Temperature-dependent population growth of three species of stored product mites (Acari: Acaridida)

The pest potential of stored product mites depends on the reproduction rate that is affected by the environmental conditions. In this study we investigated the effect of temperature, ranging from 5 to 35°C, on the population growth of three important mite species, Acarus siro, Tyrophagus putrescentiae and Auleroglyphus ovatus at 85% r.h. Starting with 10 individuals the population increase of mites was observed after 3 weeks of cultivation, or after 6 weeks for those kept at low temperatures (5, 10, 12.5, and 15°C). The rate of increase was calculated for each temperature and species. The obtained data were fitted with polynomial models. The mite population growth rates increased with increasing moderate temperatures until 25°C, when r _m -values were 0.179, 0.177 and 0.190 for A. siro, A. ovatus and T. putrescentiae, respectively. The lower development threshold was 10.2°C in all three species. Estimated upper temperature threshold was higher in T. putrescentiae (49°C) than in A. siro and A. ovatus (38°C). Simulation of the rate of population increase under ideal conditions, using real temperature records obtained from Czech grain stores, showed that the pest mite populations increase only during 3.5 months within a typical 9-month storage season in Central Europe. These results indicate that control of mites, be it chemical, physical or biological, is recommended during the months when allergens and pests are produced, i.e. from September to mid November and in May.     

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.     

Bulbs mycoflora and their relation with three stored product mites

The distribution of moulds on stored and field onion and garlic plants infested by bulb mites in Assiut area (Egypt) was studied using PDA medium at 28 °C. Among 40 host samples and the three mite species tested no significant difference was noted in the contamination by moulds. A total of 20 species appertaining to 11 genera were identified from the tested mites and their habitats. The predominant moulds on all samples were “storage moulds” from the genera Aspergillus (A. niger, A. versicolor)and Penicillium (P. chrysogenum, P. funiculosum,and ``field moulds' among which Alternaria, Cladosporium,Fusarium (and its teleomorphs) and Setosphaeria were encountered most frequently. One fungus well known facultative pathogen was obtained: Beauveria bassiana. The tested mites transferA. niger, N. haematococca, R. stolonifer andP. chrysogenum outside their bodies while, A. flavusand A. ochraceus transfer through their digestive tracts along with the foods. Individuals of all mites could survived till the end of the experiment on all fungal species tested except A. niger, A. ochraceus and A. sydowii.Among 48 isolates screened for their ability to produce chitinase, about 83% of the isolates could produce this enzyme. Most of the positive isolates (17 isolates) had moderate producers This revised version was published online in June 2006 with corrections to the Cover Date.     

Hide protease in stored product mites (Astigmata:acaridae)

• 1.1. Hide protease activity was detected in 6 species of stored product mites; Acarus siro Linnaeus, Glycyphagus destructor (Schrank), Glycyphagus domesticus (De Geer), Rhizoglyphus callae (Oudemans), Rhizoglyphus robini Claparede and Tyrophagus longior (Gervais).
• 2.2. Significant differences in specific activity were found between, but not within, species.
• 3.3. A. siro L. and Glycyphagus spp. show relatively high activity, Rhizoglyphus spp. and T. longior (Gervais) relatively low activity.
• 4.4. Possible explanations for these results are discussed.

     

Tyroglyphid mites in stored products Methods for the study of population density

The known methods for detecting the presence of tyroglyphids are described. For coarse materials, such as seeds, sieving is recommended. For flour, it is better to examine exposed surfaces, or to keep samples in glass vessels and examine for the runnels made by mites against the glass. Methods of sampling to provide information about the density and extent of infestations are described. Samples must usually be treated in the laboratory. While methods which do not involve the separation of the mites from the material are referred to, such separation is usually necessary. Mites may be separated from most materials by the modified Berlese funnel method of Chernuishev and Petrova; means of overcoming certain disadvantages are suggested. However, vigorous sieving is recommended for coarse materials, and a flotation method, using dichlorethylene, for fine materials such as flour. It is usually more satisfactory to examine and count the mites than to estimate the numbers volumetrically or gravimetrically. They are counted in a dish containing oil, placed on squared paper under a low-power microscope. A modification of this method, for dealing with large numbers, is described. Methods of expressing population density are briefly discussed.     

The effects of physical factors on survival of stored food mites

The effects of physical factors (low barometric pressure, high and low temperature, light) on survival of stored food mites (Acaridae: Acarus siro L., Tyrophagus putrescentiae (Schrank), Aleuroglyphus ovatus (Troupeau), Caloglyphus berlesei (Michael); Glycyphagidae: Glycyphagus domesticus De Geer; Carpoglyphidae: Carpoglyphus lactis (L.); Pyroglyphidae: Dermatophagoides pteronyssinus (Troupeau); Cheyletidae: Cheyletus eruditus (Schrank) were studied. C. lactis was the most resistant species-most specimens (85%) of this species survived the longest exposure (96 h) to the lowest pressure (95 mm Hg) tested. It showed 100% mortality only after 80 h exposure to -15°C and it was able to withstand 45°C for about 1 h. Mites from the family Acaridae were killed by low pressure of 95 mm Hg after an exposure of only 48 h and after 1 h exposure to -15°C. Constant light has unfavourable effects on development and reproduction of the flour mite, A. siro.Our results may have some practical implications. Vacuum of 190 mm Hg will protect the food against the mites. Also low temperature -15°C could be used to control mites in seed.     

The effect of stored barley cultivars, temperature and humidity on population increase of Acarus siro, Lepidoglyphus destructor and Tyrophagus putrescentiae

The rate of population increase of three mite species, Acarus siro (L.), Lepidoglyphus destructor (Schrank) and Tyrophagus putrescentiae (Schrank), was studied on various types of barley and at various combinations of temperature and humidity. The mites were added into the chambers and incubated for 21 days on seven different kinds of barley coming from four sites, including six cultivars and a mixture. The population increase of all species was higher on the mixture than on any other cultivar, except for Sebastian and Calgary. The increase of mites was studied at constant temperatures ranging from 5 to 35 °C and relative humidity (RH) ranging from 50 to 90 %. Positive rate of increase was found above 70 % RH for all species. The optimal humidity was at 85 % RH for A. siro and L. destructor and at 90 % RH for T. putrescentiae. As concerns the temperature, positive rate of increase was found at temperatures higher than 10, 15 and 20 °C for A. siro, L. destructor and T. putrescentiae, respectively. The temperature optima were at 23, 25, and 30 °C for A. siro, L. destructor and T. putrescentiae, respectively. Model estimated on laboratory data was then fitted to temperature and humidity records from August to November in the Czech grain store. Estimated population rate of increase was rarely positive: for A. siro it was for 24 %, for L. destructor for only 1 % and for T. putrescentiae for only 7 % days of the study period. It is concluded that in the climatic conditions of the Czech Republic the population increase of three mite pests is negligible during autumn and winter.     

粉螨污染储藏干果的调查研究

目的调查粉螨污染储藏干果状况及其孳生种类、密度、物种多样性和种群动态。方法从安徽某些城市干果商店(仓库)和中药店(仓库)采集食用干果和药用干果,分离其中的孳生粉螨。结果从60种干果样本中共分离出粉螨18种,隶属于6科16属,其中以甜果螨、家食甜螨、害嗜鳞螨和腐食酪螨为主。结论贮藏干果孳生粉螨种类较多,虫口密度较高,因此,应采取措施控制粉螨孳生以降低粉螨对人类健康的危害。     

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 aldehyde hypothesis: metabolic intermediates as antimicrobial effectors

There are many reactive intermediates found in metabolic pathways. Could these potentially toxic molecules be exploited for an organism''s benefit? We propose that during certain microbial infections, the production of inherently reactive aldehydes by an infected host is a previously unappreciated innate immune defence mechanism. While there has been a significant focus on the effects of aldehydes on mammalian physiology, the idea that they might be exploited or purposefully induced to kill pathogens is new. Given that aldehydes are made as parts of metabolic programmes that accompany immune cell activation by the cytokine interferon-gamma (IFN-γ) during infections, we hypothesize that aldehydes are among the arsenal of IFN-γ-inducible effectors needed for pathogen control.     

Spatial associations of insects and mites in stored wheat

The spatial association pattern of insect and mite populations in a steel bin containing stored wheat, Triticum durum Desf., in central Greece, was studied using the Spatial Analysis by Distance IndicEs (SADIE). The monitoring was carried out for 7 mo by using grain trier samples and probe traps. The most abundant insect species were Cryptolestes ferrugineus (Stephens) (Coleoptera: Laemophloeidae) and Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae). For mites, the most abundant species were the phytophagous Lepidoglyphus destructor (Schrank) (Acari: Glycyphagidae) and the predator Blattisocius tarsalis (Berlese) (Mesostigmata: Ascidae). Both for P. interpunctella and C. ferrugineus, trap catches were associated with numbers of individuals in the trier samples, but the overall association index calculated among trap and sample counts was significant only in the 33% of trap-sample pairs of values. Generally, P. interpunctella had the main patch areas in the central part of the bin, with few exceptions, during the entire monitoring period. Similar trends also were noted in the case of C. ferrugineus, which was clearly aggregated in the center of the grain mass. Spatial association maps indicated a stable positive association in the central part of the bin, but in most of the other sampling zones the association was negative. However, distribution of L. destructor, based on trier samples, indicated increased presence in peripheral zones of the grain sampling area. Moreover, B. tarsalis presented the most dispersed distribution among all four species. For each species, the association between two consecutive samplings was significant in the majority of cases, indicating a stable spatial pattern. Finally, B. tarsalis was spatially associated to a higher degree with the insects found rather than with L. desctructor. Moreover, there was no association of insect and mite presence with grain temperature and moisture content. The results of the current study suggest that the coexistence of insects and mites in bulked grain follows a complex pattern, with significant interactions, especially in the case of mite predators, which are spatially associated with insect species.     

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.     

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.     

The effects of the presence of stored product pests on the microfauna of a flour community

AIMS: To determine the effect that the presence of some beetles have on the species of bacteria found in their flour. METHODS AND RESULTS: Bacteria were isolated from flour that either did not contain beetles, contained Tribolium beetles in different environments, or contained either Stegobium paniceum or Lasioderma serricorne. These bacteria were tentatively identified by both the gas chromatography-fatty acid methyl esters (GC-FAME) method and partial sequencing of the 16S rRNA gene. All samples contained Bacillus species including the controls, but the non-Tribolium beetles and a Tribolium beetle line known to have low benzoquinones also contained Enterococcus and Enterobacter species. Additionally an unidentified bacteria isolate in the Enterobacteriaceae was also found in the L. serricorne sample. Our results also suggest incongruent identifications when using the GC-FAME method vs sequencing. CONCLUSIONS: Certain species of bacteria can be introduced by the presence of insect pests, but the diversity of species is far less in stocks of Tribolium beetles. SIGNIFICANCE AND IMPACT OF THE STUDY: Stored product pests can alter the bacterial community. Isolated species from this study show a strong genetic relationship to each other, suggesting an isolated evolving system. A unique bacteria was also isolated. GC and sequencing methods of identification are compared.     

The effects of dusts containing etrimfos,methacrifos or pirimiphos-methyl on mites in the surface layers of stored barley

Dusts containing etrimfos, methacrifos and pirimiphos-methyl controlledGlycyphagus destructor within 3 weeks when applied to the surface layers of a large bulk of barley stored at 1.5–8.0°C. Only etrimfos controlledAcarus siro.Laboratory tests on wheat at 17.5°C and 3°C suggested that low temperatures had retarded the action of the acaricides in the field. Etrimfos was also the most effective compound in the laboratory.     

Imaging techniques for the detection of stored product pests

Stored grains are subject to deterioration and losses through various factors, but mainly insects and fungi. Various techniques are employed to detect stored product pests; however, there is an urgent need for an industrial-scale on-line detection technique. Near-infrared hyperspectroscopic imaging and soft X-rays have shown the potential for real-time application. These techniques are particularly effective for detecting internal infestations of stored grains. The digital images of the scanned objects are analyzed for various spectral and image features using statistical techniques such as complex multivariate tools. Classification accuracies as high as 80–100 % have been achieved for various pest and grain combinations. Dual-energy X-rays have been shown to detect the concealed eggs of stored product insect pests. The main threats to stored cereals come from Aspergillus spp., Penicillium spp., and Fusarium spp., which may produce mycotoxins. These imaging techniques have shown good results in the detection of fungal infections of stored grain.     

The effect of monensin on chitin synthesis in Candida albicans blastospores

Monensin, a monovalent cation ionophore, was used to investigate some steps of the wall synthesis and morphogenesis in Candida albicans blastospores. In the presence of the drug, the pathogenic yeast developed enormous wall and septum thickenings that reacted intensely and specifically with wheat germ agglutinin and chitinase coupled to colloidal gold and fluorescein isothiocyanate. Therefore, the aberrant zones are interpreted as sites of chitin accumulation. The increased production of this homopolymer, also demonstrated by the chemical analysis of cell wall preparations, implies that monensin interferes in some way with the regulatory factors that normally control, in space and time, chitin synthetase activity.