Phoretic relationship between the myceliophagous mite Microdispus lambi (Acari: Microdispidae) and mushroom flies in Spanish crops

We studied the role played by the phorid Megaselia halterata (Wood) and the sciarid Lycoriella auripila (Winnertz) in the phoretic dispersion of the myceliophagous mite Microdispus lambi (Acari: Pygmephoridae). Twenty‐four crops were monitored during 18 months in commercial mushroom farms in Castilla‐La Mancha (Spain). Adults of both species were collected weekly and the mites they carried were counted and identified. Both phorids (19.6%) and sciarids (4.4%) carried the mite M. lambi. The calculated load of each was 3.4 M. lambi mites per phorid and 1.9 per sciarid. The same percentage of male and female phorid was used as vector, but the load was slightly higher for females (1.86 mites per female compared with1.48 mites per male). A mean of 7.2% of the phorids examined in winter were vectors of M. lambi, while in spring and autumn of the first year the average was more than 22%. The mean load did not vary significantly between seasons. Inside the mushroom farms, less than 10% of a small initial population of phorids carried mites (less than two mites per phorid). As the cycle progressed, more than 35% of a larger population of emerging flies did so (average 3.5 mites per phorid vector). At the end of the growth cycle, the flies may fly off to colonise nearby farms, favouring the propagation of M. lambi from infested to uninfested crops. Megaselia halterata is the principal vector of M. lambi in the mushroom farms of Castilla‐La Mancha due to their high numbers, the high percentage carrying mites and the number of M. lambi they carry.     

Bioassay for evaluating attraction of the phorid fly,Megaselia halterata to compost colonized by the commercial mushroom,Agaricus bisporus and to 1-octen-3-ol and 3-octanone

A bioassay chamber was developed to evaluate the attraction of the phorid fly pest,Megaselia halterata (Wood) (Diptera, Phoridae), to volatiles from mushroom compost colonized by the commercial mushroom,Agaricus bisporus (Fungi, Agaricaceae) and to its volatile constituents, 1-octen-3-ol and 3-octanone. The bioassay chamber consisted of a large round container which was attached, via glass tubes, to three removable sample cups situated below the container. Once a fly had entered a sample cup, the flatly cut glass tubes prevented the flies from readily returning to the release chamber and, in effect, was a pit fall trap which kept the flies in the cups until the flies were counted. Holes in the bottom of the cups and removal of 20 ml of air from the chamber to fill the entrance tubes with volatiles from the cups were necessary for the success of the bioassay. Mated and unmated femaleM. halterata and, to a lesser extent, mated males preferred spawned compost (compost well colonized by fungal mycelia) relative to unspawned compost or blank cups. Unmated males were not attracted to spawned compost. Males and females were not attracted to unspawned compost. No attraction of male or femaleM. halterata to the spawned compost volatiles, 1-octen-3-ol and 3-octanone, could be demonstrated under various experimental conditions. These two compounds seemed to deter females at high concentrations.     

Some observations on a Tylenchid nematode Howardula sp. parasitizing the mushroom phorid Megasalia halterata (Phoridae, Diptera)

Howardula sp. parasitizes the Mushroom phorid fly Megasalia halterata destroying the fat body and follicular membrane of the fly, decreasing copulation and egg output. With increasing hyperinfestation the fly is rendered sterile. Howardula sp. is host density dependent and reaches a maximum incidence in September and October. Under laboratory conditions fly populations were eliminated in three to five generations. The implications for possible biological control of M. halterata are discussed.     

Studies on an overwintering population of the mushroom phorid Megaselia halterata (Diptera: Phoridae) parasitized by Howardula husseyi (Nematoda: Allantonematidae)

An overwintering population of the mushroom phorid fly Megaselia halterata parasitized by Howardula husseyi was studied in an attempt to explain the winter decline in incidence of parasitism that has been observed in flies from mushroom farms. Fly larvae from eggs hatching in November developed into pupae in December and flies emerged in May. No selective mortality of parasitized specimens of larvae, pupae, or flies was observed. Dead parasites were found in only 10% of parasitized flies. The incidence of parasitism in the emerging flies (50%) was five times that of their parental generation and although parasitism significantly delayed fly emergence the delay was only 2–3 days. There was no evidence of winter decline in parasitism; instead there was strong evidence that parasitism enhanced phorid survival through the winter.     

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.     

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.     

Bendiocarb and diflubenzuron as substitute insecticides for endosulfan in commercial mushroom growing

Diflubenzuron and bendiocarb treatments of compost and casing soil at a rate of 1 g a.i./m² each, resulted in comparable or even improved compost and casing soil colonisation over endosulfan treatments (at a rate of 1.5 g a.i./m²). Alternating diflubenzuron/bendiocarb treatments were preferable to the reverse treatments, which tended to diminish total yield of mushrooms significantly by 1.4–3.9 kg/m². This effect was due to the casing soil treatment with diflubenzuron and not due to the compost treatment with bendiocarb after spawning. The effectiveness of these substitutes for endosulfan was tested on five commercial mushroom farms, where a similar or improved control of Megaselia halterata (Diptera: Phoridae) was obtained over control (endosulfan) treatments. If present, Lycoriella auripila (Diptera: Lycoriidae) was very effectively controlled by the substitute insecticides compared with endosulfan. Relatively high numbers of M. halterata were occasionally observed in endosulfan-treated houses, indicating that a certain level of resistance towards this insecticide may already have developed. This assessment of tolerance in M. halterata emphasised the need for substitute insecticides with different modes of action, in addition to environmental reasons. The chemicals should be alternately applied within individual crops to avoid resistance development.     

Substrate dependent larval development and emergence of the mushroom pests Lycoriella auripila and Megaselia halterata

Pasteurized, spawned, full-grown and immediately-cased full-grown compost were simultaneously exposed to natural populations of the mushroom pests Lycoriella auripila (Winnertz) (Diptera: Sciaridae) and Megaselia halterata (Wood) (Diptera: Phoridae). Different numbers of adults emerged from each of these composts. Highest numbers of L. auripila emerged from spawned and pasteurized compost whereas lowest numbers of L. auripila emerged from full-grown compost. the emergence from full-grown compost was delayed, which could be explained by the delayed development of the larvae in this type of compost. High numbers of M. halterata emerged from compost that was completely colonized by the mycelia of the edible white button mushroom Agaricus bisporus (Lange) Imbach. The immediate covering of the compost with a casing layer significantly lowered the numbers of emerging M. halterata flies. Compared with the emergence pattern from full-grown and immediately-cased full-grown compost, adult M. halterata showed a delayed pattern of emergence in spawned compost. Adult M. halterata did not emerge from pasteurized compost. The results of these experiments enabled us to improve the timing of the application of insect pathogenic nematodes in the control of the larvae of both insect pests.     

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.     

Control of the mushroom pests Lycoriella auripila (Diptera: Sciaridae) and Megaselia halterata (Diptera: Phoridae) by Steinernema feltiae (Nematoda: Steinernematidae) in field experiments

The nematode Steinernema feltiae (Nematoda: Steinemematidae) was tested for its ability to control two main mushroom pests i.e. the sciarid Lycoriella auripila (Diptera: Sciaridae) and the phorid Megaselia halterata (Diptera: Phoridae) in growing-rooms filled with spawned compost. A clear difference between female and male sciarid control was observed. A nematode application 1 day after casing preceded by an application 1 day before casing on the compost caused an almost complete control (97%) of the F1-generation of female sciarids. The F2-generation of females was similarly controlled (95%) by an application 7 days after casing. A dosage of 1 × 10⁶nematodes m^-2was found to be equally effective as higher dosages. Diflubenzuron remained active throughout entire the cropping period with high sciarid mortality rates varying from 72% to 99%. Phorid control was variable and seemed to depend on the presence of sciarids. In one occasion the control rate of F2-generation phorid larvae was 75% and was possibly caused by the presence of new infective juvenile nematodes recycled in F2-generation sciarid larvae. Diflubenzuron did not significantly reduce phorid numbers.     

Current status of the management of fall webworm,Hyphantria cunea: Towards the integrated pest management development

The fall‐webworm (FWW), Hyphantria cunea, is a highly polyphagous insect pest that is native to North America and distributed in different countries around the world. To manage this insect pest, various control methods have been independently evaluated in the invaded areas. Some of the control methods have been limited to the laboratory and need further study to verify their effectiveness in the field. On the other hand, currently, integrated pest management (IPM) has become a promising ecofriendly insect pest management option to reduce the adverse effect of insecticides on the environment. The development of an IPM for an insect pest must combine different management options in a compatible and applicable manner. In the native areas of the insect pests, there are some recommended management options. However, to date, there is no IPM for the management of the FWW in the newly invaded areas. Therefore, to develop an IPM for this insect pest, compilation of effective management option information is the first step. Thus, believing in the contribution of an IPM to the established management strategies, the chemical, biological, natural enemy, sex pheromone, and molecular studies regarding this insect were reviewed and potential future research areas were delineated in this review study. Therefore, using the currently existing management options, IPM development for this insect pest should be the subject of future research in the newly invaded areas.     

Susceptibility of mushroom pests to the insect-parasitic nematodes Steinernema feltiae and Heterorhabditis heliothidis

The potential of two species of insect-parasitic rhabditid nematodes (Steinernema feltiae, Heterorhabditis heliothidis) for biological control of mushroom flies was studied in pot trials. Three Diptera that commonly infest mushroom crops were used; the larvae of Megaselia halterata (Phoridae), Heteropeza pygmaea (Cecidomyiidae) and Lycoriella auripila (Sciaridae) were all susceptible to parasitism by both nematode species. Fewer adult phorids and sciarids emerged when compost was nematode-treated and, for L. auripila, the effects of nematode applications at spawning, casing or on both occasions were compared. Casing treatments were more effective than spawning treatments; little extra benefit was gained from applying the nematodes twice. Populations of paedogenetic larvae of H. pygmaea built up rapidly in untreated compost, but were reduced when S. feltiae was applied, and were eradicated by H. heliothidis. Because they can penetrate insect cuticle, as well as natural body openings, Heterorhabditis spp. may be more suitable than Steinernema spp. for the control of mushroom fly larvae.     

Evaluation of a genetically selected strain of Steinernema feltiae against the mushroom sciarid Lycoriella mali

The control potential of a strain (ScP) of Steinernema feltiae genetically selected against the mushroom sciarid Lycoriella solani, was evaluated for the management of L. mali. Trials were conducted at two commercial mushroom farms with high and low levels of fly infestation. The efficacy of the ScP strain was compared with the SN strain of S. feltiae and the chitin synthesis inhibitor, diflubenzuron. At low densities of L. mali, the two strains did not differ in efficacy and caused 85–94% reduction in fly populations. At high fly densities with a mixed infestation of the phorid fly, Megaselia halterata, the ScP stain caused 56–83% reduction in L. mali populations whereas the SN strain caused 51–73% reduction. Two doses of the improved strain (0.5 times 10⁶ and 1.0 times 10⁶ infective juveniles per m² cropping area) did not differ in efficacy from diflubenzuron which caused 80% reduction in L. mali populations. The lower dose (0.5 times 10⁶) of the SN strain was less effective than diflubenzuron. The ScP strain had a major advantage over the SN strain in persistence in casing material. Nematodes had no significant effect on mushroom yields.     

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.     

Interrelation of mating,flight, and fecundity in navel orangeworm females

The navel orangeworm, Amyelois transitella (Walker) (Lepidoptera: Pyralidae, Phycitini), is an economically important pest of nut crops in California, USA. Improved management will require better understanding of insect dispersal, particularly relative to when mating occurs. A previous study demonstrated a more robust laboratory flight capacity compared to other orchard moth pests, but it was unclear how mating affects dispersal, and how dispersal affects fecundity. In this study, 1‐ and 2‐day‐old females were allowed to fly overnight on a flight mill either before or after mating, respectively, and were then allowed to oviposit. Data on fecundity were compared between treatments to minimally handled or tethered‐only control females. Females that mated before flight flew longer and covered a greater distance than those flying prior to mating. However, timing of flight relative to mating did not affect fecundity, nor did any measure of flight performance. There was no effect on fecundity when females were forced to fly for designated durations from 3 min to 2 h. Together, our data revealed no obvious trade‐off between flight activity and reproductive output. Distances measured on the flight mills (mean ca. 15 km for mated females) may overestimate net displacement in the field where flight tracks are often meandering. The results suggest that most females mate and oviposit in or near their natal habitat, but that some may disperse potentially long distances to oviposit elsewhere.     

Dispersal capacity of Monochamus galloprovincialis,the European vector of the pine wood nematode,on flight mills

The pine wood nematode (Bursaphelenchus xylophilus), which causes the symptoms of pine wilt disease, is recognized worldwide as a major forest pest. It was introduced into Portugal in 1999. It is transmitted between trees almost exclusively by longhorn beetles of the genus Monochamus, including, in particular, M. galloprovincialis (Coleoptera: Cerambycidae) in maritime pine forests. Accurate estimates of the flight capacity of this insect vector are required if we are to understand and predict the spread of pine wilt disease in Europe. Using computer‐linked flight mills, we evaluated the distance flown, the flight probability and speed of M. galloprovincialis throughout adulthood and investigated the effects of age, sex and body weight on these flight performances, which are proxies for dispersal capacity. The within‐population variability of flight performance in M. galloprovincialis was high, with a mean distance of 16 km flown over the lifetime of the beetle. Age and body weight had a significant positive effect on flight capacity, but there was no difference in performance between males and females. These findings have important implications for managing the spread of the pine wood nematode in European forests.     

Effect of sex,age and morphological traits on tethered flight of Bactrocera dorsalis (Hendel) (Diptera: Tephritidae) at different temperatures

The oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), is a pest of fruit and vegetable production that has become established in 42 countries in Africa after its first detection in 2003 in Kenya. It is likely that this rapid expansion is partly due to the reported strong capacity for flight by the pest. This study investigated the tethered flight performance of B. dorsalis over a range of constant temperatures in relation to sex and age. Tethered flight of unmated B. dorsalis aged 3, 10 and 21 days was recorded for 1 h using a computerized flight mill at temperatures of 12, 16, 20, 24, 28, 32 and 36 °C. Variations in fly morphology were observed as they aged. Body mass and wing loading increased with age, whereas wing length and wing area reduced as flies aged. Females had slightly larger wings than males but were not significantly heavier. The longest total distance flown by B. dorsalis in 1 h was 1559.58 m. Frequent short, fast flights were recorded at 12 and 36 °C, but long-distance flight was optimal between 20 and 24 °C. Young flies tended to have shorter flight bouts than older flies, which was associated with them flying shorter distances. Heavier flies with greater wing loading flew further than lighter flies. Flight distances recorded on flight mills approximated those recorded in the field, and tethered flight patterns suggest a need to factor temperature into the interpretation of trap captures.     

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.     

Flight duration of the brown planthopper, Nilaparvata lugens (Homoptera: Delphacidae)

ABSTRACT.

• 1 The brown planthopper, Nilaparvata lugens (Stål), is a major pest of rice in Asia. It is known to make wind-assisted migratory flights each year to colonize the summer rice growing areas of China, Japan and Korea.
• 2 Modelling windborne displacements between rice growing areas in Asia requires migratory behaviour and flight duration to be established for this insect.
• 3 Field and laboratory observations suggest that N. lugens take-off at dusk and that some continue flying for up to 24–26 h if the temperature is ≥ 17°C.
• 4 Trajectories for 10 m above ground level and 1.5 km above mean sea level are used to identify possible sources and, hence, to estimate the flight times of N.lugens caught in nets on ships on the East China Sea in 1973 and 1981.
• 5 Estimated flight times between the sources and the ships ranged from about 9 to 30 h.
• 6 Results suggest that long-distance migration can occur in surface winds, when they are strong, but that long-distance migration is more likely at 1.5 km.
• 7 When simulating windborne displacements of N.lugens, it can be assumed that in areas and at heights where the temperature is ≥ 17°C, some migrants will fly downwind for up to 30 h after a dusk take-off. Others will fly for shorter periods, giving the population as a whole the opportunity to colonize all the rice crops flown over.

     

Prey preference and life tables of the predatory mite Parasitus bituberosus (Acari: Parasitidae) when offered various prey combinations

Parasitus bituberosus Karg (Acari: Parasitidae) is one of the predatory mite species inhabiting mushroom houses. It is known to accept a wide range of prey, suggesting that it may be a promising candidate for the biological control of key pests of mushroom culture. In our study it did not show any prey preference among four groups of small organisms often occurring in mushroom growth medium, namely rhabditid nematodes, pygmephorid mites, and sciarid and phorid fly larvae. Nevertheless, the type of food these predators fed on affects their development. The shortest egg-to-adult development time was obtained on a nematode diet. On a diet of phorid larvae, mite development stopped at the deutonymph stage; none reached adulthood. All other diets sufficed to reach the adult phase. Female fecundity when fed nematodes and sciarid larvae did not differ, but it was much lower when fed pygmephorid mites. Other life table parameters confirmed that pygmephorid mites constituted the worst diet for P. bituberosus. The highest intrinsic rate of population increase (r _m  = 0.34) was obtained on the nematode diet; when fed sciarid larvae and pygmephorid mites it was 0.25 and 0.14, respectively. Our study provides good reasons to further test P. bituberosus as biocontrol agent of especially sciarid flies and nematodes, especially when the compost is well colonized by mushroom mycelium (which retards nematode growth).