Biology, life table and host specificity of the mushroom pest, Brennandania lambi (Acari: Pygmephoroidea)

Biology and life table parameters of Brennandania lambi (Krczal) were studied at different temperatures while feeding on white mushroom (Agaricus bisporus) mycelium cultured on mushroom compost. The duration of egg and larva development, preoviposition and oviposition period, female longevity, and the time to 50% mortality declined as temperature increased from 16 to 28°C. The threshold temperature of development (female) was 9°C and the thermal constant for completion of development (female) was 195 day-degrees. At 16, 20, 24 and 28°C, the total fecundity (eggs/female) was 71, 67, 66 and 57, respectively and the daily fecundity rate (eggs/female/day) was 5.6, 8.7, 8.7 and 9.1, respectively. The sex ratio (female/male) ranged from 1.9 to 2.1 at 16–28°C. At 16, 20, 24 and 28°C, the intrinsic rate of natural increase (r _m) was 0.11, 0.18, 0.22 and 0.27, respectively, and the population doubling time was 6.1, 3.9, 3.2 and 2.5 days, respectively. All life stages of the mite died when exposed to 35°C constant temperature for 24h, or to 32°C constant temperature for 12 days or to 31–35°C (average 32.9°C) ambient temperature for 4 days. Brennandania lambi completed development only when fed on Ag. bisporus mycelium growing on mushroom compost. It could not survive on mushroom mycelia of Auricularia auricula, Au. polytricha, Ganoderma lucidum, Hericium erinaceus, Lentinus edodes, Pleurotus ostreatus, P. sajor-caju and Tremella fuciformis.     

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 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.     

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.     

Effect of spent mushroom compost tea on mycelial growth and yield of button mushroom (Agaricus bisporus)

Preliminary studies suggested that the use of compost tea made from spent mushroom substrate (SMS) may be regarded as a potential method for biologically controlling dry bubble disease in button mushroom. The aim of this study was to assess the effect of SMS compost tea on the host, the button mushroom, to ascertain whether the addition of these water extracts has a toxic effect on Agaricus bisporus mycelium growth and on mushroom yield. In vitro experiments showed that the addition of SMS compost tea to the culture medium inoculated with a mushroom spawn grain did not have an inhibitory effect on A. bisporus mycelial growth. The effect of compost teas on the quantitative production parameters of A. bisporus (yield, unitary weight, biological efficiency and earliness) was tested in a cropping trial, applying the compost teas to the casing in three different drench applications. Quantitative production parameters were not significantly affected by the compost tea treatments although there was a slight delay of 0.8-1.4 days in the harvest time of the first flush. These results suggest that compost teas have no fungitoxic effect on A. bisporus so that they can be considered a suitable biocontrol substance for the control of dry bubble disease.     

Optimization of the microemulsion formulation of curcuma oil and evaluation of its acaricidal efficacy against Tetranychus cinnabarinus (Boisduval) (Acari: Tetranychidae)

The microemulsion formulation (hereafter formulation) of curcuma oil and its acaricidal efficacy against Tetranychus cinnabarinus Boisduval (Acari: Tetranychidae) were optimized in the laboratory to evaluate their spray effectiveness of oviposition inhibition and repellence. Ethovision XT6 was used to analyse the effects of the sublethal concentrations (LC₂₀) of curcuma oil and the formulation on the behaviors of T. cinnabarinus. The results showed that Tween-80 was the best surfactant, Isopropanol was the best co-surfactant and K_m = 2:1 was the best condition for the formulation. The prepared microemulsions are stable under conditions of centrifugation and incubation for extended periods. The results showed that the effect of the spray bioassays of the formulation against T. cinnabarinus continuously increased during the experiment, but for curcuma oil almost no longer increase observed when the exposure time went beyond 24 h. Moreover, compared with curcuma oil (LC₅₀ = 0.716%), the spray bioassay of the formulation (LC₅₀ = 0.035%) was stronger against T. cinnabarinus. The repellency of the formulation to T. cinnabarinus was stronger with increasing exposure time, but that of curcuma oil declined after 12 h of exposure. The mobile distance of T. cinnabarinus treated with the formulation continuously declined during the experiment but that due to the curcuma oil almost no longer declined when the treatment time reached 12 h. The maximum mobile frequency of T. cinnabarinus treated by curcuma oil and the formulation was recorded at 6 h and 12 h, respectively. Thus, the formulation is a promising candidate as a botanical acaricide of green vegetables.     

Population characteristics of Macrocheles glaber (Acari: Macrochelidae) and Stratiolaelaps scimitus (Acari: Laelapidae) reared on a mushroom fly Coboldia fuscipes (Diptera: Scatopsidae)

Subterranean predatory mites are important biological control agents of pests in soil. In order to understand the population characteristics of two predatory mites, Macrocheles glaber Miiller and Stratiolaelaps scimitus Womersley, we studied their development, survival and fecundity data under laboratory conditions using Coboldia fuscipes Meigen as a food source and analyzed them with the age-stage, two-sex life table. Macrocheles glaber had a significantly shorter developmental time, oviposition period, longevity and lower fecundity than those of S. scimitus. The intrinsic rate of increase (λ), finite rate of increase (r), net reproductive rate (C0),net predation rate (C0), and finite predation rate (ω) of M. glaber were significantly lower than those of S. scimitus. Both population parameters and computer simulation implied that S. scimitus is a potential powerful biocontrol agent compared to M. glaber.     

Sublethal effects of esfenvalerate residues on pyrethroid resistant Typhlodromus pyri (Acari: Phytoseiidae) and its prey Panonychus ulmi and Tetranychus urticae (Acari: Tetranychidae)

The effect of residues of esfenvalerate on oviposition of the resistant strain of the predatory mite Typhlodromus pyri and its main prey, European red mite Panonychus ulmi and two-spotted spider mite Tetranychus urticae, were investigated. T. pyri showed a significant linear reduction in oviposition after 24h in the presence of increasing levels of esfenvalerate residue applied at the field rate. Furthermore, when given a choice, T. pyri preferred to lay eggs on residue-free surfaces. Of the two prey species, only P. ulmi showed significant avoidance of increasing levels of residues of the field rate concentration of esfenvalerate, as measured by runoff mortality, however both P. ulmi and T. urticae, when given a choice, showed a preference for esfenvalerate-free surfaces. As with the predatory mite T. pyri, both prey species showed a significant linear reduction of oviposition with increasing esfenvalerate residues and a preference to lay eggs on esfenvalerate-free surfaces. Esfenvalerate residues as high as 15X field rate were not repellent to pyrethroid-resistant T. pyri. The possible effects of these sublethal effects on predator-prey dynamics and implications for integrated mite control programmes in apple orchards are discussed.     

Comparative effects of Steinernema feltiae (Nematoda: Steinernematidae) and insecticides on yield and cropping of the mushroom Agaricus bisporus

In a mushroom crop (Agaricus bisporus) affected by a very low level of sciarid fly (Lycoriella auripila) infestation, the effects of an indigenous isolate of insect-parasitic nematode (Steinernema feltiae) and of two commonly used insecticides (diazinon and diflubenzuron) were studied. When compared with untreated plots, nematodes applied to the casing had no adverse effects on mushroom yields whereas insecticides decreased yields. At a rate of 3 × 10⁶ infective juveniles per tray (surface area = 0.56 m²), S. feltiae elicited increases of 28.5% and 19% in the mean total numbers and weights of mushrooms respectively. Treatment only with diflubenzuron resulted in 14.6% and 6% reductions in mean total numbers and weights of mushrooms, respectively; treatment with both diazinon and diflubenzuron caused 18.5% and 9.4% losses. Application of nematodes generally reduced the mean weight per mushroom whereas insecticides increased it; nematodes delayed the onset of mushroom production (first flush) whereas diflubenzuron delayed the third and fourth flushes. Nematode contamination of sporophores was minimal when S. feltiae was applied at casing. Although their numbers declined with time, the nematodes persisted, in the casing layer, throughout the cropping period of seven weeks. It is concluded that yield benefits associated with nematode application can result mainly from nematode effects on A. bisporus and not solely from suppression of a damaging pest population.     

Field evaluation of Beauveria bassiana efficacy for the control of Tetranychus urticae Koch (Acari: Tetranychidae)

Trials with eggplants were conducted to evaluate field efficacy of Beauveria bassiana (Bb) applications against Tetranychus urticae, during spring of 2006 and 2007. In the 2006‐Trial, a rate of ca. 0.7 × 10¹² conidia/ha was sprayed onto plants at intervals. In the 2007‐Trial, the rates of ca. 0.8 × 10¹² and 1.6 × 10¹² conidia/ha were sprayed at 1‐ or 2‐week intervals. Based on population densities of mites and leaf damage assessed throughout the trial, the Bb sprays with 1‐ or 2‐week interval showed better control than those of 3 or 4 weeks. In both trials there was no statistical difference between 1‐week and 2‐week spray interval for all parameters measured. Furthermore, the higher rate performed significantly better than the lower rate, regardless of the intervals. No interaction was found between the spraying interval and the applied rate. Ultimately, to suppress the population density of T. urticae and prevent the eggplant damage in spring, the higher rate applied at 2‐week interval was effective.     

The effects of spirotetramat on life history traits and population growth of Tetranychus urticae (Acari: Tetranychidae)

The effects of spirotetramat, a tetramic acid derivative, on gross fertility, net fertility, female longevity and the instantaneous rate of increase of two-spotted spider mite, Tetranychus urticae (Acari: Tetranychidae) were investigated after treatment of female teleiochrysalises (the first assay) and pre-ovipositional females (the second assay). Spirotetramat was applied to the leaf discs by Potter spray tower and the following series of concentrations was applied: 200, 60, 18, 5.4 and 1.62 mg/l. In both assays after 24 h of exposure, surviving females without symptoms of poisoning were used for further procedure. In the first assay, gross fertility of treated females was reduced by 2.4–64.7% and net fertility by 12.4–88.8%, compared to the control. Gross fertility of the females treated with 1.62 and 5.4 mg/l did not significantly differ from the control, whereas all concentrations, except the lowest, significantly reduced net fertility and female longevity. Treatments with 200, 60, and 18 mg/l significantly reduced the instantaneous rate of increase. In the second assay, gross fertility and net fertility were reduced by 43.7–93.3% and 73.8–98.5%, respectively. All concentrations, except the lowest, significantly reduced gross fertility, whereas net fertility and longevity in all treated females were significantly lower compared to the control. All concentrations, except the lowest, significantly reduced the instantaneous rate of increase, provided that concentrations of 200, 60 and 18 mg/l caused population decline. The effects of spirotetramat and its impact on T. urticae management are discussed.     

The effects of spiromesifen on life history traits and population growth of two-spotted spider mite (Acari: Tetranychidae)

Laboratory bioassays were conducted to evaluate the effects of spiromesifen on gross fecundity, gross fertility, net fertility and population growth of two-spotted spider mite (Tetranychus urticae Koch) after treatments with four acaricide concentrations: 180 mg/l, i.e. maximum recommended concentration for use in glasshouses against spider mites, 18, 1.8, and 0.18 mg/l, i.e. concentration discriminative for eggs and immatures in preliminary studies which produced 100% mortality of these stages. Quiescent female deutonymphs were treated in the first assay, and young pre-ovipositing females in the second and third, in which exposure lasted 6 h and 20 h, respectively. In the first assay, the 180, 18, and 1.8 mg/l concentrations significantly reduced gross fecundity (61–85%), gross fertility (64–87%) and net fertility (85–94%) of the surviving females. In the second one, only the highest concentration achieved a significant statistical reduction in gross fecundity (52%), gross fertility (67%) and net fertility (84%). In the third assay, fecundity and fertility reduction under the two highest concentrations was 98–99% and 93–98%, whereas it was 50–74% under the 1.8 mg/l concentration, and statistically different from control values. In all three trials, treatments with 180, 18, and 1.8 mg/l concentrations significantly reduced the instantaneous rate of increase. In the third assay, treatments with the two highest concentrations caused population decline. Sublethal activity of the 0.18 mg/l concentration was not found in any assay to be statistically significant. Sublethal effects of spiromesifen and its impact on T. urticae management are discussed.     

Impact of proteins and saccharides on mass production of Tyrophagus putrescentiae (Acari: Acaridae) and its predator Neoseiulus barkeri (Acari: Phytoseiidae)

Proteins and saccharides are the two most important nutrients of artificial insect diets. In this study, additional protein or saccharide sources were added to the diet, and their impact on the population increase of both the prey Tyrophagus putrescentiae Schrank (Acari: Acaridae) and the predator Neoseiulus barkeri Hughes (Acari: Phytoseiidae) was investigated. T. putrescentiae population increased by 319, 317 and 180 times within six weeks, when yeast powder, glucose or sugar was added to the basic wheat bran diet (diet mass: additive mass 10:3), respectively. However, T. putrescentiae population increased by only 70 times when reared on the basic diet. All three types of nutrients resulted in increased soluble saccharide level of mixed stages T. putrescentiae. Significant increase of soluble protein level was observed when yeast powder was added. When fed on T. putrescentiae reared on yeast powder, glucose or sugar added diets, the developmental duration of N. barkeri was shortened by 23, 23 and 33%, and the daily fecundity increased by 40, 20 and 27%, respectively. The proportion of N. barkeri female offspring was 64% when fed with T. putrescentiae reared on wheat bran, increased to 70% when yeast powder was added, and decreased to 59% and 58% when glucose and sugar was added, respectively. The commercial packaging requirement of N. barkeri is 80 mites per g. It generally takes 40 days from N. barkeri inoculation to reach this requirement, but this period was dramatically shortened to 20, 25 and 24 days when yeast powder, sugar and glucose were added to the diet of T. putrescentiae, respectively.     

Strain of Rhizobium effects on growth and seed yield of cowpeas (Vigna unguiculata)

Summary Plant of cowpea (Vigna unguiculata (L.) Walp.) cv. TVu 1469 were grown in a plastic house set to simulate tropical temperatures. They were inoculated with one of two strains of Rhizobium and irrigated each day with nutrient solution either devoid of inorganic nitrogen (N) or containing 2.14 mM (30 ppm) N. Strain of Rhizobium significantly affected rates of dry matter and N accumulation as well as the total N content of mature plants. Variations in seed yield were due largely to Rhizobium effects on peduncle production and pod set on each peduncle, wheres inorganic N did not change these yield-determining components significantly. The agronomic and physiological implications of these data are discussed. One of a series of papers resulting from a collaborative project with the International Institute of Tropical Agriculture, Nigeria; sponsored by the U.K. Overseas Development Administration.     

臭氧水对韭蛆的防治效果及对韭菜生长的影响

【目的】为科学合理地浇灌臭氧(O₃)水防治韭菜迟眼蕈蚊Bradysia odoriphaga幼虫(俗称韭蛆),明确最佳浇灌时期和使用条件。【方法】在平地覆膜环境中浇灌不同浓度(5, 10, 20和30 mg/L)O₃水,调查对韭蛆的防治效果;在平地覆膜环境中不同日光强度、3种不同灌溉环境［平地覆膜、小拱棚和小拱棚+草垫］、2种不同灌溉环境［平地覆膜、小拱棚］的不同浇灌频率等条件下分别浇灌30 mg/L O₃水,调查对韭蛆的防治效果;调查平地覆膜环境中浇灌30 mg/L O₃水对韭菜产量和根系生长的影响;分析日光强度对不同灌溉环境中土壤温度及浇灌O₃水对韭蛆的防治效果的影响。【结果】平地覆膜条件下,O₃水防治韭蛆的最佳浓度为20~30 mg/L。在平地覆膜条件下浇灌30 mg/L O₃水处理中,对韭蛆的防治效果与浇灌当天的日光强度呈正相关;当日光强度超过60 000 lx时,第1天韭蛆的死亡率高达100%;日光强度低于10 000 lx时,对韭蛆无显著的防治效果;日光强度处于中间水平时,前期对韭蛆的防治效果较差,而后期防治效果逐渐增强。土壤升温效果与日光强度呈正相关,也与灌溉环境显著相关,不同灌溉环境下土壤5 cm深处的温度为：平地覆膜>小拱棚＞小拱棚+草垫。小拱棚内浇灌O₃水对韭蛆的防治效果显著高于平地覆膜组和小拱棚+草垫组。采取连续多次浇灌O₃水有利于提高O₃水对韭蛆的防治效果,而且小拱棚内韭蛆的防治效果更显著。浇灌O₃水时,进水口离田埂末端的距离不能超过40 m。平地覆膜环境中浇灌30 mg/L O₃水后,韭菜的株高、重量和须根数量显著高于对照组(浇灌清水);韭菜植株分蘖数与对照组差异不显著。【结论】若能科学合理地浇灌O₃水,既能达到防治韭蛆的理想效果,又能促进韭菜生长。     

Biology of Agistemus brasiliensis Matioli, Ueckermann & Oliveira (Acari: Stigmaeidae) and its predation potential on Brevipalpus phoenicis (Geijskes) (Acari: Tenuipalpidae)

The present work aimed to study the biology of Agistemus brasiliensis Matioli, Ueckermann & Oliveira at the following temperatures, namely 15, 20, 25, 30 and 35 degrees C, fed with Brevipalpus phoenicis (Geijskes) and Typha pollen, in laboratory conditions. Life tables were calculated to evaluate the biological parameters. The optimal development of A. brasiliensis took place at 29 degrees C. The values of T (time of generation - days), R0 and r m at 30 degrees C were, 13.95, 16.25 and 0.20, respectively. The prey consumption of A. brasiliensis was studied at the densities of 5, 10, 20, 40 and 60 leprosis mite females per cage (3 cm in diameter) on citrus fruits at 29 degrees C. The maximum prey, namely 7.6 B. phoenicis females per day, were consumed at a density of 20 leprosis mites. At densities of above 40 leprosis mites per cage, A. brasiliensis oviposits 4.7 eggs per day, in comparison to 2.5 eggs per day at 20 mites per cage.     

Development of black dot disease (Colletotrichum coccodes (Wallr.) Hughes) and its effects on the growth and yield of potato plants

Seed tubers of cvs Désirée and Pentland Crown with different severities of black dot were planted in 1988 and 1989 at Rothamsted in fields in 4– or 7-course rotations, respectively. Tubers treated with prochloraz (1988) or imazalil (1989) were planted in some plots, and in others Colletotrichum coccodes inoculum was added to the soil at planting. In further experiments at Mepal, Cambridgeshire in 1989 and 1990 and at Rothamsted in 1990 on sites where potatoes had not been grown for more than 15 years, large amounts of inoculum were added to the soil around disease-free seed tubers of two (1989) or three (1990) cultivars at planting. In all experiments plants were sampled during the season and the effects of treatments on disease development, growth and yield were recorded. Disease on roots, stem bases and tubers was found early in the season and was more severe on Désirée than on Pentland Crown plants from fields in 4– or 7-course rotations. Severity increased throughout the season and with increasing amounts of disease on the seed tubers, especially with Desiree. Disease was also found on plants from disease-free tubers and was more severe in 1988 than 1989. At harvest, black dot on tubers was significantly more severe from severely affected than from disease-free seed, and was most severe where inoculum, especially large amounts, had been added at planting. Fungicide treatment decreased disease early in the season but had no effect on tuber infection at harvest. In 1989 the weight loss of seed tubers during sprouting increased with increasing amounts of black dot, but the disease had little effect on plant size through the season. At harvest the yield of ware tubers (>50 mm) decreased with severe disease but total tuber yields were not significantly affected. However, at harvest in 1988 severely affected seed yielded significantly less than healthy seed. Plants grown from mini-tubers were free from disease on sites where potatoes had not been grown for at least 15 years. Inoculum applied at planting caused severe disease on all cultivars in both years, whereas disease was slight on uninoculated plants. Inoculated plants senesced early at Mepal in 1990, but there were no significant differences in total tuber yield in any experiment. However, yields of ware tubers (>50 mm) were sometimes decreased and the total tuber number per plant increased.     

Predation of Galendromus helveolus (Acari: Phytoseiidae) on Brevipalpus californicus (Acari: Tenuipalpidae)

The false spider mite, Brevipalpus californicus (Banks), is a major citrus pest in Texas. This phytophagous mite causes damage to fruit, leaves and stems of citrus, and is also a vector of citrus leprosis virus. Galendromus helveolus (Chant) is one of the most prevalent predacious mite species found on Texas citrus. The predation potential of G. helveolus on different stages of B. californicus was evaluated in the laboratory. An individual immature G. helveolus mite consumed an average of 30.7 eggs, 53.6 larvae, or 22.7 nymphs of B. californicus before developing to an adult. An individual adult female G. helveolus consumed an average of 164.8 eggs, 369.6 larvae, or 80.9 nymphs of B. californicus. Both immature and adult G. helveolus never fed on adult stage of B. californicus and never completed development. The development times of the immature stages of G. helveolus were 4.5, 4.1 and 4.6 days when fed on eggs, larvae and nymphs of B. californicus, respectively. When G. helveolus fed on the larval stage of B. californicus, the adults had the longest longevity (18.5 days) and the highest fecundity (14.0 eggs/female).     

Influence of precipitated calcium carbonate (CaCO3) on shiitake (Lentinula edodes) yield and mushroom size

Synthetic substrate consisting of oak sawdust (50%), white millet (28%), winter rye (11%) and soft red wheat bran (11%) was non-supplemented or supplemented with 0.2%, 0.4% or 0.6% (dry weight basis) precipitated calcium carbonate (CaCO(3)). Shiitake (Lentinula edodes) was grown in two crops to determine the effect of three CaCO(3) levels on mushroom yield and size. Yields and biological efficiencies (averages for two crops) from substrates non-supplemented with CaCO(3) were lower by 14.1%, 18.4% and 24.9% compared to treatments supplemented with 0.2%, 0.4% and 0.6% CaCO(3), respectively. Mushroom size (weight) was larger with non-supplemented substrate (16.8 g) compared to substrate supplemented with 0.6% CaCO(3) (15.1 g). However, mushroom production was more consistent from crop to crop when 0.6% CaCO(3) was added to substrate.     

Differential impact of egg predation by Zetzellia mali (Acari: Stigmaeidae) on Metaseiulus occidentalis and Typhlodromus pyri (Acari: Phytoseiidae)

The differential impact of Zetzellia mali on the phytoseiids Metaseiulus occidentalis and Typhlodromus pyri was studied in the laboratory and by analysis of population from orchard plots that contained either phytoseiid, similar numbers of prey mites and high or low densities of Z. mali. Five hypotheses were evaluated to explain why Z. mali had more impact on M. occidentalis in the field than on T. pyri. Given equal opportunity, Z. mali adult females did not consume more M. occidentalis eggs than T. pyri eggs nor did adult females of either phytoseiid inflict greater mortality on Z. mali eggs or larvae through attack or consumption. There was no difference in the within-tree association of Z. mali adult females with eggs of either phytoseiid species nor were there differences in the way prey mites (all life stages) were spatially partitioned between adult female Z. mali as compared with adults and deutonymphs (combined) of either phytoseiid. The foraging area of adult female Z. mali and the oviposition locations of the two phytoseiids from both field and laboratory data were compared using spatial statistics. Metaseiulus occidentalis laid significantly more eggs in the primary foraging area of adult female Z. mali than T. pyri. This was the only factor identified which may explain the greater impact of Z. mali on M. occidentalis. The impact of these interspecific effects on the persistence of predatory mite guilds and biological control are discussed.