Predacious activity of Duddingtonia flagrans within the cattle faecal pat

Two studies were conducted to investigate the growth and activity of the fungus, Duddingtonia flagrans, within cattle faecal pats. Artificial faecal pats were constructed with the centre separated from the outer layer by a nylon mesh. Eight treatments were tested, by varying the presence/absence of Cooperia oncophora eggs and fungal spores within each layer. With parasite eggs in the centre layer, a statistically lower recovery of larvae was observed compared to both pats with parasite eggs in the periphery and pats with parasite eggs throughout both layers. Regardless of location within the pat, if co-located with the parasite egg, D. flagrans was found to be effective in trapping developing larvae. The reduction in recovery of larvae from pats with parasite eggs and fungal spores in the centre was found to be significantly higher than when parasite eggs were in the centre and fungal spores in the periphery. In the second study, pats were made up in two treatments: pats containing fungal spores and C. oncophora eggs (fungus) and pats containing C. oncophora eggs (control). The pats were incubated at low or high humidity. Ten pats were used in a cross over where five pats incubated at low humidity for 7 weeks were removed, water added and then incubated at a high humidity for 1 week. Another five pats were incubated at a high humidity for 7 weeks, aerated and incubated at a low humidity for 1 week. There was no apparent growth of fungus in faecal pats incubated at a high humidity and less than 20% of larvae were recovered. The growth of D. flagrans was observed in faecal pats incubated at a low humidity, but a corresponding reduction in the percentage recovery of larvae did not occur, except in week 4. No statistical difference between fungal and control pats was seen in the change over pats. Nematophagous activity was assessed throughout the study and observed in the first 4 weeks within the pats containing fungus.     

Potential application of the entomopathogenic fungus, shape Nomuraea rileyi, for control of the corn earworm, shape Helicoverpa armigera

The entomopathogenic fungus, Nomuraea rileyi, caused 90.5–100% mortality in fourth-instar larvae of the corn earworm, Helicoverpa armigera, when applied at 10⁷ conidia/ml to corn silks, and leaves of soybean, tomato and chrysanthemum. The LT₅₀ was 5.9–6.7 days. The fifth-instar larvae showed a mortality of 94.6% on soil with 20% water content, and 41.7% on 10% water content when the soil surface was sprayed with 10⁸ conidia/ml suspension. Five fungicides, eight insecticides and nine herbicides, which are commonly used in corn fields, were evaluated for inhibition to conidial germination by a paper disk test. Among them, only two fungicides, viz., maneb and propineb, were highly inhibitory, while insecticides and herbicides examined were not inhibitory to the fungus. Field applications of N. rileyi conidial suspension to neonate larvae were found to be as effective as 40.46% carbofuran (EC) at 800-fold dilution in controlling corn earworm based on marketable ears. It is thus suggested that N. rileyi has potential to be a microbial control agent for this insect.     

蝙蝠蛾幼虫肠道中的冬虫夏草菌体研究

西藏林芝地区冬虫夏草天然产区野生虫草蝙蝠蛾幼虫的肠道液pH范围为9.69-10.99,体外在此pH下培养冬虫夏草菌长势较差。同时,在该pH的体外模拟中肠液中,虫菌体也会在极短的时间内消亡,而对自然侵染的蝙蝠蛾幼虫的血淋巴、消化道及其“反吐物”（肠液）进行切片和显微镜检却发现,蝙蝠蛾幼虫消化道、呕吐物中均存在与血淋巴中相同的冬虫夏草菌菌体形态,生存状态良好,正常增殖,表明蝙蝠蛾幼虫肠道的生理状态可以维系并支撑冬虫夏草菌菌体某种形态的存在与生长,并证实冬虫夏草菌由口器及消化道入侵蝙蝠蛾幼虫的可能性;肠道虫菌体与血淋巴虫菌体不一定同时存在,表明冬虫夏草菌对蝙蝠蛾幼虫的侵染可能同时存在表皮侵染和肠道侵染两种途径。本文为冬虫夏草菌对蝙蝠蛾幼虫的侵染途径研究提供更加多样化的信息支持。     

纵坑切梢小蠹携带云南半帚孢研究

云南半帚孢 (Leptogramphyunnanensis)是纵坑切梢小蠹Tomicuspiniperda重要的共生真菌 ,在纵坑切梢小蠹危害寄主树木过程中发挥着重要作用。研究揭示 ,纵坑切梢小蠹主要通过与受到感染云南半帚孢的韧皮组织的接触携带上云南半帚孢的。纵坑切梢小蠹卵、幼虫和蛹对云南半帚孢的带菌率较高 ,均大于 90 % ,而成虫的带菌率较低。纵坑切梢小蠹的体表和体内均携带有云南半帚孢 ,但体表带菌是纵坑切梢小蠹带菌的主要途径。通过对纵坑切梢小蠹成虫头、足、翅和腹部带菌率的研究发现 ,云南半帚孢在纵坑切梢小蠹各部位的分布大体相同 ,揭示纵坑切梢小蠹没有携带云南半帚孢的特化构造或器官。     

First description of the disease by Conidiobolus osmodes on Tipula paludosa larvae with the report of a natural epizootic

A new fungal pathogen of Tipula paludosa (Tipulidae: Diptera) larvae, Conidiobolus osmodes (Ancylistaceae: Entomophthorales), was found during a survey of tipulid larval pathogens in Northumbria and Cumbria in England in 1997-1999. The fungus caused an epizootic in a population at Close House during autumn 1999 and spring 2000 with prevalence rising fourfold reaching about 40% in April 2000. The disease development was presented and the fungus was described from naturally infected larvae and artificial cultures.     

Interaction between the nematophagous fungus Duddingtonia flagrans and infective larvae of Haemonchus contortus (Nematoda: Trichostrongyloidea)

The interaction between Duddingtonia flagrans and infective larvae of Haemonchus contortus was studied in vitro under optical and scanning electron microscopy. Trap formation by the fungus started 9 hours after inoculation and first larvae were found 11 hours after larval inoculation on colonies grown on the surface of dialysis membranes. Scanning electron micrographs were taken 12, 24, 36 and 48 h after larval predation. Details of predation structures and fungus-larvae interaction are described. A mucilaginous substance occurred at the points of adherence of traps to nematode cuticle. Bacteria were also found at some points of interaction between fungus and larval cuticle. Cuticle penetration by fungus hyphae occurred only 48 h after predation.     

Method for quantitative sampling of fungus gnat larvae in soilless growing media

A simple method is described for separating fungus gnat larvae from soilless growing media. Samples are first fractionated by water flotation with an inverted flask procedure and then the sediment is degassed under reduced air pressure and fractionated in magnesium sulfate (MgSO4) solution (density of 1.12 g cm(-3)). Fungus gnat larvae with only a small amount of contaminating debris are recovered from the surface of the MgSO4 solution for immediate counting or for preservation in alcohol. In evaluations of different commercial soilless growing media with a range of components, two repetitions of the water flotation step eliminated 20-40% of the dry weight of samples and virtually all of the perlite from further processing. Repeating both the water and MgSO4 flotations a third time only marginally improved the recovery of larval fungus gnats, Bradysia sp. nr. coprophila, added to pasteurized media. Extraction efficiency differed between instars and, to a lesser extent, between different types of media. Across three commercial soilless media tested, recovery was 24-33% for first, 68-85% for second, 85-95% for third, and 98-100% for fourth instars. Within combinations of media and instar, recovery was consistent. With this method, a 400-cm3 sample can be processed and be ready for counting in 1-1.5 h; samples can also be processed in batches or in assembly-line manner to process many samples per day. The method may also prove useful for quantitative recovery of shore fly larvae, thrips pupae, and other arthropods from soilless growing media.     

Insecticidal and immunosuppressive effect of ascomycete Cordyceps militaris on the larvae of the Colorado potato beetle Leptinotarsa decemlineata

The immunosuppressive and insecticidal activity of culture of the entomopathogenic fungus Cordyceps militaris on the larvae of the Colorado potato beetle Leptinotarsa decemlineata has been established for the first time. It was found that the peroral effect of the fungal culture resulted in dose-dependent decrease in survival, delayed in development time and molting, decreases in the total hemocyt counts, increased activity of phenoloxidases in the hemolymph, and reduced activity of the enzyme in the cuticle, as well as increased sensitivity of larvae to the fungus Beauveria bassiana at the level of the synergistic effect.     

Effectiveness of Bacillus thuringiensis-transgenic chickpeas and the entomopathogenic fungus Metarhizium anisopliae in controlling Helicoverpa armigera (Lepidoptera: Noctuidae)

The use of genetically modified (Bt) crops expressing lepidopteran-specific Cry proteins derived from the soil bacterium Bacillus thuringiensis is an effective method to control the polyphagous pest Helicoverpa armigera. As H. armigera potentially develops resistance to Cry proteins, Bt crops should be regarded as one tool in integrated pest management. Therefore, they should be compatible with biological control. Bioassays were conducted to understand the interactions between a Cry2Aa-expressing chickpea line, either a susceptible or a Cry2A-resistant H. armigera strain, and the entomopathogenic fungus Metarhizium anisopliae. In a first concentration-response assay, Cry2A-resistant larvae were more tolerant of M. anisopliae than susceptible larvae, while in a second bioassay, the fungus caused similar mortalities in the two strains fed control chickpea leaves. Thus, resistance to Cry2A did not cause any fitness costs that became visible as increased susceptibility to the fungus. On Bt chickpea leaves, susceptible H. armigera larvae were more sensitive to M. anisopliae than on control leaves. It appeared that sublethal damage induced by the B. thuringiensis toxin enhanced the effectiveness of M. anisopliae. For Cry2A-resistant larvae, the mortalities caused by the fungus were similar when they were fed either food source. To examine which strain would be more likely to be exposed to the fungus, their movements on control and Bt chickpea plants were compared. Movement did not appear to differ among larvae on Bt or conventional chickpeas, as indicated by the number of leaflets damaged per leaf. The findings suggest that Bt chickpeas and M. anisopliae are compatible to control H. armigera.     

Physiological responses of apple fruits to oxygen concentrations

In experiments applying water regimes ranging from one eighth to twice the recorded average rainfall to six soils (two light sands and four silty clay loams) consistent positive correlations were found between rainfall and (a) the growth of foliage and roots of spring barley and spring oats, (b) the number of larvae which invaded the root system, (c) the number of immature females in July, and (d) the incidence of the fungus Verticillium chlamydosporium, an egg parasite of H. avenae. Final cyst numbers were sometimes lower than the number of immature females, probably because the latter were destroyed by the ‘Entomophthora-like’ fungus (Kerry & Crump 1977). Final populations of cysts and eggs were not always proportional to the number of larvae in root systems (even when the proportion of males was constant) but appeared more likely to be so in light sandy soils.     

Formulation and application of the entomopathogenic fungus: Zoophthora radicans (Brefeld) Batko (Zygomycetes: Entomophthorales)

Aims: To isolate and formulate a native strain of Zoophthora radicans naturally infecting larvae of diamondback moth, Plutella xylostella, existing in South Australia and to provide evidence that formulation of the fungus is effective against P. xylostella larvae, and therefore, it could be used as a tool in pest management of this insect. Methods and Results: Dose–response bioassays using formulated and unformulated forms of the fungus strain were carried out against third instar larvae of P. xylostella. Results obtained have indicated a significant increase in the larval mortality when higher concentrations of a formulated form of the fungus strain were applied compared to the treatments with the unformulated form (85·0 vs 57·5% of larval mortality, respectively, at the top concentration of 10⁷ conidia/ml). The median lethal concentration (LC50) for a formulated form was 100 times less than that of the unformulated form when they were applied against the third instar larvae of P. xylostella. In addition, the formulation used in the present bioassays has preserved the viability of introduced fungus conidia for longer time in comparison with the unformulated conidia. Conclusions: The effective application of a formulated fungus strain against P. xylostella larvae constitutes the first step towards its use in pest management of this insect. Significance and Impact of the Study: The formulated fungus in inverted emulsion could be used as an alternative tool to insecticides in pest management of P. xylostella larvae because of the development of resistance to insecticides in the treated larvae.     

Fungal infection dynamics in response to temperature in the lepidopteran insect Galleria mellonella

This study examines how the dynamics of fungus–insect interactions can be modulated by temperature. The wax moth, Galleria mellonella, is a well‐studied and important model insect whose larvae in the wild develop optimally at around 34 °C in beehives. However, surprisingly little research on wax moths has been conducted at relevant temperatures. In this study, the entomopathogenic fungus Metarhizium robertsii inflicted rapid and substantial mortality on wax moth larvae maintained at a constant temperature of 24 °C, but at 34 °C a 10 fold higher dose was required to achieve an equivalent mortality. The cooler temperature favored fungal pathogenicity, with condial adhesion to the cuticle, germination and hemocoel invasion all significantly enhanced at 24 °C, compared with 34 °C. The wax moth larvae immune responses altered with the temperature, and with the infective dose of the fungus. Enzyme‐based immune defenses (lysozyme and phenoloxidase) exhibited enhanced activity at the warmer temperature. A dramatic upregulation in the basal expression of galiomicin and gallerimycin was triggered by cooling, and this was augmented in the presence of the fungus. Profiling of the predominant insect epicuticular fatty acids revealed a 4–7 fold increase in palmetic, oleic and linoleic acids in larvae maintained at 24 °C compared with those at 34 °C, but these failed to exert fungistatic effects on topically applied fungus. This study demonstrates the importance of choosing environmental conditions relevant to the habitat of the insect host when determining the dynamics and outcome of insect/fungus interactions, and has particular significance for the application of entomopathogens as biocontrol agents.     

A new fungus disease of the white shrimp Penaeus setiferus

A primary mycosis of larvae of the white shrimp, Penaeus setiferus, is described. The disease first became apparent in larvae in the second protozoeal stage and disappeared as the shrimp reached the first mysis stage. Affected shrimp became immobilized by near complete tissue destruction and replacement by the expanding mycelium. The fungus was found to be Lagenidium sp. and was infective to larval brown shrimp, Penaeus aztecus.     

稻纵卷叶螟根虫瘟霉的分离鉴定及其流行病研究

在广东省发现一种新的侵染稻纵卷叶螟幼虫的昆虫病原真菌,经鉴定该病原真菌为根虫瘟霉Zoophthora radicans,这是中国首次报道该菌侵染稻纵卷叶螟。在室内进行的温度和光周期对该菌生长的影响实验表明,该菌在15－25℃均可生长,最适生长温度为25℃;光周期对菌落生长影响不显著。根虫瘟霉主要侵染稻纵卷叶螟3－5龄幼虫,对3－5龄幼虫的侵染率分别为2.71%、24.32%和72.97%。在10－11月,根虫瘟霉可持续引发稻纵卷叶螟幼虫高强度流行病,侵染率高达95%。该菌以休眠孢子越冬,成为次年稻纵卷叶螟幼虫流行病的初侵染源。因此,根虫瘟霉是稻纵卷叶螟幼虫一种有效的自然控制因子。     

Food preference of the rove beetle, Atheta coriaria Kraatz （Coleoptera： Staphylinidae） under laboratory conditions

A study, involving laboratory choice tests, was conducted to determine the feeding behavior, based on food preference, of the adult and larval stage of the rove beetle, Atheta coriaria Kraatz when presented with both fresh moistened oatmeal and second instar fungus gnat, Bradysia sp. nr. coprophila （Lintner） larvae in Petri dishes. Rove beetles used in this study came from a laboratory-reared colony. A rating scale from 1 to 5, based on percent missing （1 = 0 to 10%, 2 = 11 to 30%, 3 = 31 to 50%, 4 = 51 to 75%, and 5 = 76 to 100%）, was used to objectively assess the amount of oatmeal and number of fungus gnat larvae consumed by each rove beetle adult and larva. In all the choice tests, A. coriaria adults and larvae preferred to feed on fungus gnat larvae （78% and 69%, respectively） significantly more so than oatmeal （9% and 5%, respectively） based on the amount of oatmeal and number of fungus gnat larvae consumed after 4 and 6 hours. There were relatively minimal differences in the amount of food consumed for both adults and larvae after 4 and 6 hours. The results of this study indicate that oatmeal may be an inexpensive supplemental food source, during the rearing process, which will not inhibit the effectiveness of rove beetles to control fungus gnat larvae when released into greenhouses.     

Patterns of functional enzyme activity in fungus farming ambrosia beetles

ABSTRACT: INTRODUCTION: In wood-dwelling fungus-farming weevils, the so-called ambrosia beetles, wood in the excavated tunnels is used as a medium for cultivating fungi by the combined action of digging larvae (which create more space for the fungi to grow) and of adults sowing and pruning the fungus. The beetles are obligately dependent on the fungus that provides essential vitamins, amino acids and sterols. However, to what extent microbial enzymes support fungus farming in ambrosia beetles is unknown. Here we measure (i) 13 plant cell-wall degrading enzymes in the fungus garden microbial consortium of the ambrosia beetle Xyleborinus saxesenii, including its primary fungal symbionts, in three compartments of laboratory maintained nests, at different time points after gallery foundation and (ii) four specific enzymes that may be either insect or microbially derived in X. saxesenii adult and larval individuals. RESULTS: We discovered that the activity of cellulases in ambrosia fungus gardens is relatively small compared to the activities of other cellulolytic enzymes. Enzyme activity in all compartments of the garden was mainly directed towards hemicellulose carbohydrates such as xylan, glucomannan and callose. Hemicellulolytic enzyme activity within the brood chamber increased with gallery age, whereas irrespective of the age of the gallery, the highest overall enzyme activity were detected in the gallery dump material expelled by the beetles. Interestingly endo-beta-1,3(4)-glucanase activity capable of callose degradation was identified in whole-body extracts of both larvae and adult X. saxesenii, whereas endo-beta-1,4-xylanase activity was exclusively detected in larvae. CONCLUSION: Similar to closely related fungi associated with bark beetles in phloem, the microbial symbionts of ambrosia beetles do not degrade cellulose. Instead, their enzyme activity is directed mainly towards comparatively more easily accessible hemicellulose components of the ray-parenchyma cells in the wood xylem. Furthermore, the detection of xylanolytic enzymes exclusively in larvae and not in adults indicates that larvae (pre-) digest plant cell wall structures exclusively in larvae (which feed on fungus colonized wood) and not in adults (which feed only on fungi). This implies that in X. saxesenii and likely also in many other ambrosia beetles, adults and larvae do not compete for the same food within their nests - in contrast, larvae increase colony fitness by facilitating enzymatic wood degradation and fungus cultivation.     

A mycosis caused by Lagenidium sp. in laboratory-reared larvae of the Dungeness crab,Cancer magister,and possible chemical treatments

A mycosis in larvae of the Dungeness crab, Cancer magister, was observed about 48 hr after they had molted to second-stage zoeae in the laboratory during a chronic bioassay. The fungus was of the genus Lagenidium and caused about 40% mortality of larvae before the test was terminated. Hyphal development and subsequent sporulation of the fungus was observed over a range of 0–32‰ salinity, with an optimum around 16‰. Bioassays of eight fungicides and the herbicide trifluralin, using the larvae and fungus in separate tests, were performed to explore means of chemical treatment. Trifluralin was the most satisfactory of the chemicals screened, with captan, Cu²⁺, and benomyl also giving good results for certain treatment intervals of up to 96 hr. Malachite green was toxic to larvae at concentrations inhibiting the fungus.     

Interaction between the black yeast Aureobasidium pullulans and the gall midge Lasioptera ephedricola in gall formation on the desert shrub Ephedra trifurca

Galls produced by the cecidomynd Lastoptera ephedncola on Ephedia trifurca always have a black ring associated with them while galls produced by the congener L ephedrae never do Black ring material after microscopic examination and culture proved to be Aureobasidium pullulans In addition to lacking black ring material neither L ephedrae galls nor healthy stems consistently yielded Aureobasidium on culture Gall and larva size measurements indicated that continued larval presence is not necessary for gall development, suggesting fungus initiated gall formation However inoculation of healthy stems with Aureobasidium caused lesions hut not galls The mycelium m galls did not appear grazed and neither larvae nor pupae contained Aureobasidium propagules suggesting that larvae do not feed directly on fungi These data also suggest that there is no trans-pupal passage of fungus from larvae or pupae to adults Newly emerged females do not carry fungal propagules suggesting that thcy are not inoculated upon exiting the gall Gall position leaf culture and stem culture data suggest that the fungus is picked up from leaves prior to oviposition     

First steps towards biological control of the pear gall midge (Contarinia pyrivora) with the insect pathogenic fungus Metarhizium brunneum

Gall midges are important pests in many crops. In fruit, they are difficult to control due to their life cycle, which takes place partially within the fruit. Here, we provide the first successful laboratory experiment to infect pear gall midge (Contarinia pyrivora) with the insect pathogenic fungus Metarhizium brunneum. We developed a procedure for sampling larvae, maintaining them in the laboratory and subjecting them to the fungus. We demonstrated that dipping larvae in a fungus suspension or adding a fungus suspension to the soil result in significant fungus induced mortality of the pear gall midge. An immune response in treated larvae was recorded proving that there was a real pathogenesis. Finally, we discuss next steps and a strategy for field experiments.     

Olfactory and gustatory behaviour by larvae of shape Lobesia botrana in response to shape Botrytis cinerea

In vineyards, larvae of Lobesia botrana (Denis and Schiffermüller) (Lepidoptera: Tortricidae) and Botrytis cinerea (Persoon: Fries) often occur together. This study was carried out to establish whether first instar larvae are attracted by the fungus. Olfactory and gustatory responses of larvae to the fungus were investigated on grape berry clusters (Vitis vinifera) and in two types of olfactometer. In clusters infected partly by B. cinerea, 82% of first instar larvae settled where berries had been infected. In the olfactometers, first instar larvae detected and discriminated between two tested foods. They significantly preferred synthetic media or grape berries (cv., 'Alphonse Lavallée' or 'Cabernet Sauvignon') infected with B. cinerea to non-infected controls. The olfactory response led to 62.2% to 72.6% of the first instar larvae attracted by the fungus and the association of olfactory with gustatory responses resulted in similar rates (64.1% to 81.6%). So, the larvae were most attracted by synthetic media or grape berries infected by the fungus as compared to the controls. Olfaction appears to be the main sense involved in this attraction process.