Control of Brennandania lambi (Acari: Pygmephoroidea) by freezing: evaluation of its efficacy and effects on mushroom growth and yield

Laboratory and field studies were conducted to evaluate freezing as a control measure against Brennandania lambi (Krczal) which infests cultivated mushrooms (Agaricus bisporus) in Shanghai primarily through contaminated spawn. Laboratory experiments showed that exposure of contaminated spawn at -10° C for 24 h killed all stages of B. lambi. These mites probably died due to the freezing of body tissues during sustained exposure at -10° C for 24 h. because the supercooling points for the egg, active larva, quiescent larva, non-gravid adult and gravid adult of B. lambi were respectively -11.34, -10.96, -11.43, -7.65 and -11.20° C, whereas the freezing points were respectively -6.68, -6.84. -6.56, -3.96 and -6.75 °C. Semi-field experiments showed that compost inoculated with B. lambi-infested spawn that had been exposed at -10 °C for 24 h had no mite infestation during spawn running and thus mycelium growth was normal. Laboratory and field experiments during 1989 to spring 1990 showed that freezing spawn had no effect on mushroom yield. Further field experiments in two farms during fall 1990 showed no effect of freezing spawn on yield in one farm and increased yield in the other farm. A field experiment during 1991 to 1992 also indicated that freezing spawn -10 °C for 24 h to 34 h had no effect on mushroom yield.     

Host feeding,damage and control of the mushroom pest,Brennandania lambi (Acari: Pygmephoroidea) in China

The pygmephoroid mite, Brennandania lambi (Krczal), is the most serious mite pest of mushroom production in Shanghai. China. This mite could not develop and reproduce on the mycelia of Lentinus edodes, Flammulina velutipes, Pleurotus ostreatus or Pleutotus sajor-caju, but 12–20% of the females survived 15 to 31 days on these hosts, whereas all mites died after 8 days in absence of food. When fed the mycelia of Auricularia polytricha, B. lambi adults could become gravid and reproduce but active larvae failed to develop to the next stage. B. lambi developed and reproduced on the mycelia of Auricularia auricula, Hericium erinaceus, Tremella fuciformis and Agaricus bisporus. Mobile stages of B. lambi damage A. bisporus by feeding on its mycelia. Field surveys of mite damage during 1983–1989 in the suburbs of Shanghai revealed that contaminated spawn was the major source of the mite problem and losses of the crop averaged between 10% and 20%. Experiments on the effects of temperature on mite survival indicate that exposure of mites at 50° C for 1 hour or-10°C for 24 hours killed all stages of B. lambi. Thus, heating treatment during well-executed phase II composting and freezing of mushroom spawn at-10° C for 24 hours should eliminate or at least reduce the damage to mushrooms by this pest.     

Phoretic dispersal ofBrennandania lambi (Kcrzal) (Acari: Tarsonemida: Pygmephoridae) by mushroom flies (Diptera: Sciaridae and Phoridae) in New South Wales,Australia

The phoridMegaselia halterata (Wood) was found to carry significantly moreBrennandania lambi (Kerzal) than the sciaridLycoriella mali (Fitch) in samples collected from six mushroom farms.B. lambi was attached to both the phorids and mainly between the procoxae and mesosternum (57&) and between metacoxae and the first abdominal sternite (36%).B. lambi detached fromM. halterata only in the presence ofAgaricus mycelium. Evidence for dispersal ofB. lambi byL. mali andM. halterata is presented and the role of phoresy in the dispersal ofB. lambi is discussed.     

Attraction of female fungus gnats,Lycoriella ingenua,to mushroom‐growing substrates and the green mold Trichoderma aggressivum

To evaluate the attractiveness of several mushroom‐growing substrates to the female mushroom fly Lycoriella ingenua (Dufour) (Diptera: Sciaridae), a pest of the cultivated white button mushroom, Agaricus bisporus (JE Lange) Emil J Imbach (Agaricales), we developed a two‐choice, static‐flow olfactometer. Behavioral assays using this olfactometer indicated that mushroom compost with A. bisporus mycelia growing in it was not more attractive than compost lacking growing mycelia. We also found that female flies were more attracted to compost lacking A. bisporus mycelia than to the actual commodity, the white button mushroom fruiting bodies. Flies were not, however, attracted to sterilized compost, suggesting the attraction is due to volatiles produced by microbial metabolism in the compost. We also found that female L. ingenua flies were attracted to the mycoparasitic green mold Trichoderma aggressivum Samuels & W Gams (Hypocreales). Flies preferred mushroom compost that had T. aggressivum growing in it over compost lacking T. aggressivum, providing an experimental outcome consistent with the anecdotal belief that L. ingenua flies are vectors of T. aggressivum spores that can infest mushroom‐growing houses.     

Temperature,time, and the influence of volatiles on phialospore germination in Verticillium malthousei Ware

Phialospores of Verticillium malthousei Ware were atomized onto acclimatized water agar and incubated for 3, 6, 9, 12, and 24 hr at 12 to 36 °C at 6 °C intervals. Germination occurred at all temperatures exclusive of 36 °C with maximum germination (90–98 %) occurring in 24 hr at 12 °C, 12 hr at 18 °C, 9 hr at 24° and 30 °C. Volatiles from: 1) horse manure compost colonized by Agaricus bisporus; 2) mycelium impregnated casing (soil); or 3) casing supporting mature and immature mushrooms had no statistically significant effect on spore germination of V. malthousei when measured after 12 hr at 24 °C. However, a tendency towards inhibition after 6 and 12 hr at 24° and 12 °C, respectively, suggests the inhibition is temperature and time dependent. This dependency was noted with two substrates, colonized compost and casing which supported sporocarps.The statistical and programming assistance of Dr. J. A. Ayers, Department of Plant Pathology, Dr. R. Craig, Department of Horticulture, and Ms. Isabel M. Hoover, Agricultural Statistic Laboratory, The Pennsylvania State University is gratefully acknowledged.Contribution No. 759 from the Department of Plant Pathology, The Pennsylvania Agriculture Experiment Station. Authorized for publication as Journal Series Paper No. 455.0 on October 8, 1973.     

Abundance and distribution of <Emphasis Type="Italic">Microdispus lambi</Emphasis> (Acari: Microdispidae) in Spanish mushroom crops

The myceliophagous mite Microdispus lambi has become a veritable plague since 1996, when it was first observed in Spanish mushroom crops, and is now causing substantial economic losses, particulary in spring and summer. This study looks at seasonal variation of the pest, its distribution on commercial farms and the population development during the crop cycle of the common white mushroom, Agaricus bisporus. Over a period of 18 months, 24 consecutive mushroom crop cycles were monitored and a total of 24 spawn and 960 substrate samples were analysed. We found that it is usually the substrates in the growing rooms that are infested, most commonly the compost. In many cases, the pest can be detected when the first ‘flush’—i.e., mushroom growth surge, with weekly periodicity—is harvested, although damage does not become evident until the third flush. Mites were detected at the back of the mushroom growing room and, to a lesser extent, near the access door.     

Life history of Euseius scutalis feeding on citrus red mite Panonychus citri at various temperatures

The aim of this study was todetermine the biology and reproductivepotential of Euseius scutalis(Athias-Henriot) (Acari: Phytoseiidae) atvarious temperatures. These data are of valuein relation to mass rearing and the developmentof population dynamics models. The developmenttime, survival and fecundity of E.scutalis were determined at 20, 25 and30 ± 1 °C, 65 ± 10% RH and 16:8photoperiod. Total development times of E.scutalis were 6.7, 4.9 and 4.2 days at 20, 25and 30 ± 1 °C, respectively, using adiet of all life stages of the spider mite Panonychus citri (McGregor) (Acari:Tetranychidae). In general, preoviposition andpostoviposition periods of E. scutaliswere shortened as temperature increased, butthe oviposition period was longer at 25 °C than at 20 and 30 °C. Theshortest survival time of E. scutalis, at30 °C, was 10.1 days, followed by 23.7days and 28.6 days at 20 and 25 °C,respectively. Mated females laid on average1.1, 1.4 and 1.7 eggs per female per day and21.5, 39.7 and 17.1 eggs over their entire lifetime at 20, 25 and 30 °C, respectively.The sex ratios of E. scutalis were2.11/1, 2.24/1 and 2.11/1 female/male at 20, 25and 30 °C, respectively. The intrinsicrate of natural increase (r _m) increasedwith rising temperatures from 0.166 at 20 °C to 0.295 females/female/day at 30 °C. The net reproductive rate (R ₀)was highest at 25 °C (26.03females/female) and lowest at 30 °C(12.95 females/female). Mean generation time(T ₀) was longest at 25 °C (17.50days) and shortest (9.53 days) at 30 °C.     

Comparison of characterization and microbial communities in rice straw- and wheat straw-based compost for <Emphasis Type="Italic">Agaricus bisporus</Emphasis> production

Rice straw (RS) is an important raw material for the preparation of Agaricus bisporus compost in China. In this study, the characterization of composting process from RS and wheat straw (WS) was compared for mushroom production. The results showed that the temperature in RS compost increased rapidly compared with WS compost, and the carbon (C)/nitrogen (N) ratio decreased quickly. The microbial changes during the Phase I and Phase II composting process were monitored using denaturing gradient gel electrophoresis (DGGE) and phospholipid fatty acid (PLFA) analysis. Bacteria were the dominant species during the process of composting and the bacterial community structure dramatically changed during heap composting according to the DGGE results. The bacterial community diversity of RS compost was abundant compared with WS compost at stages 4–5, but no distinct difference was observed after the controlled tunnel Phase II process. The total amount of PLFAs of RS compost, as an indicator of microbial biomass, was higher than that of WS. Clustering by DGGE and principal component analysis of the PLFA compositions revealed that there were differences in both the microbial population and community structure between RS- and WS-based composts. Our data indicated that composting of RS resulted in improved degradation and assimilation of breakdown products by A. bisporus, and suggested that the RS compost was effective for sustaining A. bisporus mushroom growth as well as conventional WS compost.     

Welche Möglichkeiten eröffnet der viersporige Champignon „Agaricus bitorquis (Quél.) Sacc.”" dem Züchter?

Zusammenfassung A. bitorquis wurde erst im Jahre 1968 in Kultur genommen. Er unterscheidet sich von dem bisher ausschließlich kultivierten Champignon A. bisporus durch eine Reihe von Eigenschaften. Die Temperaturansprüche liegen etwa 5° C höher. Die Fruchtkörper (weiß, glatt) sind kräftiger als die Sporophoren der weißen ungeschuppten Sorten von A. bisporus. Besonders wertvolle Eigenschaften, die A. bitorquis mitbringt, sind die Virusresistenz, Druckunempfindlichkeit, leichte Pflückbarkeit und längere Lagerfähigkeit. Die Basidie schnürt 4 statt 2 Sporen ab. Demzufolge sind Einsporkulturen steril und ist systematisches Kreuzen eine züchterisch anwendbare Methode.Da die Hyphen keine Schnallen bilden, ist eine mikroskopische Unterscheidung von monokaryotischem und dikaryotischem Mycel nicht möglich. Wie die Versuche zeigten, kann die Compatibilität der Einsporkulturen jedoch am Wachstumsverhalten des Mycels auf Biomalz-Agar erkannt werden. Wo ein heterokaryotisches Mycelium zustande kommt, kann belagartiges, langsam wachsendes Mycel in zunächst flauschiges, dann fädig schnellwachsendes Mycel übergehen. Bei genügend Luftzufuhr können sich Mycelverdichtungen bilden.Einige Paarungen von Einsporkulturen verschiedener Herkunft brachten sehr gut gesichert höhere Erträge als die elterlichen Wildtypen, während andere Kreuzungen zweier Einsporkulturen den Eltern im Ertrag sehr gut gesichert unterlegen waren. Die Kombination der elterlichen Wildtypen unterschied sich im Ertrag kaum von den Wildtypen selbst. Im Ertragsverlauf gab es im allgemeinen starke Unterschiede.Eine große Variabilität zeigten die Stämme auch in der Form und Farbe der Fruchtkörper, ihrer Verteilung auf dem Beet sowie in anderen Eigenschaften wie der Neigung des Mycels, in die Deckerde zu wachsen. Die Ergebnisse werden diskutiert.

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What potentialities does the four-spored mushroom Agaricus bitorquis (Quél.) Sacc. offer to the breeder?

Summary A. bitorquis was first taken into cultivation in 1968. It differs from A.bisporus, the only mushroom cultivated previously, in a range of properties. The claims for temperature are about 5° C higher. The fruitbodies (white smooth) are more vigorous than the sporophores of the white, scale-less strains of A.bisporus. Especially valuable characteristics which A. bitorquis brings are virus resistance, resistance to pressure, easy pickability and longer shelflife. The basidia have 4 instead of 2 spores. Consequently monosporecultures are infertile and systematic crossbreeding is a suitable breeding method.Because the hyphae do not form clamp connections, it is not possible to distinguish microscopically monocaryotic and dicaryotic mycelium. As the trials have shown, however, the compatibility of the monospore cultures can be recognized by the manner of mycelium growth on biomalt-agar. Where heterocaryotic mycelium has arisen matted, slow growing mycelium can turn into fluffy, and later on stringy fast-growing mycelium. With enough ventilation condensations of mycelium can be formed. Some combinations of monospore-cultures of different origin showed very significantly higher yields than the parental wild types, whereas other combinations of two monospore cultures were very significantly lower in yield than the parents. The combination of parental wildtypes scarcely differed in yield from the wildtype self. Regarding the course of the yield there were big differences in general.The strains also showed great variability in the shape and colour of the fruitbodies, their distribution on the bed and in other properties, such as the propensity of the mycelium to grow into the casing layer. The results are discussed.

     

Effect of different Agaricus species on the development of the mushroom sciarid fly Lycoriella ingenua

Isolates from eight species of Agaricus were investigated in laboratory experiments for their effect on the development of the mushroom sciarid fly, Lycoriella ingenua (Dufour) (Diptera: Sciaridae), which is an important pest of the white mushroom Agaricus bisporus (Lange) Imbach (Agaricaceae). The population levels of L. ingenua developing in compost inoculated with Agaricus mycelium varied with the Agaricus isolate used, with some isolates causing high levels of inhibition. The development of L. ingenua populations and the survival of larval instars were inversely proportional to the amount of Agaricus inoculum applied. There was also a negative relationship between L. ingenua survival and the extension rate of the Agaricus isolate in compost. The results suggest that inhibition of L. ingenua population development by Agaricus is linked to the rate at which compost is colonized by fungal mycelium. Therefore, on mushroom farms, sciarid fly control should focus on protection of the compost before it has become colonized by mycelium, as this is when it is most vulnerable to the pest.     

Stimulation of environmentally controlled mushroom composting by polysaccharidases

Polysaccharidases adsorbed on commercial amylodextrins were added to environmentally controlled composts of straw plus poultry manure. After 5 days of composting at 48°C, microbial enzyme activities and numbers of bacteria were higher in the treated compost than in the control. During the next phase at 80°C, between days 5 and 6, more C and N were solubilized in the treated compost. After introducing a microbial inoculum on day 6, and maintaining the substrate at 48°C, colonization by bacteria was faster in the treated compost and consequently, more fibre was degraded. Differences between composts in yields of Agaricus bisporus after 5 weeks of cropping were not significant (P=0.05).The authors are with INRA, Station de Recherches sur les Champignons, BP 81, 33883 Villenave d'Ornon, France     

DGGE and T-RFLP Analysis of Bacterial Succession during Mushroom Compost Production and Sequence-aided T-RFLP Profile of Mature Compost

The amount of button mushroom (Agaricus bisporus) harvested from compost is largely affected by the microbial processes taking place during composting and the microbes inhabiting the mature compost. In this study, the microbial changes during the stages of this specific composting process were monitored, and the dominant bacteria of the mature compost were identified to reveal the microbiological background of the favorable properties of the heat-treated phase II mushroom compost. 16S ribosomal deoxyribonucleic acid (rDNA)-based denaturing gradient gel electrophoresis (DGGE) and terminal restriction fragment length polymorphism (T-RFLP) molecular fingerprinting methods were used to track the succession of microbial communities in summer and winter composting cycles. DNA from individual DGGE bands were reamplified and subjected to sequence analysis. Principal component analysis of fingerprints of the composting processes showed intensive changes in bacterial community during the 22-day procedure. Peak temperature samples grouped together and were dominated by Thermus thermophilus. Mature compost patterns were almost identical by both methods (DGGE, T-RFLP). To get an in-depth analysis of the mature compost bacterial community, the sequence data from cultivation of the bacteria and cloning of environmental 16S rDNA were uniquely coupled with the output of the environmental T-RFLP fingerprints (sequence-aided T-RFLP). This method revealed the dominance of a supposedly cellulose-degrading consortium composed of phylotypes related to Pseudoxanthomonas, Thermobifida, and Thermomonospora.     

Temperature influence on cohort parameters and demographic characteristics of the two cowpea coreids Clavigralla tomentosicollis and C. shadabi

Age-specific life tables of two important pests of cowpea, Vigna unguiculata (L.) Walp., the pod sucking bugs Clavigralla tomentosicollis Stål and C. shadabi Dolling (Heteroptera: Coreidae), were obtained from observations carried out at different temperatures. A biophysical model was found satisfactory to describe the temperature-response of developmental and mortality rates of egg and nymphal stages, with a peak developmental rate around 34°C in both species. The variability in development times was small and the experimental data did not permit any conclusion with regard to the Erlang probability density function. Survival of eggs and nymphs remained high between 20° and 30°C for both species. At temperatures above 34°C, C. tomentosicollis survivorship and fecundity was higher than that of C. shadabi, which in turn laid more eggs at temperatures between 20° and 30°C. Maximum fecundity is estimated to be at 29°C for C. tomentosicollis (99 eggs/female) and 26°C for C. shadabi (261 eggs/female). At 30°C, the intrinsic rate of increase reached a maximum in both species, 0.152 per day for C. tomentosicollis and 0.145 per day for C. shadabi, and remained high for C. tomentosicollis until 36°C. C. tomentosicollis performed significantly better on pigeonpea, Cajanus cajan Millsp., than on cowpea at higher temperatures.     

Combined Effects of Seawater Temperature and Salinity on Development of the Larvae of the Rhizocephalan Peltogaster reticulatus (Crustacea: Cirripedia)

The effects of seawater temperature (12, 16, 20, 22, and 25°C) and salinity (of 8 to 34) in different combinations on the larvae of the rhizocephalan Peltogaster reticulatus (Crustacea: Cirripedia), a parasite of the hermit crab Pagurus proximus, were examined. The development of P. reticulatus is comprised of five naupliar stages and one cypris stage. Nauplii have a specific structure, the flotation collar encircling the dorsal side of the larval body. Larvae lack the pigmented nauplius eye, and they show no positive phototaxis. Successful naupliar development occurred in temperature and salinity ranges of 16–25°C and 20 to 34, respectively; but all nauplii died at 12°C and 16. The duration of each naupliar stage increased under lowering of the seawater temperature. At 22–25°C and 26–28, the entire development cycle was completed in 72–80 h; and at 16°C and 20 it lasted 153 h. The cypris larvae showed a greater resistance to decreased salinity in comparison with the nauplii. At temperatures of 16–25°C and salinities of 14 to 34, the lifespan of cyprids was 6 to 12 days, and it decreased at increasing temperature.     

Effects of leaf-matter incorporation on Aphelenchoides composticola (Nematoda), mycofloral composition, mushroom compost quality and yield of Agaricus bisporus

Incorporation of dried leaves of Azadirachta indica, Cannabis sativa, Eucalyptus tereticornis and Ricinus communis at 3 kg per 100 kg of dry wheat straw prior to composting had several effects. When compared with controls, treated composts exhibited a higher temperature during composting, a higher nitrogen content and a neutral pH. The treatments resulted in enhanced populations of thermophilic fungi and mesophilic antibiotic-producing fungi, but reduced numbers of mesophilic competitor/pathogenic moulds. Populations of the mycophagous nematode, Aphelenchoides composticola were reduced below economic injury level in dried leaf treated composts. Compost obtained from C. sativa and R. communis treatments were more rapidly colonised by the mushroom mycelium (Agaricus bisporus) than that from any other treatment. When compared with compost treated with carbofuran R. communis, C. sativa and A. indica treatments significantly increased mushroom yield by 19.4, 8.1 and 6.5% and by 108.5, 88.7 and 85.9% when compared with the control. Yield from the E. tereticornis treatment was also higher than the control but lower than that of the nematicide treatment.     

Temperature-induced changes in spider mite fitness: offsetting effects of development time, fecundity, and sex ratio

Temperature affects many life history parameters in poikilotherms. Temperature clearly affects development time and fecundity, which affect the intrinsic rate of increase. In haplodiploid mites, ambient temperature may also affect offspring sex ratio which, in turn, affects intrinsic rate of increase. The combined effect of all these processes determines the fitness of individual females. However, sex ratio also affects mating structure and, potentially, rate of local adaption. We investigated the direct effect of temperature variation on sex ratio, development time, and fecundity in the twospotted spider mite (Tetyranychus urticae), and calculated the effect of their interaction on mite intrinsic rate of increase. We conducted experiments at 2 temperatures and designed the experiment to separate pre-adult and adult sensitivity to temperature variation. Mites were reared from eggs to adult ecdysis at either 22°C or 32°C. Upon emergence as adults, these 2 groups were each split between 22°C and 32°C and allowed to oviposit. Not surprisingly, development from egg to adult was accelerated when mites were exposed to the higher temperature during offspring development, regardless of the temperature experienced by the mother during her development. Fecundity and the proportion of female offspring were affected by temperature only when mothers were exposed during both development and oviposition. About 12 offspring were gained and female bias was increased by 26% when the mother's development occurred at 22°C, whereas oviposition at 22°C added only 6 more offspring and increased female bias by only 7%. There was no correlation between sex ratio and fecundity; both were related to temperature but not to each other. Furthermore, development time, not fecundity or sex ratio, appeared to the main factor affecting the intrinsic rate of increase. Our results support other evidence that sex ratio varies independently of development time and fecundity.     

Evaluation of the behavioural response of the flies Megaselia halterata and Lycoriella castanescens to different mushroom cultivation materials

A static‐air olfactometer was used to investigate the behavioural responses of adult female phorid [Megaselia halterata (Wood) (Diptera: Phoridae)] and sciarid [Lycoriella castanescens (Lengersdorf) (Diptera: Sciaridae)] flies to the commercial white mushroom, Agaricus bisporus (Lange) Imbach, grown on a standard pasteurised composted substrate. The attraction of the flies was measured in relation to four test materials: composted substrate spawned with A. bisporus mycelium for 4 days and 14 days, uncolonised composted substrate, and A. bisporus sporophores. The experiment was done according to a 4 × 4 × 4 Latin cube design, and the results were analysed using a generalised linear model. It was found that both the occasion on which a bioassay was run and the position of the olfactometer within a 4 × 4 array could affect the proportion of the fly population responding to a test material. Megalesia halterata preferred spawned compost to unspawned compost, and the level of response to compost spawned for 14 days was greater than to compost spawned for 4 days. In contrast, L. castanescens were attracted equally to all of the materials tested. Overall, L. castanescens showed a greater level of activity than M. halterata, and was more likely to enter the pitfall traps in the olfactometer. For both M. halterata and L. castanescens, the type of test material affected the numbers of adult flies of the F₁ generation that emerged from it following oviposition. The highest numbers of emerging M. halterata were obtained from a composted substrate spawned for 4 days, and none emerged from the unspawned compost. Emergence of L. castanescens was highest from the uncolonised composted substrate, and there was a negative relationship between emergence and the amount of mycelium in the composted substrate. The results are consistent with the use of volatiles in the detection of oviposition sites by both species; however, further studies of the materials will be necessary to determine precisely which oviposition cues the insects use.     

The effect of inoculation with Selenophoma donacis at different growth stages on spring barley cultivars

A technique used for 3 yr to produce 15 000–20 000 nematode-free adult Megaselia halterata/v/k is described and its potential for future mass-production of nematode-parasitised flies, for use in biological control, is assessed. Gravid female phorids preferred to oviposit in compost in which mushroom mycelium had grown for 7–12 days. At 20 ± 1 °C flies began to emerge 24 days after adults of the previous generation had been released on the compost. By day28, 88% of the total population had emerged. In laboratory experiments using different densities of parental flies, fly yield per female was highest when 200 flies infested each 1 kg of compost. At higher densities, competition between larvae affected survival of larvae and pupae, and probably resulted in the mean egg content of emerging flies being reduced by as much as 16-4%. Theoretically, 250 kg compost should yield 1 150 000 phorids.     

Effects of Caenorhabditis elegans (Nematoda: Rhabditidae) on yield and quality of the cultivated mushroom Agaricus bisporus

Thirteen species of saprobic rhabditid nematodes (11 genera) were identified from samples of compost and casing material collected from mushroom farms in the British Isles. Caenorhabditis elegans, the most frequently found saprobe, was mass-produced monoxenically and its effects on the cultivated mushroom, Agaricus bisporus (strain U3) were studied. C. elegans did not multiply in well-prepared, pasteurised, spawned compost, whereas casing material proved to be a highly suitable environment for its reproduction. An initial casing inoculum of 10⁶ nematodes/crate of compost (7.5 kg), caused a significant reduction in mushroom yield. Losses in total mushroom yields of 11%, 20% and 26% were caused by initial inoculum rates of 10⁶, 10⁷and 2 × 10⁷ nematodes/crate, respectively. Yields were negatively correlated with the initial nematode inoculation level and regression equations were derived. The nematode treatments caused fewer mushrooms to be produced and an absence of the usual distinctive flushing patterns. C. elegans caused considerable deterioration in mushroom quality and characteristic distortion of mushrooms. Individual sporophores were mis-shapen, notched and had brown or violet coloured grills. Up to 3.8%, 6.7% and 10.8% of total weight and 3.5%, 5.4% and 8% of total numbers of mushrooms were distorted at the three highest nematode inoculum rates tested. Weights and numbers of distorted mushrooms were positively correlated with the initial nematode population. C. elegans commonly colonised sporophores.