria bassiana (Balsamo) Vuillemin strain GHA (Bb) at the ratio of 1:1 mixed with traditional fermentation production of Bacillus thuringiensis kurstaki (Btk) spores and crystals were studied. Twelve potential formulation ingredients were screened for their impact on insecticidal activity, microbe viability, UV protection and product suspensibility of a spray dried Bt/Bb (1:1) mixture applications to cabbage plants against cabbage looper, Trichoplusia ni. Based on the results, Spray-dried mixtures of Bt/Bb made with biochar, chitosan and skim milk powder formulations gave the greatest efficacy and higher solar stability when exposed to simulated sunlight. They therefore can be used as a formulation that combines Bt with Bb in one product. However, the formulation made with aitkin component had significantly more colony forming units (CFUs) of Bt, whereas, formulations made with albumin, sodium carbonate and pharmamedia had more Bb CFUs than other formulations. Albumin, pharmamedia, skim milk powder and biochar had significantly better suspension in water (less settling) than others. These results support the concept of formulating the two biocontrol agents, B. thuringiensis and B. bassiana blastospores for greater efficacy, more viability and longer field persistence as an environmentally friendly sustainable pest control tool.

LSID:urn:lsid:zoobank.org:pub:568D6FE6-E876-417B-BE39-C51F7CBAD6AB     

Species confirmation of fungal isolates by molecular analysis

Traditional taxonomy of hyphomycetes has been based on conidial morphology and development. In order to confirm species level for the detection and identification of the entomopathogenic fungus, we analysed the species-specific fingerprints to investigate molecular characteristics within isolates of six species and to resolve morphologically atypical isolates. The extent of fingerprint profile observed by RAPD was sufficient to confirm the species level of all the isolates. The genetic similarity among morphologically identified isolates of each species was considerably higher, allowing us to conclude that all the isolates are of same species. These results establish a molecular framework for further taxonomic, phylogenetic and comparative biological investigations.     

Culture conditions affect virulence and production of insect toxic proteins in the entomopathogenic fungus Metarhizium anisopliae

Conidial spores are often used as the infectious agent during insect biocontrol applications of entomopathogenic fungi. Here we show differential virulence of conidia derived from Metarhizium anisopliae strain EAMa 01/58-Su depending upon the solid substrata used for cultivation, where LC₅₀ values differed by up to ~10-fold (5.3×10⁶?4.5×10⁵ conidia/ml) and LT₅₀ values by ~40% (9.8?7.1 d). This fungal strain is also known to secrete proteins that are toxic towards adult Mediterranean fruit flies, Ceratitis capitata, and the Greater wax moth, Galleria mellonella, larvae. In vitro production and intrahemoceol injection using G. mellonella as the host was used to test fractions during purification of the protein toxins, demonstrating that they elicited defence-related responses including melanisation and tissue necrosis. Production of these proteins/peptides along with a number of potential cuticle degrading enzymes was confirmed both in vitro and during the infection process (in vivo). Two-dimensional gel electrophoresis, followed by gel elution and bioassay, was used to identify at least three proteins or peptides (molecular mass=11, 15 and 15 kDa) as mediating the observed insect toxicity. These data demonstrate that in vitro screening for insect toxins can mimic in vivo (i.e. during the infection process) secretion and applies the use of proteomics to invertebrate pathology.     

House flies delay fungal infection by fevering: at a cost

1. Many ectothermic species have evolved the ability to invoke a ‘behavioural fever’ when infected with a pathogen. The relative costs and benefits of this response, however, have rarely been quantified. 2. The aim of this study was investigate the nature and consequences of behavioural fever in the house fly, Musca domestica L., in response to infection with a possible biocontrol agent, the fungal entomopathogen, Beauveria bassiana (Balsamo) Vuillemin. 3. It was found that infected flies preferred higher temperatures and allocated more effort to thermoregulation than uninfected flies. Flies could not overcome infection but the altered thermal behaviour allowed infected flies to extend their survival and to lay more eggs relative to infected flies maintained under constant conditions. However, flies allowed to fever had lower egg viability suggesting a possible cost. 4. Under the present experimental conditions, the putative costs and benefits fever balanced one another resulting in no net change in fitness. Fever did not, therefore, limit the control potential of the fungus. We discuss whether the costs and benefits of behavioural fever might differ in other ecological contexts.     

球孢白僵菌对四种十字花科蔬菜害虫的兼控潜力评价

研究了分离自小猿叶甲的一株球孢白僵菌(Beauveria bassiana(SCAU-BB01D))对十字花科蔬菜4种非目标害虫烟粉虱Bemisia tabaci、小菜蛾Plutella xylostella、黄曲条跳甲Phyllotreta striolata和菜缢管蚜Lipaphis erysimi的致病能力。结果表明,在实验室条件下,该菌株对以上4种害虫均有不同程度的侵染力。1×108孢子/mL的白僵菌悬浮液对1,2,3,4龄烟粉虱若虫的侵染率分别为84.88,86.81,55.94和38.78%;对小菜蛾2,3和4龄幼虫的侵染率为67,59和44%;对黄曲条跳甲幼虫和成虫分别为63%和60%;对菜缢管蚜成蚜和若蚜的侵染率分别为44%和35%。通过机率值分析,得出该菌株对烟粉虱1~4龄若虫的LT50分别为4.14,3.78,6.24和7.59 d;对小菜蛾2~4龄幼虫的LT50分别为7.29,8.16和9.82d;对黄曲条跳甲成虫和幼虫的LT50分别为11.22和8.11 d;对菜缢管蚜成蚜和若蚜的LT50分别为11.01和12.15 d。说明该球孢白僵菌菌株对烟粉虱、小菜蛾和黄曲条跳甲3种非目标害虫具有一定的兼控作用,在蔬菜害虫的生物防治中具一定的应用潜力。