Differential levels of mite infestation of wheat and barley in Czech grain stores

Abstract  While mites are able to utilize numerous food sources, the suitability of the food strongly influences population growth. The different suitabilities of various stored agricultural products will thus affect the level of infestation. In this study, we compared field mite infestation rates in two stored cereals: wheat and barley. We analyzed mite abundance, frequency and species composition in samples of grain obtained from 79 selected Czech grain stores. Stored barley seemed to be more vulnerable to mite attack than wheat, as we consistently found more infested samples, more species and higher mean and median mite abundance per sample in barley as compared to wheat. The mean mite abundance per sample were 55 and 506 individuals for wheat and barley, respectively. In barley, 10% of samples exceeded allergen risk threshold (i.e., 1 000 individuals per kg of grain). Altogether, 25 species were identified from approximately 35 000 individuals. The most frequently identified species were the same in wheat and barley, that is, Tydeus interruptus Sig Thor, Acarus siro L., Tarsonemus granarius Lindquist, Lepidoglyphus destructor (Schrank) and Tyrophagus putrescentiae (Schrank). Based on principal components analysis, we found a closer association of T. interruptus , T. putrescentiae , L. destructor and Cheyletus eruditus (Schrank) with barley samples, corresponding to the high frequency and abundance values of these mites. The probable reasons for the higher infestation, especially mite abundance in barley, are discussed in relation to the higher proportion of crushed parts, which may release favorable nutrient sources and amplify the abundance values.     

The susceptibility of different strains of Cheyletus eruditus (Acarina: Cheyletidae) to organophosphate acaricides

The acaricide susceptibility of seven strains of Cheyletus eruditus, originating from field populations of different sources, such as grain stores, a chaff pile and pheasant fodders, was compared with that of two laboratory strains. The strain least susceptible to all the organophosphates tested was the one that survived fumigation by PH3. The laboratory strains and a strain from Denmark were the most susceptible. The use of the population of C. eruditus with the lowest susceptibility to organophosphates is desired in the management of acaroid mites. It is intended that mites of this strain will be mass reared and used for dissemination in grain stores for the biological control of acaroid mites.     

Spatiotemporal distribution of insects and mites in horizontally stored wheat

Samples were taken from a flat storage facility located in central Greece, filled with approximately 45 tons of hard wheat, to assess the spatiotemporal distribution of stored-product insects and mites. The wheat was stored in a 1.5-m-deep bulk from June 2001 until March 2002. The samples were taken with a partitioned grain trier during the entire storage period, at 10-d intervals. The trier samples were examined separately for the upper, medial, and lower 0.5 m of the bulk. The spatial distribution of the insect and mite species found was examined by contour analysis based on the numbers of individuals in the trier samples. Nine insect and 20 mite taxa were found during the sampling period. The most abundant insect species were Tribolium castaneum (Herbst), Cryptolestes ferrugineus (Stephens), and Rhyzopertha dominica (F.); the most abundant mite species were Lepidoglyphus destructor (Schrank), Acarus siro L., and the predator Cheyletus malaccensis Oudemans. The highest population densities for the majority of the insect and mite species were recorded during autumn. The majority of the individuals of the most abundant insect and mite species were found in the upper 0.5 m of the bulk, with the exception of C. malaccensis, which was equally distributed in the upper and medial 0.5 m of the bulk. The spatiotemporal distribution during the entire experimental period was notably varied according to the insect and mite species.     

Rapid method for the detection of storage mites in cereals: feasibility of an ELISA based approach

This paper describes the development of rapid immunodiagnostic tests for the detection of storage mite infestations in cereals and cereal products. The study's first phase (proof of concept) involved the production of a species-specific enzyme-linked immunoassay (ELISA) for the flour mite, Acarus siro (L.), a major pest of stored commodities. The specificity of this new assay was assessed against key stored product contaminants (13 species of mites of which three were predatory, five species of insects and five species of fungi) in the presence and absence of grain. The assay was species-specific (no cross-reactivity to other storage contaminants) and was unaffected by the presence of cereal antigens in the extract. In the study's second phase, species- and genera-specific ELISAs were developed for a range of key storage mite pests: the cosmopolitan food mite (Lepidoglyphus destructor), the grocers' itch mite (Glycyphagus domesticus), the grainstack mite (Tyrophagus longior), mites of the Tyrophagus and Glycyphagus generas, and all storage mites. All tests were demonstrably specific to target species or genera, with no cross-reactions observed to other storage pest contaminants or cereals. The final, validation phase, involved a comparative assessment of the species-specific A. siro and the genus-specific Tyrophagus ELISAs with the flotation technique using laboratory and field samples. Both ELISAs were quantitative (0-30 mites per 10 g wheat) and produced good comparative data with the flotation technique (A. siro r(2)=0.91, Tyrophagus spp. r(2)=0.99).     

Molecular and biochemical properties of storage mites (except Blomia species)

In recent years, the allergological importance of different mite species not belonging to the family Pyroglyphidae has been demonstrated. These mites, commonly named storage mites, include Lepidoglyphus destructor, Glycyphagus domesticus, Tyrophagus putrescentiae, Acarus siro, Aleuroglyphus ovatus, Suidasia medanensis and Thyreophagus entomophagus. Several allergens from these species have been purified, sequenced and cloned. Many of these allergens have shown sequence homology and a biological function similar to those previously described in Blomia tropicalis and the Dermatophagoides spp. The main allergens described in storage mites include fatty acid binding proteins, tropomysin and paramyosin homologues, apoliphorine like proteins, alfa-tubulines and other, such as group 2, 5 and 7 allergens, which definitive biological function has not been described yet. Besides the purification and characterization of allergens, the allergenicity of other species such as Acarus farris, Austroglycyphagus malaysiensis, Blomia kulagini and B. tjibodas, Cheyletus eruditus, Chortoglyphus arcuatus, Gohieria fusca, Thyreophagus entomophagus and Tyrophagus longior has been investigated. Research has also been conducted to identify allergens in parasitic mites, such as Psoroptes ovis, Sarcoptes scabiei, Varroa jacobsoni, Diplaegidia columbae and Hemisarcoptes cooremani. The allergenicity of mites present in agricultural environments has been investigated. Crossreactivity studies have also been performed to elucidate to what extent all these mites share common, or species specific epitopes. Herein we present a comprehensive review of the allergenicity of mite species which have been implicated in human respiratory and/or dermatological diseases.     

Suppressive potential of bean (Phaseolus vulgaris) flour against five species of stored-product mites (Acari: Acarididae)

Previous research has demonstrated that legume proteins have insecticidal activity against stored-product pests, but activity against stored-product mites has not been tested. A study was therefore conducted to explore the potential of bean, Phaseolus vulgaris L., flour as novel botanical acaricide against five species of storage and dust mites: Acarus siro L., Aleuroglyphus ovatus (Troupeau), Caloglyphus redickorzevi (Zachvatkin), Lepidoglyphus destructor (Schrank), and Tyrophagus putrescentiae (Schrank). The effect of wheat, Triticum aestivum L., grain enriched with bean flour to eight concentrations (0, 0.01, 0.1, 0.5, 1, 2.5, 5, and 10%) on population growth initiating from the density of 50 mites per 100 g of wheat was recorded for 21 d under laboratory conditions (grain moisture 14.6% moisture content and 25 degree C in darkness). The enrichment of grain with bean flour suppressed the population growth of all tested species: 0.01% concentration reduced population growth of all tested species to >50% in comparison with the control population. The most sensitive species were A. siro and L. destructor, followed by T. putrescentiae and C. redickorzevi. The least sensitive species was A. ovatus. The terminal (i.e., after 21 d) density of mites positively correlated with bean flour concentration. The suppressive effect of bean flour was not linear but rather asymptotic. The results of this study are discussed in the context of the application of bean flour in integrated control of stored-product mites and the elimination of stored-product mite allergens.     

The effectiveness of organophosphate acaricides on stored product mites interacting in biological control

Three organophosphates (pirimiphos-methyl, chlorpyrifos-methyl, chlorpyrifos) were tested on a laboratory strain of Cheyletus eruditus (Schrank), a predatory mite used for biological control of stored food mites, and on tow species of acaroid mites, Acarus siro L. and Tyrophagus putrescentiae (Schrank). Biological control is often preceded by a chemical treatment with organophosphates and thus it is important to know how the acaricides affect the predators. It was found that chlorpyrifos-methyl was the most toxic organophosphate on C. eruditus. The effectiveness of pirimiphos-methyl and chlorpyrifos was approximately equal and was three times lower than the effectiveness of chlorpyrifos-methyl. The organophosphates were nearly equally effective on both acaroid mites but A. siro was slightly more susceptible than T. putrescentiae. On the basis of these results, the use of pirimiphos-methyl or chlorpyrifos rather than chlorpyrifos-methyl is recommended for protection of empty stores or stored grain against resiliant populations of stored food mites.     

Temperature preference and respiration of acaridid mites

The thermal preferences in a grain mass and respiration at various temperatures in mites (Acari: Acarididae) of medical and economical importance [Acarus siro (L. 1758), Dermatophagoides farinae Hughes 1961, Lepidoglyphus destructor (Schrank 1871), and Tyrophagus putrescentiae (Schrank 1781)] were studied under laboratory conditions. Based on the distribution of mites in wheat, Triticum aestivum L., grain along a thermal gradient from 10 to 40 degrees C, L. destructor, D. farinae, and A. siro were classified as eurythermic and T. putrescentiae as stenothermic. The lowest preferred temperature was found for D. farinae (28 degrees C), followed by A. siro (28.5 degrees C), L. destructor (29.5 degrees C), and T. putrescentiae (31.5 degrees C). The relationship between the respiration rate and the temperature was similar for all four mite species. The highest respiration was found in the range from 31 to 33 degrees C. This is approximately 2 degrees C higher than the preferred temperature of these species. The lower temperature threshold of respiration ranged from 1 to 5 degrees C and the upper threshold ranged from 45 to 48 degrees C. Acclimatization of A. siro to temperature regimes of 5, 15, and 35 degrees C resulted in thermal preferences between 9 and 12 degrees C, 9 and 20 degrees C, and 28 and 35 degrees C, respectively. The respiration rate of acclimatized specimens increased with the temperature, reaching a maximum at 29.0 degrees C for mites acclimatized at 5 and 15 degrees C and a maximum at 33.7 degrees C for those acclimatized at 30 degrees C.     

Wheat curl mite (Acari: Eriophyidae) dispersal and its relationship with kernel red streaking in maize

Wheat curl mites, Aceria tosichella Keifer, dispersing from wheat (Triticum spp.) to nearby corn (Zea mays L.) fields play a role in the development of kernel red streaking in corn. These studies were undertaken to verify the relationship of wheat curl mite to kernel red streaking, to determine whether wheat is the main source of curl mites dispersing into corn and to determine whether planting corn in temporal or spatial isolation of wheat is a valid management strategy. These studies were conducted on farm fields using sticky traps to monitor mites, followed by sampling mature grain for kernel streaking in southwestern Ontario from 1999 to 2002. The dominant source mites were winter wheat. Mite dispersal occurred during the first 3 wk of winter wheat maturation after the wheat had reached Zadoks stage 87. Mite dispersal corresponded to prevailing winds in the area with the lowest number of mites and the lowest severity of kernel red streaking occurring 60 m from wheat fields planted to the north, south, and east of cornfields and 90 m from wheat fields planted to the west of cornfields. The severity of kernel red streaking was positively correlated with the density of wheat curl mites in corn; however, the correlation was weak and kernel red streaking was still high in many cornfields when few or no mites were present. These findings suggest that wheat curl mite migration into corn is not entirely predictive of the incidence and severity of kernel red streaking.     

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.     

Comparison of detection methods for Acarus siro (Acari: Acaridida: Acarididae) contamination in grain

Acarus siro L. 1758 (Acari: Acaridida: Acarididae) is an important pest of stored grain because it contaminates the grain by allergens and transfers pathogenous microorganisms. Rapid detection of contamination enables to intercept an early grain infestation by the pest. In this study, we compared the usability and efficiency of various detection approaches. Under laboratory conditions, grain samples of various sizes were infested by different levels of the following contaminants: eggs, adults, and feces of A. siro. The samples were analyzed by enzyme-linked immunosorbent assay (ELISA) by using anti-A. siro polyclonal antibody (immunochemical method), extracted in Berlese-Tullgren funnels, sieved, and processed by filth-flotation (conventional methods). The adults or juveniles of A. siro could be detected by all the three tested conventional methods and ELISA with detection limits in the range from 221 to 1,157 mites/kg grain. Eggs were detected by filth-flotation only; the detection limit was 1,950 eggs/kg grain. The feces of A. siro were detectable by ELISA test, only. ELISA enabled the detection of the feces with the minimal threshold level of 1.04 microg feces/g grain; it means the assay allowed to trace less than one metabolically active mite per gram of grain. The study thus demonstrated that reliable A. siro detection in grain can only be achieved by combining different detection methods. European Union and U.S. administratives dictate zero or near-zero tolerance level for mite infestation in stored products. This demand is difficult to fulfill, because every detection method is limited by its detection limit; thus, it is hard to reliably detect infestation levels lower than obtained detection limits. This methodical limitation is discussed in context with the determined detection limits of the tested methods.     

Bartonella-like bacteria carried by domestic mite species

Bacteria of the genus Bartonella are carried by haematophagous mites, ticks, fleas and flies, and attack the erythrocytes of mammals. Here we describe a Bartonella-like clade, a distinct group related to Bartonellaceae, in stored-product mites (Acari: Astigmata) and a predatory mite Cheyletus eruditus (Acari: Prostigmata) based on the analysis of cloned 16S rRNA gene sequences. By using the clade-specific primers, closely related Bartonella-like 16S rRNA sequences were amplified from both laboratory colonies and field strains of three synanthropic mite species (Acarus siro, Lepidoglyphus destructor and Tyrophagus putrescentiae) and a predatory mite. Altogether, sequences of Bartonella-like bacteria were found in 11 strains, but were not detected in Dermatophagoides farinae and D. pteronyssinus and two strains of L. destructor. All obtained sequences formed a separate cluster branching as a sister group to Bartonellaceae and related to other separate clusters comprising uncultured bacterial clones from human skin and hemipteran insects (Nysius plebeius and Nysius sp.). The classification of sequences into operational taxonomic units (OTUs) showed a difference between A. siro and T. putrescentiae suggesting that the Bartonella-like bacteria are different in these two mite species. However, species specific sequences in separate OTUs were observed also for C. eruditus. Possible symbiotic interactions between Bartonella-like bacteria and their mite hosts are discussed.     

Dynamics and distribution patterns of acarine populations in stored-oat ecosystems

Population dynamics and aggregation patterns of nine kinds of stored-grain mites were studied in two 7.5 tonne lots of hulled (cv. Random) and hulless (cv. Terra) oat cultivars with 12–14% moisture content stored in two wooden bins in Manitoba, Canada during 1978–84. Random oats harbored more mites than Terra oats. Lepidoglyphus destructor Schrank was the most common granivorous mite and Cheyletus eruditus Shrank the most common predatory mite. Ecological data on a tydeid mite, Paratriophtydeus coineaui André, are presented for the first time. Because they were more abundant in Terra oats with higher fat acidity values (FAV) than Random oats with lower FAVs, L. destructor and Tarsonemus granarius Lindquist could be used as bioindicators of spoilage of stored oats. All species analyzed showed some significant difference in their abundance at different depths in the grain bulk; some species showed depthxtime interaction. Aggregation patterns indicated most mite species had overdispersed (clumped) distribution. T. granarius, and Blattisocius keegani Fox-Androlaelaps casalis Berlese had a distinct aggregation pattern in each oat cultivar.     

The effects of temperature and dose of formic acid on treatment efficacy against Varroa destructor (Acari: Varroidae), a parasite of Apis mellifera (Hymenoptera: Apidae)

In order to decrease the variability of formic acid treatments against the honey bee parasite the varroa mite, Varroa destructor, it is necessary to determine the dose-time combination that best controls mites without harming bees. The concentration × time (CT) product is a valuable tool for studying fumigants and how they might perform under various environmental conditions. This laboratory study is an assessment of the efficacy of formic acid against the varroa mite under a range of formic acid concentrations and temperatures. The objectives are 1) to determine the effect of temperature and dose of formic acid on worker honey bee and varroa mite survival, 2) to determine the CT₅₀ products for both honey bees and varroa mites and 3) to determine the best temperature and dose to optimize selectivity of formic acid treatment for control of varroa mites. Worker honey bees and varroa mites were fumigated at 0, 0.01, 0.02, 0.04, 0.08, and 0.16 mg/L at 5, 15, 25, and 35 °C for 12 d. Mite and bee mortality were assessed at regular intervals. Both mite and bee survival were affected by formic acid dose. Doses of 0.08 and 0.16 mg/L were effective at killing mites at all temperatures tested above 5 °C. There was a significant interaction between temperature, dose, and species for the CT₅₀ product. The difference between the CT₅₀ product of bees and mites was significant at only a few temperature-dose combinations. CT product values showed that at most temperatures the greatest fumigation efficiency occurred at lower doses of formic acid. However, the best fumigation efficiency and selectivity combination for treatments occurred at a dose of 0.16 mg/L when the temperature was 35 °C. This revised version was published online in July 2006 with corrections to the Cover Date.     

Comparison of Communities of Stored Product Mites in Grain Mass and Grain Residues in the Czech Republic

In storage facilities one can find grain either in stored grain mass or in grain residues in the store corners or machinery. Although it is claimed that grain residues are serious pest reservoirs since they harbor numbers of stored product arthropods and are connected via continuous emigration with grain mass, the documentation for this is not convincing. Therefore in 78 selected grain stores, we simultaneously sampled the grain mass and residues in order to compare concurrent mite communities in these two different habitats. We found 30 species in about 614 000 individuals in residues and 23 species in about 20 000 individuals in grain mass. Canonical correspondence analysis (CCA) of transformed abundance data showed differences in the communities of mites in grain mass and residues: (i) species associated to grain residues (e.g. Tyrophagus longior, Tydeus interruptus, Acarus farris and Cheyletus eruditus) and (ii) species associated to both grain mass and grain residues (e.g. Tarsonemus granarius, Acarus siro, Tyrophagus putrescentiae, Lepidoglyphus destructor and Cheyletus malaccensis). Although the residue samples had more mites and higher species diversity than the stored grain mass, no correlation in mite abundance and species numbers between samples from grain residues and grain mass was found, thereby indicating low connectivity of these two habitats.     

The effect of modified atmospheres on the survival of the eggs of four storage mite species

The results of a laboratory investigation into the effects of modified atmospheres (MA) on the eggs of mite pests of grain and cheese are presented. Four species of astigmatid mite were tested; Acarus farris (Oudemans). A. siro L., Lepidoglyphus destructor (Schrank) and Tyrophagus longior (Gervais). All are found in many habitats including grain and cheese stores. Three low oxygen (O2) MA mixtures were used, based on carbon dioxide (CO2), nitrogen (N2) or simulated burner gas (0.5 or 2% O2, 10% CO2, balance N2) plus 60% CO2 in air (8% O2). The mites were exposed at 15 degrees C and 80% r.h., a combination of conditions that occurs at the surface of stored grain during the autumn which promotes mite population growth. The exposure periods required to prevent egg hatch for each species in every mixture are given. Tyrophagus longior was the most tolerant species, followed by A. siro and A. farris, with L. destructor the most susceptible. Burner gas was the most effective mixture overall with 0.5% O2 but with an increase in the O2 level to 2% for all the mixtures, CO2 became the more effective control agent. With 60% CO2 in air some loss of efficacy was observed against the three most tolerant species and even more so for L. destructor. Sublethal exposures to MAs for at least 4 days in L. destructor, 6 days in A. farris and A. siro and 8 days for T. longior caused a delay in egg hatch.     

Mites from house dust in Glasgow

Glasgow's mild, high-rainfall climate, combined with a deteriorating quality of housing and low standards of living in many parts of the city, makes it a particularly suitable place for thriving populations of house dust mites. The acarofauna in 124 samples of house dust from beds and carpets in seventy-four homes in Glasgow, Scotland, comprised thirty-one species of which the most abundant were Dermatophagoides pteronyssinus (Trouessart) (64.3%), Glycyphagus domesticus (De Geer) (16.7%), Euroglyphus maynei (Cooreman) (11.6%), Tarsonemus sp. (1.6%), Cheyletus eruditus (Schrank) (1.5%), C. trouessarti Oudemans (0.9%), Tarsonemus fusarii Cooreman (0.8%) and Glycyphagus destructor (Schrank) (0.7%). Mites were present in all the homes surveyed and the mean population density was found to be 97/100 mg of dust (range 2-1210). Over 47% of homes visited showed signs of disrepair associated with damp, especially unmodernized flats in old tenement buildings and 1960s council housing stock, many of which contain deprived occupants. There was a high incidence of hygrophilic species such as Glycyphagus spp., Tarsonemus spp. and Euroglyphus maynei in such homes. Samples from homes of atopic asthmatics were found to contain significantly fewer mites than those from normal volunteers (chi 2 = 54.7). This was partly due to the use of house dust mite avoidance measures (e.g. regular vacuum cleaning of mattresses as well as carpets) by some of the asthmatics.     

Detection and identification of species-specific bacteria associated with synanthropic mites

Internal bacterial communities of synanthropic mites Acarus siro, Dermatophagoides farinae, Lepidoglyphus destructor, and Tyrophagus putrescentiae (Acari: Astigmata) were analyzed by culturing and culture-independent approaches from specimens obtained from laboratory colonies. Homogenates of surface-sterilized mites were used for cultivation on non-selective agar and DNA extraction. Isolated bacteria were identified by sequencing of the 16S rRNA gene. PCR amplified 16S rRNA genes were analyzed by terminal restriction fragment length polymorphism analysis (T-RFLP) and cloning sequencing. Fluorescence in situ hybridization using universal bacterial probes was used for direct bacterial localization. T-RFLP analysis of 16S rRNA gene revealed distinct species-specific bacterial communities. The results were further confirmed by cloning and sequencing (284 clones). L. destructor and D. farinae showed more diverse communities then A. siro and T. putrescentiae. In the cultivated part of the community, the mean CFUs from four mite species ranged from 5.2?×?10(2) to 1.4?×?10(3) per mite. D. farinae had significantly higher CFUs than the other species. Bacteria were located in the digestive and reproductive tract, parenchymatical tissue, and in bacteriocytes. Among the clones, Bartonella-like bacteria occurring in A. siro and T. putresecentiae represented a distinct group related to Bartonellaceae and to Bartonella-like symbionts of ants. The clones of high similarity to Xenorhabdus cabanillasii were found in L. destructor and D. farinae, and one clone related to Photorhabdus temperata in A. siro. Members of Sphingobacteriales cloned from D. farinae and A. siro clustered with the sequences of "Candidatus Cardinium hertigii" and as a separate novel cluster.     

Combined effect of an antifeedant α-amylase inhibitor and a predator Cheyletus malaccensis in controlling the stored-product mite Acarus siro

Abstract.  Acarus siro is the most abundant and frequent mite to infest stored-food products, causing allergies and transmitting mycotoxin producing fungi. The predatory mite Cheyletus malaccensis is a candidate species in the biocontrol programme for this pest. In vitro , the α-amylase inhibitor acarbose is effective against the α-amylase of A. siro but not against that of C. malaccensis . In vivo , the impact of acarbose on a population of A. siro is investigated along with the interaction with the predator. Various densities of adult parthenogenetic females of C. malaccensis are reared on A. siro feeding on either a control diet or a diet containing different acarbose concentrations. The combined action of both factors significantly improved the final biocontrol efficiency with C. malaccensis , compensating for the lower energetic content of the prey on acarbose by increasing the number of prey caught. Acarbose had no negative effects on the longevity and the length of oviposition period of C. malaccensis but partially reduced its fecundity. The results are discussed in the context of the integrated control of stored-product mite pests.     

A new bioassay method for the detection of resistance to pesticides in the stored product mite Acarus siro (Acari: Acaridae)

The majority of bioassay methods used for determining the susceptibility of the flour mite Acarus siro L. to pesticides provide data which are difficult to assess. In this new method, the mites are confined on treated, moulded filter papers held in position by two glass sheets to form an escape-proof exposure chamber. The method is simple and uses materials that are likely to be readily available. The dose–response data obtained from laboratory and field strains of A. siro to three organophosphorus-based pesticides are presented. The method provided repeatable results and no significant variation when used by different operators. A discriminating dose for the detection of pirimiphos-methyl resistance is suggested.