Miticide bioassays with spider mites (Acari: Tetranychidae): effect of test method,exposure period and mortality criterion on the precision of response estimates

Six different bioassay methods were evaluated using propargite (Omite 30% wettable powder (WP) and fenbutatin oxide (Torque 50% (WP) and 55% suspension concentrate (SC)) with twospotted spider mite, Tetranychus uriticae Koch (TSM) and European red mite, Panonychus ulmi Koch (ERM) to document their utility and precision for estimating median lethal concentrations (LC). For each method, two post-treatment exposure periods and mortality criteria were used. Post-treatment exposure period and mortality criterion had a significant influence on the precision of LC₅₀ estimates for all tested miticides with all bioassays methods. Twenty four hour (h) post-treatment exposure was found to be the most suitable for the slide dip and Petri dish methods while 48h was the most appropriate for leaf disc methods. Scoring moribund mites as dead was the most satisfactory criterion for ensuring that biossays were as simple and precise as possible. The Petri dish residue-Potter tower method (PDR-PT) estimated the responses of TSM and ERM to propargite with high precision. The same method was not as precise for fenbutatin oxide formulations. Because significant mite run-off occurred with the leaf disc methods, their precision was not fully established. The slide dip method gave less precise estimates of LC₅₀ values for propargite (WP) and fenbutatin oxide (WP), while the same method gave more precise LC₅₀ estimates for fenbutatin oxide (SC) than the PDR-PT method. The toxicity of candidate miticides was found to be method-and species-dependent.     

First detection of <Emphasis Type="Italic">Varroa destructor</Emphasis> resistance to coumaphos in Argentina

In Argentina, studies on Varroa destructor resistance to coumaphos are still unknown. At present, high infestation levels of V. destructor are being detected in colonies of Apis mellifera after treatment with this acaricide. The aim of the present study was to determine the LC₅₀ of coumaphos in V. destructor from four apiaries with high mite density after treatment with coumaphos. The LC₅₀’s were 112, 319, 127 and 133 μg/Petri dish for mites from the four apiaries. Significant LC₅₀ differences were detected between resistant and susceptible mites. LC₅₀ increased 197–559-fold when compared to the corresponding baseline, suggesting the development of resistance. These results are the first report of resistance to coumaphos in V. destructor in Argentina.     

Factors influencing host choice of the honey bee parasite Varroa jacobsoni Oud

Reproducing Varroa jacobsoni obtained from brood cells of Apis mellifera L. with 13–16 day old bees (pupae) and Varroa mites kept on adult bees for at least 8 days were simultaneously tested for their choice in three host types. Comparisons were made of attractiveness of Varroa jacobsoni to nurse bees, pollen foragers as to larvae from nearly capped brood cells. Host choices were observed in Petri dishes and in an Y-shaped olfactometer. Varroa jacobsoni obtained from capped brood cells showed a stronger preference for nurse bees in Petri dish simultaneous choice tests with pollen foragers or larvae than did mites which were previously kept on adult bees. In olfactometer simultaneous choice tests, the two mite test groups showed no clear difference in preferences for bees of different ages. The preference of Varroa jacobsoni for bees of different ages is therefore not only influenced by host factors but also by intrinsic factors in female mites that depend on the mite's reproductive stage.     

Semiochemicals Influencing the Host-finding Behaviour of Varroa Destructor

Studies of Varroa destructor orientation to honey bees were undertaken to isolate discrete chemical compounds that elicit host-finding activity. Petri dish bioassays were used to study cues that evoked invasion behaviour into simulated brood cells and a Y-tube olfactometer was used to evaluate varroa orientation to olfactory volatiles. In Petri dish bioassays, mites were highly attracted to live L5 worker larvae and to live and freshly freeze-killed nurse bees. Olfactometer bioassays indicated olfactory orientation to the same type of hosts, however mites were not attracted to the odour produced by live pollen foragers. The odour of forager hexane extracts also interfered with the ability of mites to localize and infest a restrained nurse bee host. Varroa mites oriented to the odour produced by newly emerged bees (<16 h old) when choosing against a clean airstream, however in choices between the odours of newly emerged workers and nurses, mites readily oriented to nurses when newly emerged workers were <3 h old. The odour produced by newly emerged workers 18–20 h of age was equally as attractive to mites as that of nurse bees, suggesting a changing profile of volatiles is produced as newly emerged workers age. Through fractionation and isolation of active components of nurse bee-derived solvent washes, two honey bee Nasonov pheromone components, geraniol and nerolic acid, were shown to confuse mite orientation. We suggest that V. destructor may detect relative concentrations of these compounds in order to discriminate between adult bee hosts, and preferentially parasitize nurse bees over older workers in honey bee colonies. The volatile profile of newly emerged worker bees also may serve as an initial stimulus for mites to disperse before being guided by allomonal cues produced by older workers to locate nurses. Fatty acid esters, previously identified as putative kairomones for varroa, proved to be inactive in both types of bioassays.     

Tebufenpyrad: compatibility with integrated mite control on apples

Successful integrated mite control (IMC) depends on the availability of acaricides which act selectively on pest mites with minimal effects on predators. Laboratory bioassays of tebufenpyrad against adult female Panonychus ulmi (Koch) provided baseline toxicity data and showed it to be highly active. Bioassays also showed tebufenpyrad was toxic to the predatory mite Typhlodromus pyri Scheuten but it was approximately 70 times less toxic to the predators than to P. ulmi at the lc ₅₀. Field trials using four concentrations of tebufenpyrad (10, 7.5, 5 and 2.5 g a.i./100 l) confirmed it was selectively more toxic to the pest mites than to predators and showed that it is compatible with IMC. It is suggested that a concentration of 5 g a.i./100 l would be suitable for IMC. A resistance management strategy for tebufenpyrad is proposed.     

Transfers ofVarroa mites from newly emerged bees: Preferences for age- and function-specific adult bees (Hymenoptera: Apidae)

Movements of the parasitic honey bee mite,Varroa jacobsoni (Oud.) were monitored in several assays as they moved among adult host honey bees,Apis mellifera. We examined the propensity of mites to leave their hosts and to move onto new bee hosts. We also examined their preference for bees of different age and hive function. Mites were standardized by selecting mites from newly emerged worker bees (NEWs). In closed jars, 50% ofVarroa left NEWs irreversibly when no physical path was present for the mites to return to the NEWs; about 90% of mites left newly emerged drones in identical assays. In petri dish arenas, mites were rarely seen off NEW hosts when monitored at 15-min intervals for 4 h; this was the case for single NEWs with one mite (NEWs+) and when a NEW+ and a NEW− (no mites) were placed together in a petri dish. When a NEW+ was held with either a nurse beeor a pollen forager, 25% of the mites moved to the older bees. When both a nurseand a pollen forager were placed in a petri dish with a NEW+, about 50% of the mites transferred to older bees; nurse bees received about 80% of these mites, whereas pollen foragers received significantly fewer mites (about 20%,P < 0.05). Most mite transfers occurred during the first 30 min after combining NEWs+ and test bees. When NEWs+ were combined with bees of known ages, rather than function, mites transferred more often to young bees than to older bees (1- and 5-day-old bees vs. 25-day-old bees,P < 0.05; 1-day-old vs. 13- and 25-day-old bees;P < 0.05). No differences in proportions of transferring mites were seen when the range of bee ages was ≤ 8 days (P > 0.05), implying that the factors mediating the mites’ adult-host preference change gradually with bee age. A possible chemical basis for host choice byVarroa is indicated by their greater propensity to move onto freezer-killed nurse bees than onto freezer-killed pollen foragers (P < 0.05) and by their lower movement onto heat-treated bees than onto control bees (P < 0.05). Bee age, hive function, and directional changes in cuticular chemistry are all correlated. Movements of newly emerged mites in relation to these variables may provide insights into their reproductive success inApis mellifera colonies.     

丁氟螨酯对二斑叶螨生长发育的影响

[目的]丁氟螨酯是一种新型酰基乙腈类非内吸性杀螨剂,对害螨的各个螨态都有很高活性,具有较高的应用价值.本文评价了丁氟螨酯对二斑叶螨生长发育的影响,以期为合理用药和二斑叶螨的综合防治提供理论依据.[方法]采用浸叶法测定丁氟螨酯对二斑叶螨成螨与卵的致死中浓度、雌成螨产卵量、各螨态存活率以及各发育历期的影响.[结果]经丁氟螨...     

Genetic improvement of Amblyseius finlandicus (Acari: Phytoseiidae): laboratory selection for resistance to azinphosmethyl and dimethoate

Amblyseius finlandicus (Oudemans) was selected in the laboratory for resistance to azinphosmethyl and dimethoate by subjecting adult females to increasing concentrations of dried residues of dimethoate and azinphosmethyl on detached bean leaves. The first eight selections were done with dimethoate. Slide-dip bioassays indicated selection with dimethoate increased dimethoate resistance 1.8-fold and azinphosmethyl resistance 2.6-fold. These resistances appeared to be quite stable: a 1.2 to 1.3-fold decrease in resistance ratios was observed in a subculture after 10 months without selections. No decrease was observed after 9 months without selections in a pooled colony that consisted of both resistant and susceptible mites. The dimethoate-selected colony was subsequently selected eight times with azinphosmethyl. About 15 % of the mites survived the last selection round with 2,500 ppm, which is 2.5 times the highest recommended field rate in Finnish apple orchards. At the end of the selection program, based on slide-dip bioassays, the total increase in resistance to dimethoate was about two-fold and to azinphosmethyl about 5.4-fold compared to the unselected base colony from which the selected colony was derived. The LC₅₀ value for azinphosmethyl was 14 times higher in the selected colony (451.3 ppm a.i.) compared to the most susceptible colony tested. A similar level of resistance to both pesticides was achieved after six azinphosmethyl selections on a mixed colony that was initiated by pooling mites from five field-collected colonies and the dimethoate-selected lines. Year-to-year variation in azinphosmethyl LC₅₀ values of the unselected base colony was high, with values varying from 83.8 to 348.7 ppm a.i., demonstrating the need to test a reference strain in each bioassay. Results of the azinphosmethyl selections and the subsequent slide-dip bioassays suggest that the resistant strain could tolerate field rates of azinphosmethyl (300–950 ppm a.i.) used in Finnish apple orchards.     

Toxicity effect of the acaricide fipronil in semi-engorged females of the tick Rhipicephalus sanguineus (Latreille, 1806) (Acari: Ixodidae): preliminary determination of the minimum lethal concentration and LC(50)

Chemical acaricides, especially fipronil (active ingredient of Frontline®), are still the most effective method to control tick populations. In this study, the effectiveness of fipronil was assessed in semi-engorged females of the tick Rhipicephalus sanguineus. A protocol for an in vitro bioassay (AIT) was developed, and the LC₅₀ (lethal concentration 50%) and 95% confidence interval were determined. Ticks were immersed in Petri dishes with different concentrations of fipronil or distilled water for 2 min, dried, and placed in an incubator for 7 days. Dead R. sanguineus females treated with the 14 concentrations of fipronil were counted daily. Mortality results were compared with the Probit analysis, and the LC₅₀ and 95% confidence interval were calculated, g (95): LC₅₀ = 9.647 (4.711 to 13.470). This study was aimed at developing a more appropriate and updated protocol for an in vitro bioassay (AIT – adult immersion test), and providing information on the toxic potential of fipronil (elimination of ectoparasites with lower concentrations) and sensitivity of ticks, especially R. sanguineus, a pest of great interest, due to its occurrence in urban environments.     

Effects of reducing sample size on density estimates of citrus rust mite (Acari: Eriophyidae) on citrus fruit: simulated sampling

The consequence of reducing sample size on the accuracy and precision of estimates of citrus rust mite, Phyllocoptruta oleivora (Ashmead), densities on oranges was investigated. The sample unit was a 1-cm2 surface area on fruit. Sampling plans consisting of 360, 300, 200, 160, 80, 48, 36, or 20 samples per 4 ha were evaluated through computer simulations by using real count data from 32 data sets of 600 sample units per 4 ha. The original and reduced sampling plans were hierarchical with different numbers of sample areas per 4 ha, trees per area, fruit per tree, and samples per fruit. Individual estimates (n=100 simulations per data set) using each plan were sometimes considerably below or above target densities. In an original set of count data with a mean of six mites per cm2, simulations of 36 samples per 4 ha produced individual estimates ranging from one to 16 mites per cm2, whereas 80 samples per 4 ha produced estimates ranging from two to 10 mites per cm2. The plans consisting of 36 or more samples were projected to provide precision levels of 0.25 (SEM/mean) or better at densities of five or more mites per cm2 based on log-data, a projection that needs to be verified under real-grove situations. Each plan consistently provided mite detection in these sampling simulations except those consisting of 20 or 36 samples, which sometimes failed to detect mites when the target density was less than five mites per cm2. The study provided insight into the probable precision, accuracy and detection thresholds for eight candidate sampling plans varying from relatively low to high resource input.     

The potential use of entomopathogenic nematodesagainst Typhaea stercorea

Four entomopathogenic nematode species, Steinernema carpocapsae, S. feltiae, Heterorhabditis bacteriophoraand H. megidis, were tested in a petri dish assay against larvae and adults of the hairy fungus beetle Typhaea stercorea. In general, adults were less susceptible than larvae and the LC₅₀ decreased with the duration of the exposure to nematodes. S. carpocapsae was the most effective species against adult beetles (LC₅₀ after 96 hours exposure =67 nematodes/adult). Against larvae S.carpocapsae and H. megidis were comparablyeffective with an LC₅₀ of 30 and 55nematodes/larvae, respectively. S. carpocapsaewas tested at 70 and 100% RH against adults in baits of either chicken feed or crushed wheat, both supplemented with horticultural capillary matting pieces in order to obtain a wet weight of 50–60%. At70% RH no significant effect of the nematodes was obtained due to desiccation of the bait. In chickenfeed at 100% RH the mortality reached 80% with 500nematodes/adult. In wheat significant mortality was obtained only at 5000 nematodes/adult. Heavy growth of mould probably limited the nematode infection. When the bait was used in tube traps, desiccation and growth of mould was prevented, but nematode efficacy dropped to 4.4% in the traps and 12% in the surrounding litter. This revised version was published online in July 2006 with corrections to the Cover Date.     

Development and dehiscence of the cephalothecoid peridium in Aporothielavia leptoderma shows it belongs in Chaetomidium

The development of the cephalothecoid peridium of Aporothielavia leptoderma was examined using light and electron microscopy. Early stages in ascoma initiation were consistent with previous reports for other species in the Chaetomiaceae. However, as young cleistothecia increased in size, clusters of peridial cells in the outer textura angularis elongated in a radial pattern around a central cell or cell cluster to form rosettes of relatively thick-walled segments that marked the central areas of incipient cephalothecoid plates. The external flank along median portions of the radial cells became thin walled and swelled outwards so that each plate became concave and was separated from adjacent plates by a more or less circular to polygonal ridge of knuckle-shaped swellings. When dry, mature peridia split apart along some of the ridges demarcating individual plates but an internal mechanism for liberating ascospores from the confines of the ascoma was not observed. Physical disturbance of mature cleistothecia by beetles, when enclosed together in a Petri dish, shattered the peridia, liberating the ascospores. Smaller insects were unable to cause disarticulation of the cephalothecoid plates. Because of the presence of an apical germ pore in the ascospores and morphological similarity to Chaetomidium arxii, the new combination Chaetomidium leptoderma (syn. Thielavia leptoderma) comb. nov. is proposed.     

Susceptibility of populations of Banks grass mites (Acari: Tetranychidae) suspected of developing bifenthrin resistance from three maize fields

Banks grass mite, Oligonychus pratensis (Banks), from three Texas maize fields were assayed for bifenthrin resistance following poor field control in 1995. Laboratory bioassays showed the field mites to be 3- to 23-fold more tolerant to bifenthrin than the susceptible laboratory culture. Comparison of LC₅₀ values to assays with bifenthrin from 1985 to 1993 indicated no statistically significant changes in mite resistance. However, high LC₉₀ values in 1995 suggest possible resistance development. The percentages of resistant mites from the three fields in 1995 were calculated to be 4.7%, 17.9%, and 30.9%. The Banks grass mite population exhibiting the highest level of tolerance to bifenthrin was further assayed to evaluate tolerance levels to other insecticides alone and in combination with synergists and insecticides. A high level of tolerance existed in the 1995 ‘bifenthrin–selected’ Banks grass mite strain to bifenthrin, dimeothate, and amitraz. The combination of bifenthrin or dimethoate with a synergist indicated changes in the ability of the more resistant 1995 mites to detoxify insecticides. The activity of a dimethoate + bifenthrin mixture and a three way mixture of dimethoate, bifenthrin, and piperonyl butoxide caused 5- and 38-fold increase in toxicity against the more resistant Banks grass mite. This revised version was published online in July 2006 with corrections to the Cover Date.     

Selection of entomopathogenic fungi for use in combination with sub-lethal doses of imidacloprid: perspectives for the control of the leaf-cutting ant <Emphasis Type="Italic">Atta sexdens</Emphasis><Emphasis Type="Italic">rubropilosa</Emphasis> Forel (Hymenoptera: Formicidae)

In the first part of this study, four isolates of the fungus Beauveria bassiana (Bals.) Vuillemin (LPP1, LPP2, CG05 and CG24) and one isolate of Metarhizium anisopliae (Metsch.) Sorokin (CG46) were tested against adult foragers of Atta sexdens rubropilosa. Ants were allowed to walk on filter paper discs, inside Petri dishes, previously impregnated with 1 ml of a conidia suspension (2 × 10⁷ conidia ml⁻¹), maintained at 80% RH and 26°C for 24 h and subsequently, transferred to sterile Petri dishes, maintained at 23°C, 80% RH, 24 h dark. The mean values of LT₅₀ for LPP2, LPP1, CG46, CG24 and CG05 were 3.5, 3.7, 3.8, 4.2 and 4.4 days, respectively. Control insects for all tests in this study showed less than 10% mortality. Experiments were carried out to test the toxicity of imidacloprid (IMI) to A. sexdens rubropilosa. Mortality was evaluated 10 days following a 24 h exposure to the insecticide. Percent mortality caused by 500, 200, 100 and 10 ppm IMI was 77.8, 56.7, 45.5 and 5.5 respectively. Insects treated with 10 ppm IMI were observed to have reduced locomotor activity 24 h after exposure to the insecticide. The LC₅₀ of IMI was 154.3 ppm. Subsequent tests were carried out to evaluate the combination of a sub-lethal dose of IMI (10 ppm) and infection by CG24 (1 × 10⁷ conidia ml⁻¹). Mortality due to fungal infection alone was 43.3%. Mortality of insects treated with IMI followed by exposure to the fungus was 64.3%. These results indicate that IMI significantly increases the susceptibility of ants to infection by B. bassiana CG24.     

Virulence of entomopathogenic nematodes to larvae of the guava weevil, Conotrachelus psidii (Coleoptera: Curculionidae), in laboratory and greenhouse experiments

The guava weevil, Conotrachelus psidii, is a major pest of guava in Brazil and causes severe reduction in fruit quality. This weevil is difficult to control with insecticides because adults emerge over a long period, and larvae develop to the fourth-instar inside the fruit and move to the soil for pupation. We assessed the virulence of entomopathogenic nematodes to fourth-instar larvae in soil by comparing their susceptibility to nine species or strains: Heterorhabditis bacteriophora HP88, H. baujardi LPP7, and LPP1, H. indica Hom1, Steinernema carpocapsae All and Mexican, S. feltiae SN, S. glaseri NC, and S. riobrave 355. In petri dish assays with sterile sand at a concentration of 100 infective juveniles (IJs) of a given nematode species/strain, larval mortality ranged from 33.5 to 84.5%, with the heterorhabditids being the most virulent. In sand column assays with H. baujardi LPP7, H. indica Hom1, or S. riobrave 355 at concentrations of 100, 200, and 500 IJs, mortality was greater than the control only for H. baujardi (62.7%) and H. indica (68.3%) at the highest concentration. For H. baujardi LPP7 in a petri dish assay, the time required to kill 50 and 90% of the larvae (LT₅₀ and LT₉₀) for 100 IJs was 6.3 and 9.9 days, whereas the lethal concentration required to kill 50 and 90% of the larvae (LC₅₀ and LC₉₀) over 7 days was 52 and 122.2 IJs. In a greenhouse study with guava trees in 20-L pots, 10 weevil larvae per pot, and concentrations of 500, 1000 or 2000 IJs, H. baujardi LPP7 caused 30 and 58% mortality at the two highest concentrations. These results show that H. baujardi is virulent to fourth-instar larvae and has potential as a biological control agent in IPM programs.     

Acute and Sub-lethal Toxicity of Landfill Leachate Towards Two Aquatic Macro-invertebrates: Demonstrating the Remediation Potential of Aerobic Digestion

A specific landfill leachate that contained 1.036 mgl⁻¹of 2-chlorobiphenyl was used in the study (255 mg l⁻¹ COD and 133 mg l⁻¹ BOD₅). Three, 2-l semi-continuous batch reactors (SBRs) were used to simulate the treatment potential of this method on a small scale. Aerobic digestion effectively reduced the leachates COD concentration. Regardless of dilution, the leachates COD reached a <20 mg l⁻¹ equilibrium after 96 h exposure to aerobic digestion, however, increasing the level of dilution accelerated the process. In untreated leachate, the LC₅₀ for Asellus aquaticus was 57% v/v leachate in deionised water and 5% for Gammarus pulex (96 h, static LC₅₀ tests without nutrition and oxygen depleting conditions). After being exposed to aerobic digestion, these values rose to 95% and 40%, respectively. Prolonged exposure to a 1:20 sub-lethal dilution of the aforementioned leachate has been previously shown to affect the breeding colony size of Asellus aquaticus and a 1:66 dilution influenced the fecundity of a Gammarus pulex population. After remediation by aerobic digestion, however, the population dynamics of both test species remained unaltered.     

Susceptibility of Helicoverpa zea and Heliothis virescens (Lepidoptera: Noctuidae) to Vip3A insecticidal protein expressed in VipCot™ cotton

Susceptibility of laboratory and field colonies of Helicoverpa zea (Boddie) and Heliothis virescens F. to Vip3A insecticidal protein was studied in diet incorporation and diet overlay assays from 2004 to 2008. Responses of field populations were compared to paired responses of University of Arkansas laboratory susceptible H. zea (LabZA) and H. virescens (LabVR) colonies. After 7 d of exposure, observations were made on number of dead larvae (M) and the number of larvae alive but remaining as first instars (L1). Regression estimates using M (LC₅₀) and M plus L1 (MIC₅₀) data were developed for laboratory and field populations. Susceptibility of laboratory and field populations exposed to Vip3A varied among different batches of protein used over the study period. Within the same batch of Vip3A protein, susceptibilities of laboratory colonies of both species (LabZA and LabVR) were similar. Field colonies were significantly more susceptible to Vip3A than the respective reference colonies of both species. Within field populations, susceptibility to Vip3A varied up to 75-fold in H. zea and 132-fold in H. virescens in LC₅₀ estimates. Variabilities in MIC₅₀s were up to 59- and 11-fold for H. zea and H. virescens, respectively.     

Pathogenicity of <Emphasis Type="Italic">Beauveria bassiana</Emphasis> and <Emphasis Type="Italic">Metarhizium anisopliae</Emphasis> to the tobacco spider mite <Emphasis Type="Italic">Tetranychus evansi</Emphasis>

Seventeen isolates of Metarhizium anisopliae (Metschnikoff) Sorokin and two isolates of Beauveria bassiana (Balsamo) Vuillemin were evaluated for their pathogenicity against the tobacco spider mite, Tetranychus evansi Baker & Pritchard. In the laboratory all the fungal isolates were pathogenic to the adult female mites, causing mortality between 22.1 and 82.6%. Isolates causing more than 70% mortality were subjected to dose–response mortality bioassays. The lethal concentration causing 50% mortality (LC₅₀) values ranged between 0.7×10⁷ and 2.5×10⁷ conidia ml⁻¹. The lethal time to 50% mortality (LT₅₀) values of the most active isolates of B. bassiana and M. anisopliae strains varied between 4.6 and 5.8 days. Potted tomato plants were artificially infested with T. evansi and treated with B. bassiana isolate GPK and M. anisopliae isolate ICIPE78. Both fungal isolates reduced the population density of mites as compared to untreated controls. However, conidia formulated in oil outperformed the ones formulated in water. This study demonstrates the prospects of pathogenic fungi for the management of T. evansi.     

Infectivity of two members of theEntomophthora muscae complex [Zygomycetes: Entomophthorales] forMusca domestica [Dipt.: Muscidae]

Dose-mortality studies were conducted with 2 members of theEntomophthora muscae (Cohn) Fresenius complex from southern California (CA) and Denmark (DA) infecting house flies,Musca domestica L., from southern California. Primary conidia of the DA form were significantly more infective (LC₅₀=34 conidia/mm²) than primary conidia of the CA form (LC₅₀=67 conidia/mm²) for 2–7 days old (‘young’) flies. Infectivity (single experimental trial) for 10–14 day old (‘old’) flies of primary conidia of the CA form (LC₅₀=34 conidia/mm²) was similar to that of the DA form for young flies. Secondary conidia of the CA form were markedly more infective (LC₅₀=0.36 conidia/mm²) than primary conidia of either form. Dose had no significant effect on incubation period for primary conidia of either form, but increased doses resulted in significantly shorter incubation periods for flies exposed to secondary conidia of the CA form.      

Experimental method for isolating and identifying dust mites from sputum in pulmonary acariasis

The aim of this study was to pilot a simpler and more effective method for identifying dust mites in sputum. Dust mites and their allergens have been implicated in respiratory diseases, including pulmonary acariasis, and several studies have identified mites in sputum. Further research is dependent on the development of a faster and simpler diagnostic test. We have demonstrated that dust mites artificially introduced into sputa, could be identified after the sputa were liquefied with bleach, when the liquid sample was observed under the microscope. Liquefaction times for serous, mucous, purulent and hemoptoic sputa varied from 10 to 30 min (mean 17.5). The test had a sensitivity of 80% (95% CI 68.2–88.2%) as 46/60 mites were identified. This procedure can be performed quickly at room temperature, is simple, inexpensive, repeatable, and less labourious than previous methods.