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PubMed1992

Ectoparasitic mites (Acari) of sympatric Brazilian free-tailed bats and big brown bats in Alabama.

Seven species of mites were recovered from 133 Brazilian free-tailed bats, Tadarida brasiliensis, and 94 big brown bats, Eptesicus fuscus, from February through November 1990 in colonies that shared roosting space in east-central Alabama. The macronyssid Chiroptonyssus robustipes (Ewing) was the most common mite on T. brasiliensis (964 mites, 87% of bats infested) and on E. fuscus (109 mites, 29% of bats infested). However, C. rubustipes normally is a specific parasite of T. brasiliensis. The macronyssids Steatonyssus ceratognathus (Ewing) and S. occidentalis (Ewing) were recovered from both species of bats in low numbers. S. ceratognathus is not a typical parasite of either species of bat, but S. occidentalis normally is specific to E. fuscus. Predictably, S. occidentalis was most frequently collected from E. fuscus (16 mites, 9% of bats infested), but two specimens were recovered from T. brasiliensis. Five specimens of the laelapid Androlaelaps casalis (Berlese) (a mite that is frequently associated with rodents) and one specimen of the myobiid mite Ewingana (Doreyana) longa (Ewing) (a specific ectoparasite of T. brasiliensis) were also recovered from T. brasiliensis. Singletons of the rosensteiniids Mydopholeus sp. and Nycteriglyphites pennsylvanicus Fain, Lukoschus & Whitaker were the only additional mites collected from E. fuscus; both of these mites have previously been collected from bats or their guano but are recorded here from Alabama for the first time. With respect to ectoparasite cross-infestations, E. fuscus appears to be at greater risk from sharing roots with T. brasiliensis. This is highlighted by the comparatively large numbers of C. robustipes that occurred on E. fuscus and the low numbers of S. occidentalis on T. brasiliensis. Although mites were the only arthropods recovered from bats in this study, a separate survey in 1991 revealed that the bat bug Cimex adjunctus Barber infested some other colonies of T. brasiliensis and E. fuscus in Alabama.

Alabama↗
PubMed1997

Fauna and geographical distribution of house dust mites in Korea.

During the period of 1933-1994, house dusts were collected from 65 homes at 10 different localities by operating electric vacuum cleaners. House dust mites were isolated from 10 g dust by applying the modified wet sieving method. Total 7,257 mites were collected and 23 species were identified. Among them. Dermatophagoides farinae (DF) was predominant (65.3% of the total), followed by D. pteronyssinus (DP) (20.6%) and Tyrophagus putrescentiae (TP) (6.5%). Rhizoglyphus robini. Sancassania phyllophagianus, Cheyletus traussarti and Scheloribates latipes were the first findings from Korea. DF was predominant in Seoul (66.8%). Kwangju (63.6%), inland of Pusan (79.6%), Inchon (96.5%). Taejon (83.9%), Chonju (87.15) and Chongju (95.2%), whereas DP was predominant in Yongkwang-ub (72.5%) and Yongdo (island) of Pusan (64.9%), and TP in Chunchon (38.2%). The localities where DP and TP were predominant showed higher relative humidity in air (> 73% RH). Among 62 study homes, DF, DP and TP were found in 24.6% of the homes, co-habitat of two species in 48.1% and one species in 27.3%. DF was predominant in 63.5% of the homes studied. DP in 29.6% and TP in 6.9%. In 10 g of the house dust, less than 99 mites were found in 49 homes (70.0%), 100-499 mites in 11 homes (15.7%). 500-999 mites in 3 homes (4.3%) and more than 1,000 mites in 2 homes (2.9%). No mite was found in 5 homes (7.1%). In order to evaluate environmental factors affecting the population density of house dust mites, house type, age of house construction, size of the house, number of the family and frequency of the cleaning were compared with the number of mites, and none of the above factors were statistically correlated with the mite density.

Animals↗
PubMed2005

Caste, sex and strain of honey bees (Apis mellifera) affect infestation with tracheal mites (Acarapis woodi).

Worker honey bees from genetic strains selected for being resistant (R) or susceptible (S) to tracheal mites typically show large differences in infestation in field colonies and in bioassays that involve controlled exposure to infested bees. We used bioassays exposing newly emerged individuals to infested workers to compare the propensity for tracheal mites to infest queens, drones and workers from R and S colonies. In tests with queens, newly emerged R and S queens were either simultaneously confined in infested colonies (n = 95 and 87 respectively), or individually caged with groups of 5-20 infested workers (n = 119 and 115 respectively). Mite prevalence (percentage of individuals infested) and abundance (foundress mites per individual) after 4-6 days did not differ between R and S queens. In another test, five newly emerged drones and workers from both an R and an S colony, and a queen of one of the two strains, were caged in each of 38 cages with 20 g of workers infested at 60-96% prevalence. Infestations of the R queens (n = 17) and S queens (n = 19) did not differ significantly, but R workers had half the mite abundance of S workers, while R drones received about a third more migrating mites than S drones. In tests to evaluate possible mechanisms, removal of one mesothoracic leg from R and S workers resulted in 2- to 10-fold increase in mite abundance on the treated side, but excising legs did not affect infestation of the corresponding tracheae in drones. This suggests that differences in infestation between R and S workers, but not drones, are largely determined by their ability to remove mites through autogrooming. If autogrooming is the primary mechanism of colony resistance to tracheal mites, selection for resistance to tracheal mites using infestation of hemizygous drones may be inefficient.

Animals↗
PubMed2006

The ecological distribution of reproductive mode in oribatid mites, as related to biological complexity.

The high incidence of asexuality in oribatid mites presents an unusual opportunity for examining hypotheses for the maintenance of sex. There is a presumed range in age of asexual species: many oribatid species are phylogenetically clustered, occurring in speciose early-derivative families or genera without sexual species, while others are phylogenetically isolated from other asexual species, occurring in later derivative taxa with sexual congeners. We examined the distribution of oribatid mite reproductive mode in soil of corn fields, grassy and shrub fields, and forests in central New York State (three replicate plots of each type, with 25 samples per plot), to test three ecological predictions from current theory. (1) If overall biotic uncertainty, as generated by competitors and predators, mediates the ecological distribution of oribatid mites, then the proportion of asexual oribatid mites should be negatively correlated with biological diversity; we examine this prediction using literature data as well. (2) If Muller's Ratchet (the stochastic loss of best genotypes, which is independent of environment), mediates the success of asexuality, then no ecological pattern should exist. (3) If general purpose genotypes are characteristic of asexual oribatid mites, their habitat distribution should be broader than that of sexual species. For each plot the level of asexuality was compared to indices of overall biotic diversity, as calculated from the pooled oribatid mite (competitors) and mesostigmatid mite (predator) communities. We found no negative correlation in this relationship in our own data or in the literature analysis of 290 faunal surveys from 50 literature sources, so we reject biotic uncertainty as an important determinant of reproductive mode distribution. When only data on phylogenetically clustered asexuals are considered, there is instead a positive correlation between asexuality and diversity that is not explained. Because of the latter pattern we tentatively reject Muller's Ratchet as the primary factor maintaining reproductive mode in these mites, but cannot reject it for isolated asexual species. Niche breadth in sexual and asexual oribatid mites provides no support for widespread general purpose genotypes but broad patterns in the literature suggest that the idea needs further investigation. Possible complicating or unknown factors that are discussed include historical disturbance in the study area, the relationship between parasitism and general biotic diversity, and the level and source of genetic diversity in asexual oribatid mites.

Animals↗
PubMed2006

Stimulation of the in vitro migration of ovine eosinophils by factors derived from the sheep scab mite, Psoroptes ovis.

The ectoparasitic astigmatid mite Psoroptes ovis causes sheep scab, a highly contagious, severe allergic dermatitis associated with damage to the fleece and hide, loss of condition and occasional mortality. The scab lesion is characterized by a massive infiltration of eosinophils that begins very rapidly after infection. This paper reports the finding that mite-derived factors directly enhance the migration of ovine eosinophils in vitro. Significant (p < 0.01) and dose-dependent (r = 0.972 +/- 0.018 (SD)) activity was initially identified in whole mite extracts, by comparison with medium controls in an assay based on modified Boyden chambers and ovine bone marrow target cells. Similar pro-migratory activity (p < 0.005; r = 0.928 +/- 0.069 (SD)) was detected in washes containing mite excretory/secretory material. By direct comparison with migration ratios (n = 3) for defined chemotactic (rmeotaxin = 3.430 +/- 0.360 (SD)) and chemokinetic (rminterleukin-5 = 0.982 +/- 0.112 (SD)) stimuli it was determined that the activity in both mite extracts (0.992 +/- 0.038 (SD)) and mite washes (0.969 +/- 0.071 (SD)) was chemokinetic. Subsequent experiments (n = 3) in which live mites were incorporated directly into the in vitro assay system indicated that they produced factors that significantly (p < 0.001) enhanced eosinophil migration to a degree directly related to mite numbers (r = 0.993 +/- 0.005 (SD)). The identity of the factor(s) responsible is uncertain, but their presence suggests that mites may be capable of directly activating eosinophils in vivo, and raises the possibility that mites could directly influence, perhaps even initiate, the rapid early tissue eosinophilic response observed in experimental sheep scab infections.

Animals↗
PubMed1981

Lymphocyte responsiveness to Dermatophagoides farinae extract in mite-sensitive patients: effect of immunotherapy on cellular proliferative response and specific immunoglobulin E antibody (RAST score).

Lymphocyte responsiveness in vitro and serum levels of specific IgE antibody to mite extracts (Dermatophagoides farinae) were evaluated in mite-sensitive asthmatic patients and in nonatopic individuals. Lymphocytes from untreated mite-sensitive patients (n = 16) responded to mite extracts with greater 3H-thymidine uptake than those from nonatopic individuals (n = 20; p less than 0.01). Specific IgE antibody and total IgE levels were significantly higher in mite-sensitive patients than those in nonatopic individuals. These results suggest that mite-sensitive patients respond to mite allergen with exaggerated lymphocyte proliferation as well as with enhanced specific IgE antibody production. Lymphocyte response to mite extracts was significantly lower in the patients with long-term dust immunotherapy than that in the untreated patients (p less than 0.05), but there was no significant difference in the total IgE and the specific IgE antibody levels between them. Lymphocyte response to Candida albicans was not significantly affected in these patients. These results suggest that as far as mite allergy is concerned, there is some difference in the effect of immunotherapy between lymphocyte proliferative response and specific IgE antibody to mite allergen.

Animals↗
PubMed1982

The prevalence of house dust mites, Dermatophagoides spp, and associated environmental conditions in homes in Ohio.

Abundance of the house dust mites, Dermatophagoides farinae and D. pteronyssinus, in various sites in the homes of dust-sensitive patients was sequentially monitored at approximately 3 wk intervals for 2 yr, and mite density was correlated with indoor physical and climatic factors. Significantly higher mite levels occurred on the most heavily used fabric-upholstered furniture and carpeted floor areas of the living/family room and bedrooms. Mattresses were not found to be the major foci for mites. No significant positive correlation was noted between mite abundance and frequency or thoroughness of cleaning, amount of dust, and age of furnishings or dwelling. Significantly higher mite levels occurred on carpeted floors than on noncarpeted floors. Successive vacuuming did not significantly reduce mite abundance. Mite density exhibited a seasonal fluctuation, with highest density occurring in the humid summer months and the lowest density during the dryer, late heating season. Live mites were more abundant than dead mites during the period when total abundance was high. In homes inhabited by both species, D. farinae was the dominant species, except in one home that had a significantly higher relative humidity.

Animals↗
PubMed1988

Natural immunity to dust mites in patients with chronic rhinosinusitis.

Chronic rhinosinusitis is an extremely common clinical problem of which the etiology is poorly understood. To understand the role of common environmental antigens in this disease, natural immunity to antigens derived from the house dust mite was evaluated in 22 adults with chronic rhinosinusitis and compared to a carefully matched group of patients with chronic asthma or to a group of normal individuals. Allergic reactivity to dust mites was very common in patients with chronic rhinosinusitis, with 68% exhibiting a positive immediate skin test reaction and 41% exhibiting elevated levels of mite-specific serum IgE; 72% of patients with rhinosinusitis also exhibited markedly elevated levels of mite-specific serum IgG, which were present in both mite-allergic and nonallergic patients. IgG titers were much higher in the group with rhinosinusitis than in patients with asthma, whereas allergic reactivity to dust mites was significantly higher in the patients with asthma. Mite-specific immunity was low or absent in the group of normal individuals. These findings demonstrate that natural immunity to dust mites is very common in patients with chronic rhinosinusitis and suggest that immunity to mites may be involved in this syndrome. Furthermore, the data indicate that there may be significant differences in the ability of patients with rhinosinusitis or asthma to produce mite-specific antibodies of the IgG class.

Adult↗
PubMed1993

The Demodex mite population in rosacea.

BACKGROUND: The cause of rosacea is unknown; among other factors a causative role has been postulated for the hair follicle mites Demodex folliculorum and Demodex brevis. OBJECTIVE: Our purpose was to compare the population density of Demodex mites in facial skin of defined categories of patients with rosacea with control subjects. We also assessed the impact of tetracycline therapy on the mite population. METHODS: The population density and distribution of Demodex mites were studied in the facial skin of 42 patients with rosacea and 42 age- and sex-matched control subjects. Mites were counted in measured skin surface biopsy specimens obtained from six standard facial sites with cyanoacrylate glue. RESULTS: The mean mite count was 49.8 (range 2 to 158) in patients with rosacea and 10.8 (range up to 97) in control subjects (p < 0.001); the highest density of mites was found on the cheeks. A statistically significant increase in mites was found in all subgroups of rosacea, being most marked in those with steroid-induced rosacea. Mite counts in patients with rosacea before and after a 1-month course of oral tetracycline showed no significant difference. CONCLUSION: Increased mites may play a part in the pathogenesis of rosacea by provoking inflammatory or allergic reactions, by mechanical blockage of follicles, or by acting as vectors for microorganisms.

Adult↗
PubMed1996

Exposure to house dust mite allergens and the clinical activity of asthma.

BACKGROUND: House dust mite allergens play an important role in inducing IgE-mediated sensitization and the development of bronchial hyperresponsiveness (BHR) and asthma. This study investigated the relationship between mite allergen exposure and the clinical activity and severity of asthma. METHODS: Nonsmoking adult patients with asthma (n = 53) were randomly recruited from the asthma registry of two large family practitioner surgeries. Each participant underwent skin testing with common inhalant allergens, a methacholine bronchoprovocation test, and pulmonary function testing on up to 3 separate occasions over a 4-week period. BHR was expressed both as PD20 and dose-response ratio (DRR), and the patients with patients with PD20 of less than 12.25 mumol methacholine were classified as methacholine reactors. Patients were also asked to record peak expiratory flow rate (PEFR) values at 2-hour intervals during waking hours for 1 month. Daily PEFR variability was calculated as amplitude percent mean. Dust samples were collected by vacuuming bedding, bedroom carpets and mattresses. In addition, in the homes of 32 subjects with positive skin test responses to mites, airborne samples were taken overnight for 8 hours with a personal sampler attached to each subject's pillow. Der p 1 and Der p 2 levels were determined by a two-site monoclonal antibody-based ELISA. RESULTS: No difference in mite exposure was found between subjects who were sensitive to mites and those who were not. However, mite-sensitive methacholine reactors were exposed to significantly higher concentrations of Der p 1 in beds than mite-sensitive methacholine nonreactors (13.2 micrograms/gm and 1.45 micrograms/gm, respectively; p < 0.02). Der p 1 and Der p 2 were undetectable in 30 of 32 airborne samples. In mite-sensitive patients both Der p 1 and Der p 2 in beds significantly correlated with BHR (PD20: r = -0.49, DRR, r = 0.49; PD20: r = -0.46, DRR: r = 0.43) and amplitude percent mean PEFR (r = 0.38, r = 0.41) for Der p 1 and Der p 2, respectively. There was a significant negative correlation between exposure to Der p 1 and percent predicted FEV1 (r = -0.43). The correlation between Der p 2 and percent predicted FEV1 just failed to reach a significant level but showed a clear trend ( r = -0.35, p = 0.068). CONCLUSIONS: Clinical activity and severity of asthma (measured by the level of BHR, PEFR variability, and percent predicted FEV1) in mite-sensitive patients is related to exposure to mite allergens in the dust reservoir, with levels in bed being an important indicator that correlated with disease activity.

Adult↗
PubMed1997

Continuous avoidance measures with or without acaricide in dust mite-allergic asthmatic children.

BACKGROUND: Improvement in the quality of life in the Western world and increased time spent indoors by children have enhanced the spread of house dust mites and increased the exposure time for sensitive children. Also, exposure to house dust mites in infancy and subsequent development of childhood asthma have been clinically linked. Recently, new acaricides have been developed. OBJECTIVE: To test the efficacy of the new acaricide (esdepallethin and piperonyl butoxide--"Acardust") combined with environmental control compared with continuous house dust mite avoidance measures. METHOD: Forty-six house dust mite-allergic, asthmatic children were evaluated for 6 months in a prospective, randomized, double-blind, and placebo-controlled study. Patients were randomly allocated to active and placebo acaricide treatment combined with avoidance measures, whereas only continuous avoidance measures were taken in the third group. Symptom score, medication usage, and peak flow measurements were recorded daily. The amount of house dust mite allergen in the dust vacuumed from the bedrooms was also measured. RESULTS: Morning and evening peak expiratory flow rates and forced expiratory volume in one second remained unchanged throughout the study period. In all groups, the symptom scores improved significantly, whereas the amount of house dust mite allergen decreased significantly at the end of the trial. CONCLUSIONS: Continuous house dust mite avoidance measures have a significant positive effect on the symptomology of children with mild or moderate asthma. "Acardust" combined with continuous house dust mite avoidance measures is not more effective than continuous house dust mite avoidance measures alone in the treatment of house dust mite-allergic, asthmatic children.

Aerosols↗
PubMed1996

Effect of application of benzyl benzoate on house dust mite allergen levels.

BACKGROUND: Several acaricides have become available for reducing house dust mite allergen levels. OBJECTIVE: The purpose of this study was to assess whether the use of benzyl benzoate (Acarosan) provides additional benefit to the usual mite control measures including encasement of mattress and pillows with vinyl covers. METHODS: A randomized controlled trial was carried out in 26 homes (14 control versus 12 treatment) of asthmatic patients in two cities (Vancouver and Winnipeg). The control group had the usual house dust mite control measures including the use of vinyl covers for mattresses and pillows while the treatment group had application of benzyl benzoate to mattresses and carpets in the bedroom and the most commonly used room, in addition to the above control measures. Mite allergen levels were measured 3 months and immediately before, 1 week, and 1 and 3 months after the application of house dust mite control measures. Patients kept diary cards on asthma symptoms and peak expiratory flow rates morning and evening one month before and three months after the onset of mite allergen control measures. RESULTS: A reduction of mite allergen level was found in mattress samples in both groups, statistically significant at all times in the treatment group and at one and three months in the control group. Mite allergen levels on floor carpets also showed progressive reduction in both groups, but were significantly different in the treatment group (compared with controls) at 1 week, and were lower compared with baseline in the treatment group up to 3 months. No significant changes in asthma symptoms, peak expiratory flow rates, spirometric measurements, or bronchial hyperresponsiveness were observed among treatment or control group subjects. CONCLUSION: The addition of benzyl benzoate to conventional house dust mite control measures resulted in a significant reduction in floor carpet dust mite levels that persisted for 3 months. The results of this study should be confirmed in a larger and longer study.

Adult↗
PubMed2002

Effect of acaricide resistance on reproductive ability of the honey bee mite Varroa destructor.

The reproduction of pyrethroid-resistant Varroa destructor mite, a brood parasite of honey bees, was observed in Weslaco, Texas, and the results compared with known susceptible mite populations from other studies. Seven Apis mellifera colonies that had mite populations resistant to the acaricide Apistan were used. Pyrethroid-resistance was confirmed when only 17% rather than 90% of mites confined in dishes containing Apistan died after 12 h of exposure. The average number of eggs laid by resistant mites invading worker and drone cells was 4.4 and 5.4 respectively. This is similar to the number of eggs laid by susceptible mites in worker (4.4-4.8) or drone (4.7-5.5) cells. Also the average number of fertilised V. destructor female mites produced by resistant mites in worker (1.0) and drone (2.1) cells were similar to the number produced by susceptible mites in worker (0.9) and drone (1.9-2.2) cells. In addition, no major differences between the resistant and susceptible mite populations were observed in either worker or drone cells when six different reproductive categories and offspring mortality rates were compared. Therefore, it appears that there is little or no reproductive fitness cost associated with pyrethroid resistance in V. destructor in Texas.

Animals↗
PubMed2004

Recapture of male and female dragonflies in relation to parasitism by mites, time of season, wing length and wing cell symmetry.

For aquatic mites parasitic on dragonflies, completion of their life cycle depends on their being returned to appropriate water bodies by their hosts, after completion of engorgement. We examined whether differences among hosts in timing of emergence or phenotypic attributes might affect their probability of return to an emergence pond, and hence success of mites. Parasitized males and females of the dragonfly Sympetrum obtrusum (Hagen) did not differ in overall recapture rates. Females that had wing cell symmetry and emerged early were more likely to be recaptured than females that emerged later or had wing cell asymmetry, but there were no consistent relations between these variables and parasitism by mites. No such relations between wing cell asymmetry, emergence date, and recapture likelihood were found for males. Using randomization tests, we found that mean intensities of Arrenurus planus (Marshall) mites at host emergence were the same for recaptured females and females not recaptured; however, males that were recaptured had lower mean intensities of mites at emergence than males not recaptured. Further, mature females carried more mites than mature males, and the latter had fewer mites than newlyemerged males not recaptured. Biases in detachment of engorging mites do not explain the differences in parasitism between mature males and females, nor the differences in mite numbers between mature males and newly emerged males that were not recaptured. Rather, heavily parasitized males appear to disperse or die and are not recaptured, which should have implications for dispersal of mites and fitness of male hosts.

Animals↗
PubMed1999

Complete mattress encasing is not superior to partial encasing in the reduction of mite allergen.

BACKGROUND: Partial mattress encasing was found to be effective in reducing exposure to mite allergen in our previous investigation. We aimed to compare the short-term efficacy of partial and complete mattress encasing and to study mite-allergen levels within these mattresses. METHODS: Thirty-one mattresses with high mite-allergen content were selected and were randomized into one of three study groups (10 for the control group [CG], 11 for the partial encasing group [PE], and 10 for the complete encasing group [CE]). A special mite-impermeable membrane was used. In the PE group, mattresses were encased on tops and sides only, whereas complete mattress encasement was undertaken in the CE group. Regular bedsheets were applied to all groups. Dust samples were collected over bedsheets at baseline and at months 3 and 6, and over mattresses at baseline and at the end of the study. Group I mite allergens in these samples were measured and compared. RESULTS: At baseline, mattress mite allergens were similar in all groups (P=0.84). Mite allergen at the surfaces of bedsheets (over membranes) from both encasing groups were significantly reduced as compared to the CG group (P=0.003). Such reduction was maintained throughout the 6-month study. At the end of the study, mite antigens within mattresses in the CG and CE groups were increased as compared to baselines, whereas a decrease was observed in the PE group. Significant difference was observed only between the CG and PE groups (P=0.006). CONCLUSIONS: Mattress encasing with a special membrane in this study was highly efficacious in the reduction of mite allergen (>90%). However, with complete encasing, mite allergens within mattresses were increased at the end of the study. Complete mattress encasing in a tropical environment does not offer any advantage over partial encasing.

Allergens↗
PubMed2001

Predictors of house-dust-mite allergen concentrations in dry regions in Australia.

BACKGROUND: House-dust-mite allergen content differs between houses and is thought to be a function of the housing characteristics and furnishing choices that affect indoor microclimate and mite proliferation. The importance of these features may differ with regional climates. METHODS: Concentrations of mite allergen were analysed as a function of housing features. Information on housing features was collected by questionnaire in 50 houses in two towns in a dry inland region of Australia. Mite allergen (Der p 1) was measured by ELISA in dust samples collected on five occasions over 2 years from beds and floors. RESULTS: Der p 1 was detected in all houses. Many housing features did not influence mite allergen concentrations. However, the presence of evaporative cooling increased mite allergen by 3.34-fold in beds (P=0.007) and 3.94-fold in floors (P=0.003). Mite allergen was threefold higher in mattresses >5 years old, and synthetic and feather duvets tended to have higher and lower levels of mite allergen, respectively. CONCLUSIONS: In houses in dry, inland regions of Australia, evaporative cooling and older mattresses are associated with higher concentrations of mite allergen. Alternative forms of air conditioning to evaporative cooling may be useful for control of mite allergen in dry regions.

Allergens↗
PubMed1999

Monitoring the susceptibility of citrus rust mite (Acari: Eriophyidae) populations to abamectin.

A citrus leaf disk bioassay was developed to monitor the susceptibility of citrus rust mite, Phyllocoptruta oleivora (Ashmead), populations to abamectin. Disks from leaves of several citrus cultivars were equally suitable bioassay substrates, and there was no difference in mortality when mites were sprayed directly or exposed to dry abamectin residue. The concentration-response relationship was determined at intervals over 2 yr for a reference population of citrus rust mites that had been maintained in culture and never exposed to acaricides. Three diagnostic concentrations of abamectin were selected based on the response of the reference population and were used to test the susceptibility of 15 populations of mites from commercial citrus groves. Comparisons with the reference population showed reduced levels of susceptibility in some populations. Populations of citrus rust mites from 6 commercial groves were sprayed twice in 1997 with combinations of acaricides designed to exert different intensities of selection pressure from abamectin. None of these populations showed a change in their response to abamectin in pre- and postspray bioassays, although their susceptibility was usually less than that of mites from the susceptible reference population. Biweekly counts of rust mites on fruit in these 6 groves suggested that, relative to groves which received no abamectin or 1 abamectin spray, mite control was not adversely affected in the groves sprayed twice with abamectin. The bioassay method is discussed in relation to factors that affect the interpretation of results from its use, and factors that may affect the development of resistance to abamectin in citrus rust mite populations are presented. This study has provided baseline data with which the results of ongoing tests of the response of citrus rust mite populations to abamectin can be compared.

Animals↗
PubMed2004

Mites and fungi in heavily infested stores in the Czech Republic.

Toxigenic and allergen-producing fungi represent a serious hazard to human food and animal feed safety. Ninety-four fungal species were isolated from mite-infested samples of seeds taken from Czech seed stores. Fungi were isolated from the surface of four kinds of seeds (wheat, poppy, lettuce, and mustard) and from the gut and external surface of five species of mites (i.e., Acarus siro L., 1758, Caloglyphus rhizoglyphoides (Zachvatkin, 1973), Lepidoglyphus destructor (Schrank, 1781), Tyrophagus putrescentnae (Schrank, 1781) and Cheyletus malaccensis Oudemans 1903) separately. Multivariate analysis of fungi complex composition showed that the frequency of fungal was species significantly influenced by the kind of seed. Fungal frequencies differed between mites gut and exoskeleton surface and between the surfaces of mites and seeds. Three groups of fungal species were recognized: 1) mite surface-associated fungi: Penicillium brevicompactum, Alternaria alternata, and Aspergillus versicolor; 2) mite surface- and seed-associated fungi: Aspergillus niger, Penicillium crustosum, Penicillium aurantiogriseum, Penicillium chrysogenum, and Aspergillus flavus; and 3) seed-associated fungi: Cladosporium herbarum, Mucor dimorphosporus f. dimorphosporus, Botrytis cinerea, Penicillium griseofulvum, and Eurotium repens. Mite-carried species of microfungi are known to produce serious mycotoxins (e.g., aflatoxin B1, cyclopiazonic acid, sterigmatocystin, ochratoxin A, and nephrotoxic glycopeptides) as well as allergen producers (e.g., A. alternata and P. brevicompactum). Storage mites may play an important role in the spread of some medically hazardous micromycetes. In addition, these mite-fungi associations may heighten the risk of occurrence of mycotoxins in food and feed stuffs and cause mixed contamination by fungal and mite allergens.

Alternaria↗