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.     

Mites as Selective Fungal Carriers in Stored Grain Habitats

Mites are well documented as vectors of micromycetes in stored products. Since their vectoring capacity is low due to their small size, they can be serious vectors only where there is selective transfer of a high load of specific fungal species. Therefore the aim of our work was to find out whether the transfer of fungi is selective. Four kinds of stored seeds (wheat, poppy, lettuce, mustard) infested by storage mites were subjected to mycological analysis. We compared the spectrum of micromycete species isolated from different species of mites (Acarus siro, Lepidoglyphus destructor, Tyrophagus putrescentiae, Caloglyphus rhizoglyphoides and Cheyletus malaccensis) and various kinds of stored seeds. Fungi were separately isolated from (a) the surface of mites, (b) the mites' digestive tract (= faeces), and (c) stored seeds and were then cultivated and determined. The fungal transport via mites is selective. This conclusion is supported by (i) lower numbers of isolated fungal species from mites than from seeds; (ii) lower Shannon–Weaver diversity index in the fungal communities isolated from mites than from seeds; (iii) significant effect of mites/seeds as environmental variables on fungal presence in a redundancy analysis (RDA); (iv) differences in composition of isolated fungi between mite species shown by RDA. The results of our work support the hypothesis that mite–fungal interactions are dependent on mite species. The fungi attractive to mites seem to be dispersed more than others. The selectivity of fungal transport via mites enhances their pest importance.     

The importance of starch and sucrose digestion in nutritive biology of synanthropic acaridid mites: α‐Amylases and α‐glucosidases are suitable targets for inhibitor‐based strategies of mite control

The adaptation of nine species of mites that infest stored products for starch utilization was tested by (1) enzymatic analysis using feces and whole mite extracts, (2) biotests, and (3) inhibition experiments. Acarus siro, Aleuroglyphus ovatus, and Tyroborus lini were associated with the starch‐type substrates and maltose, with higher enzymatic activities observed in whole mite extracts. Lepidoglyphus destructor was associated with the same substrates but had higher activities in feces. Dermatophagoides farinae, Chortoglyphus arcuatus, and Caloglyphus redickorzevi were associated with sucrose. Tyrophagus putrescentiae and Carpoglyphus lactis had low or intermediate enzymatic activity on the tested substrates. Biotests on starch additive diets showed accelerated growth of species associated with the starch‐type substrates. The inhibitor acarbose suppressed starch hydrolysis and growth of the mites. We suggest that the species with higher starch hydrolytic activity in feces were more tolerant to acarbose, and α‐amylase and α‐glucosidase of synanthropic mites are suitable targets for inhibitor‐based strategies of mite control. © 2009 Wiley Periodicals, Inc.     

Effectiveness of the BT mite trap for detecting the storage mite pests, Acarus siro, Lepidoglyphus destructor and Tyrophagus longior

Traps have been used extensively to provide early warning of hidden pest infestations. To date, however, there is only one type of trap on the market in the U.K. for storage mites, namely the BT mite trap, or monitor. Laboratory studies have shown that under the test conditions (20 °C, 65% RH) the BT trap is effective at detecting mites for at least 10 days for all three species tested: Lepidoglyphus destructor, Tyrophagus longior and Acarus siro. Further tests showed that all three species reached a trap at a distance of approximately 80 cm in a 24 h period. In experiments using 100 mites of each species, and regardless of either temperature (15 or 20 °C) or relative humidity (65 or 80% RH), the most abundant species in the traps was T. longior, followed by A. siro then L. destructor. Trap catches were highest at 20 °C and 65% RH. Temperature had a greater effect on mite numbers than humidity. Tests using different densities of each mite species showed that the number of L. destructor found in/on the trap was significantly reduced when either of the other two species was dominant. It would appear that there is an interaction between L. destructor and the other two mite species which affects relative numbers found within the trap.The British Crowns right to retain a non-exclusive, royalty-free licence in and to any copyright is acknowledged.This revised version was published online in May 2005 with a corrected cover date.     

Mites associated with stored products in Greece

A faunistic survey of mites was conducted in many product stores during a 6-year study period, 2000–2005, in Greece. A total of 1,073 samples were taken from 34 Greek counties. The survey was carried out on grains (wheat, maize, oat, barley), flour, bran, manufactured agricultural foodstuffs, dried fruits (figs, raisins), residues and dust, stored in varying quantities in five types of storage facilities (stores of agricultural cooperative unions, farm stores, commercial stores, flour mills and silos). Dominance-frequency analysis and redundancy analysis (RDA) were used to reveal the preferences of the collected taxa. Approximately 55% of the samples contained mites and 65 mite taxa were identified, belonging to 15 families in four orders. Six species, namely, Acarus gracilis Hughes, A. immobilis Griffiths, Caloglyphus oudemansi (Zachvatkin), Suidasia medanensis Oudemans, Tyrophagus perniciosus Zachvatkin and Kleemania plumigera (Oudemans), were new to the fauna of Greece. Five species, Tyrophagus similis Volgin, Blattisocius mali (Oudemans), Neoseiulus barkeri (Hughes), Cheyletus cacahuamilpensis Baker and Storchia robustus (Berlese), were recorded for the first time in stored products in Greece. Lepidoglyphus destructor (Schrank), Tyrophagus putrescentiae (Schrank) and Acarus siro L. were dominant or intermediate in all storage facilities examined. Cheyletus malaccensis Oudemans was the most common predatory mite. The highest percentage of infestation (65.3) was recorded in the samples from stores of agricultural cooperative unions. Residue-type materials had the highest degrees and percentages of infestation.     

Population dynamics of stored-product mites

Summary Population fluctuation patterns were determined during 1959–70 in wheat bulks in 2 granaries typical of those used on Manitoba farms for 7 kinds of mites. The patterns were bradly similar in the 2 granaries. Outbreaks of all mites except Tarsonemus granarius and Aëroglyphus robustus were unaffected by the prolonged storage of grain; those of Acarus siro and Cheyletus eruditus occurred in unusually high numbers periodically every 2–5 years, whereas Glycyphagus destructor and Androlaelaps casalis were present in relatively low numbers from the first year of storage. A rise in T. granarius population corresponded with grain age and the succession of microfloral species. Tydeid mites occurred periodically.Pricipal component analyses of up to 26 variates including various fungal species on one grain bulk ecosystem provided a kaleidoscopic view of interrelations and dynamics of acarine populations in the grain bulks. The combination of correlated variates of which mites are a part, varied from year to year.Four factors that regulate acarine numbers, particularly those of A. siro and its natural predator C. eruditus, were identified. These are: (i) basic determinants (moisture, temperature, food, and the intrinsic rate of increase of the species); (ii) the main regulator (temperature); (iii) influencers (seed cracks, microflora, dockage, etc.); and (iv) seasonal and cyclic regulators (seasonality in temperature and several density-dependent factors). Generalized diagrams of prey-predator interactions and multivariate interrelations of each kind of mite are presented.Contribution no. 568 from Research Station, Agriculture Canada, Winnipeg, Canada. Invitation paper presented by the first author at the Joint Annual Meeting of the Entomological Societies of America, Canada, and Quebec, Montreal, Quebec, on 26 November 1972     

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.     

Efficacy assessment of soft and hard acaricides against Varroa destructor mite infesting honey bee (Apis mellifera) colonies,through sugar roll method

The parasitic mite Varroa destructor is amongst the most serious problems of honey bees, Apis mellifera (Hymenoptera: Apidae) around the world including Pakistan. The present study estimates the mite density through powdered sugar roll method and evaluates the effectiveness of five miticides (fluvalinate, flumethrin, amitraz, formic acid, and oxalic acid) on A. mellifera colonies in German modified beehives. The results indicated that by treating the bees with one strip and two strips of fluvalinate per colony; the mite population remained below the economic threshold level (ETL) for 14 days and 25 days, respectively. Treatment of flumthrin @1 strip and @ 2 strips per colony resulted in mite population suppressed for 14 days and 39 days, respectively below ETL. Application of Amitraz @ 2 mL per 1.5 L water after every three days interval on sealed brood effectively controlled mites below ETL for 21 days. Formic acid @10 mL per colony applied through plastic applicator proved effective (below 3 mites per bee sample) for 24 days and oxalic acid applied through shop towel method resulted in mite population control for fifteen days. Use of powdered sugar roll method for easy sampling of Varroa mites and application of acaricides on precise economic threshold level during different seasons of the year for integrated management of Varroa mite is hereby advocated by current studies.     

Mite species identification in the production of allergenic extracts for clinical use and in environmental samples by ribosomal DNA amplification

The identification of allergy‐causing mites is conventionally based on morphological characters. However, molecular taxonomy using ribosomal DNA (rDNA) may be particularly useful in the analysis of mite cultures and purified mite fractions in the production of allergenic extracts. Full‐length internal transcribed spacers (ITS1 and ITS2) were obtained from Dermatophagoides farinae, Dermatophagoides pteronyssinus, Dermatophagoides microceras and Euroglyphus maynei (Astigmata: Pyroglyphidae), Glycyphagus domesticus and Lepidoglyphus destructor (Astigmata: Glycyphagidae), Tyrophagus fanetzhangorum, Tyrophagus putrescentiae, Tyrophagus longior, Tyrophagus neiswanderi, Acarus farris and Acarus siro (Astigmata: Acaridae), and Blomia tropicalis (Astigmata: Echymopodidae), using mite‐specific primers. Polymerase chain reaction (PCR) products were digested with HpaII and RsaI restriction enzymes in order to produce species‐specific PCR restricted fragment length polymorphism (RFLP) profiles. A semi‐nested re‐amplification step was introduced before the RFLP in order to apply the method to environmental samples. Results demonstrate that rDNA sequences can be used for the unambiguous identification of mite species. The PCR–RFLP system allows the identification of species in purified mite fractions when the availability of intact adult mite bodies for morphological identification is limited. This reliable and straightforward PCR–RFLP system and the rDNA sequences obtained can be of use in the identification of allergy‐causing mite species.     

Host plant species and carbohydrate supplements affecting rate of multiplication of redlegged earth mite

The effects of young plants of different legume species on the rate of multiplication of Halotydeus destructor (Tucker)(Acarina: Penthaleidae) were examined in one, two or four week experiments in the laboratory. Rates of multiplication of H. destructor were substantially greater on Vicia sativa (common vetch), Phaseolus vulgaris (dwarf bean) and Pisum sativum (snow pea), than on subterranean clover, Trifolium subterraneum; cultivars Dalkeith, Geraldton and Junee. Levels of soluble carbohydrate and soluble nitrogen were greater in vetch, bean and pea, than in the subclovers. Concentrations of 20 amino acids were not associated with differences in mite performance; pea contained higher levels of glutamine and homoserine than the other plants, which may have adversely affected mite multiplication.In further experiments a carbohydrate supplement caused a fourfold increase in rate of multiplication on subclover cv Junee, but had no effect on rate of multiplication on vetch cv Blanchefleur. The carbohydrate supplement did not cause the rate of multiplication on subclover to equal that on vetch. Subclover is not an optimum host plant for H. destructor nutritionally. The nutritional value of host plants is one factor affecting mite multiplication.     

Feeding Life Style of Redlegged Earth Mite, Halotydeus Destructor (Acari: Penthaleidae), in pastures and the role of broad-leafed weeds

Redlegged earth mite, Halotydeus destructor, is a major pest of pastures and crops in Australia, and also feeds on lower plants on the soil surface. Feeding behaviour is reviewed, and the role of Arctotheca calendula, capeweed, in determining occurrence and abundance in pastures is investigated. Mites fed more and produced more progeny on Trifolium subterraneum (subclover) than on capeweed in non-choice experiments. In pastures with mixed species three times more mites were feeding on subclover than on capeweed foliage. However, twice as many mites were found on the soil surface under pasture patches consisting mainly of capeweed than of subclover. Patches were selected on the basis of pasture height, irrespective of plant composition. Twice as many mites were found in populations under patches of tall than short pasture. The daytime relative humidity was higher in tall than short patches, and the temperature slightly lower, making tall patches a more favourable niche for these mites. Ninety per cent of H. destructor were on the soil surface, while 10% were feeding on the upper canopy of pasture. The proportion of each population that was feeding was greater on subclover than capeweed, and subclover was a more suitable food. In Australia H. destructor occurs in regions with mixed pasture species, grown in rotation with grain crops. The ability of H. destructor to utilize foliage of a range of plant species of differing suitability for food, while living mostly on the soil surface in niches favourable for survival, has enabled it to become very abundant.     

Seasonal prevalence of allergenic mites in house dust of Kolkata Metropolis,India

During the past few decades, house dust mites have attracted worldwide interest among medical entomologists and acarologists because of their importance in causing nasobronchial allergic disorders in human beings. House dust mites are present throughout the year; however, their relative densities differ in different seasons and habitats. Because the prevalence of house dust mite allergen is important epidemiologically and clinically, detailed knowledge on the seasonal abundance of important allergenic mites is of great importance for better understanding of the pathogenesis of the disease. In view of this, a systematic survey was carried out on the prevalence of total mites and four common allergenic mites in the city of Kolkata for two consecutive years. Both bed and bedroom floor dust were collected separately from homes inhabited by asthmatic patients situated in different corners of the city on monthly basis from January 2004 to December 2005. The population levels of total mites and four common allergenic mites, namely Dermatophagoides pteronyssinus, D. farinae, Austroglycyphagus geniculatus, and Blomia tropicalis separately, were highest during the pre-monsoon period (March–May), irrespective of habitat, whereas densities were low in all cases during winter (December–February). The study indicates that season had the most significant effect on the relative abundance of house dust mites except Dermatophagoides farinae, irrespective of habitat.     

Deformed wing virus associated with <Emphasis Type="Italic">Tropilaelaps mercedesae</Emphasis> infesting European honey bees (<Emphasis Type="Italic">Apis mellifera</Emphasis>)

Mites in the genus Tropilaelaps (Acari: Laelapidae) are ectoparasites of the brood of honey bees (Apis spp.). Different Tropilaelaps subspecies were originally described from Apis dorsata, but a host switch occurred to the Western honey bee, Apis mellifera, for which infestations can rapidly lead to colony death. Tropilaelaps is hence considered more dangerous to A. mellifera than the parasitic mite Varroa destructor. Honey bees are also infected by many different viruses, some of them associated with and vectored by V. destructor. In recent years, deformed wing virus (DWV) has become the most prevalent virus infection in honey bees associated with V. destructor. DWV is distributed world-wide, and found wherever the Varroa mite is found, although low levels of the virus can also be found in Varroa free colonies. The Varroa mite transmits viral particles when feeding on the haemolymph of pupae or adult bees. Both the Tropilaelaps mite and the Varroa mite feed on honey bee brood, but no observations of DWV in Tropilaelaps have so far been reported. In this study, quantitative real-time RT-PCR was used to show the presence of DWV in infested brood and Tropilaelaps mercedesae mites collected in China, and to demonstrate a close quantitative association between mite-infested pupae of A. mellifera and DWV infections. Phylogenetic analysis of the DWV sequences recovered from matching pupae and mites revealed considerable DWV sequence heterogeneity and polymorphism. These polymorphisms appeared to be associated with the individual brood cell, rather than with a particular host.     

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. This revised version was published online in July 2006 with corrections to the Cover Date.     

Genes important for survival or reproduction in Varroa destructor identified by RNAi

The Varroa mite,(Varroa destructor),is the worst threat to honey bee health worldwide.To explore the possibility of using RNA interference to control this pest, we determined the effects of knocking down various genes on Varroa mite survival and reproduction.Double-stranded RNA (dsRNA)of six candidate genes (Da,Pros26S,RpL8, RpL11,RpPO and RpS13)were synthesized and each injected into Varroa mites,then mite survival and reproduction were assessed.Injection of dsRNA for Da (Daughterless)and Pros26S (Gene for proteasome 26S subunit adenosine triphosphatase)caused a significant reduction in mite survival,with 3.57%±1.94% and 30.03%±11.43% mites surviving at 72 h post-inj ection (hpi),respectively.Control mites injected with green fluorescent protein (GFP)-dsRNA showed survival rates of 81.95%±5.03% and 82.36 ±2.81%,respectively. Injections of dsRNA for four other genes (RpL8,RpL11,RpPO and RpS13)did not affect survival significantly,enabling us to assess their effect on Varroa mite reproduction.The number of female offspring per mite was significantly reduced for mites injected with dsRNA of each of these four genes compared to their GFP-dsRNA controls.Knockdown of the target genes was verified by real-time polymerase chain reaction for two genes important for reproduction (RpL8,RpL11)and one gene important for survival (Pros26S). In conclusion,through RNA interference,we have discovered two genes important for mite survival and four genes important for mite reproduction.These genes could be explored as possible targets for the control of Varroa destructor in the future.     

A laboratory evaluation of a regulated airflow through wheat at four combinations of temperature and humidity on the productivity of three species of stored product mites

Aeration is a promising alternative to the use of pesticides for the control of storage insects by cooling bulk grain, but its effectiveness against mite pests is neither fully understood nor optimised. For this reason, the productivity of three species of storage mites, Acarus siro, Lepidoglyphus destructor and Tyrophagus longior, was studied in a laboratory-based experiment at four combinations of temperature and humidity (10°C and 70% RH, 10°C and 80% RH, 20°C and 70% RH, 20°C and 80% RH) with and without an airflow (at 10 m³/h/tonne, equalling 2.5 l/s/tonne, in tubes containing 15 g of grain). This is the first time that a study has examined the three principal components of aeration separately from each other. The effect of these factors was different for each species. For A. siro, temperature was the most important factor, while airflow and humidity were of similar but lesser importance. For T. longior, temperature was more important than humidity, while the reverse was true for L. destructor. For these two species, airflow was the least important factor. The airflow decreased the productivity of L. destructor and T. longior but increased the productivity of A. siro. This increase in productivity confirms that, in practice, prevention of mite infestations, in particular A. siro, will require storage of grain at low temperature, relative humidity and moisture content. This revised version was published online in July 2006 with corrections to the Cover Date.     

An improved method for rearing Halotydeus destructor (Acari: Penthaleidae) in the laboratory

We developed an improved method for rearing Halotydeus destructor in the laboratory. Mite numbers increased rapidly over the summer of 1992–1993 when fed on vetch, Vicia sativa cv Blanchefleur; in contrast mite numbers were low and fell over the second half of the summer of 1990–91 when fed on subterranean clover, Trifolium subterraneum cv Junee. On V. sativa at a fluctuating temperature from 11 to 18°C 200 mites produced a mean of 1308 and 1455 progeny per transfer in 2 years, a 6–7-fold rate of increase per transfer. The mean transfer time was 35 days and using the interval between transfers as a measure of generation time, the mites completed six to seven generations with no evidence for development of diapause eggs from August until April. There was considerable variability in the numbers of mites produced per pot, associated in part with the presence of Verticillium sp. fungus in 35% of the pots during transfers. Improvement in H. destructor rearing resulted from the use of V. sativa cv Blanchefleur as a food source, maintenance of high humidity and adequate ventilation within cages, and the transfer of mites to fresh food sources at early nymphal stages, which reduced the spread of fungal infections.     

Toxicity and efficacy of selected pesticides and new acaricides to stored product mites (Acari: Acaridida)

Stored product mites can often infest stored products, but currently there is little information regarding the efficacy of pesticides that can be used for control. In this study we evaluated several common pesticides formulated from single active ingredients (a.i.) or commercially available mixtures (chlorpyrifos, deltamethrin, beta-cyfluthrin, and a combination of deltamethrin and S-bioallethrin), plus an acaricide composed of permethrin, pyriproxyfen and benzyl benzolate, for efficacy against Acarus siro, Tyrophagus putrescentiae, and Aleuroglyphus ovatus. The pesticides were incorporated into the mite diets in a dose range of 10–1000 μg a.i. g⁻¹ diet. Concentrations for suppression of 50 and 90% population growth and eradication (rC₀) of mites were fit to linear regression models. None of the tested pesticides gave complete eradication of A. siro, which was the most tolerant of the three mite species tested. The most effective pesticide Allergoff 175 CS was a combination product (a nano-capsule suspension of permethrin, pyriproxyfen and benzyl benzolate) labeled for dust mites, with rC₀ range of 463–2453 μg a.i. (permethrin) g⁻¹ diet depending on the species. Least effective were chlorpyrifos and deltamethrin.     

The occurrence of mites in cereal-based foods destined for human consumption and possible consequences of infestation

Seven categories of cereal-based food products purchased at food retail outlets in UK were examined for the presence of mites by analysing 20g samples using a flotation method. Mites were found in 21% of 571 samples, which were examined soon after purchase, and in 38% of 421 samples, derived from the 571 samples which were examined after 6 weeks of storage in volunteers' homes. Most of the samples where mites were detected had fewer than five mites. However, a few samples contained more than 20 mites with a maximum of 428 mites detected in a single sample. Sixteen families, genera or species of mites were recovered. The most common species were Acarus siro, Tyrophagus putrescentiae, Lepidoglyphus destructor and Glycyphagus domesticus. The level of contamination was broadly similar for each of the seven categories of products examined. It is likely that infestation occurs at every stage of food processing and storage. This is the first study of its kind and there is no reason to believe that results from similar studies carried out in other temperate countries would be markedly different. Increase in the percentage of contaminated samples following storage in a domestic situation suggests that the domestic environment is an important factor in developing infestation. The implications of mite contamination on food quality and on human health are briefly discussed.     

Cold storage of Halotydeus destructor (Acari: Penthaleidae) for use in experiments

Survival of medium sized nymphal stages of redlegged earth mite Halotydeus destructor (Tucker) (mainly tritonymphs and deutonymphs) stored under low temperature (1.5°C) in sealed plastic boxes remained more than 50% after 12 days of storage, with some mites surviving for up to eight weeks. Adding fresh subclover leaves into the storage box increased the survival rate of mites from 12% to 28%, 19 days after the storage started. Mites stored for two weeks at low temperatures showed feeding activity in a screening experiment similar to mites collected directly from the field. This indicated that cold storage of redlegged earth mite can be used to build up mite numbers for large screening experiments, or to extend the period of availability of mites collected from the field. However, their reproductive ability was greatly reduced after three weeks at low temperature. Thus, care should be taken when using mites for experiments measuring reproduction. The implications of low temperatures for reducing field populations of mites in midwinter are also discussed.