Václav Stejskal

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.

Accumulation of pest-arthropods in grain residues found in an empty store

The aim of this work was to explore the species composition and abundance of mites and insects in grain residues in an empty grain store. Sampling was done the first and the fifth week after unloading of the wheat grain from the store.In the study, altogether 26 species of arthropods (Acarina, Psocoptera, Hymenoptera, Coleoptera) were found in the grain residues. Primary and secondary pests created 84 % and predators and parasitoids represented altogether 16 % of the whole arthropod’s community. Primary pests Acarus siro and Sitophilus granarius were dominant. This study documented the accumulation and increase of pests in residues of old grain after unloading the grain-store. The number of individuals increased 3–450 times within 1 month depending on the species. The practical importance of the ”empty-store-management“, which usually escapes the attention of farmers is highlighted.ZusammenfassungIn der vorliegenden Arbeit wurden Artenzusammensetzung und Abundanz von Milben und Insekten in Getreideresten in einem entleerten Speicher untersucht. Die Probenahmen erfolgten in der ersten und fünften Woche nach der Entleerung des Weizenlagers. Es wurden insgesamt 26 Arten Arthropoden (Acarina, Psocoptera, Hymenoptera, Coleoptera) in den Getreideresten gefunden. Primäre und sekundäre Schädlinge hatten einen Anteil von 84 % und Prädatoren und Parasitoide von 16 % am Gesamtvorkommen der Arthropoden. Die primären Schädlinge Acarus siro und Sitophilus granarius überwogen. Die Ergebnisse dieser Untersuchung dokumentieren die Anhäufung und Zunahme der Schädlinge in alten Getreidekörnern nach Entleerung des Speichers. Die Zahl der Individuen erhöhte sich 3- bis 450-fach innerhalb eines Monats je nach Art. Die Bedeutung für die Praxis des Manage-ments von leeren Getreidespeichern, der die Farmer normalerweise keine Beachtung schenken, wird hervorgehoben.

Validation of the 16S rDNA and COI DNA Barcoding Technique for Rapid Molecular Identification of Stored Product Psocids (Insecta: Psocodea: Liposcelididae)

ABSTRACT Psocids are serious storage pests, and their control is hampered by the fact that different species respond differently to insecticides used for the control of stored-product insect pests. Additionally, psocids of genus Liposcelis that are commonly associated with stored-products are difficult to identify using morphological characteristics. The goal of this study was to validate molecular identification of stored-product psocids of genus Liposcelis based on 16S rDNA and cytochrome oxidase I (COI) DNA barcoding. Unidentified liposcelids (Liposcelis_DK) imported from Denmark to China were compared with 14 population samples of seven common species (L. bostrychophila, L. brunnea, L. corrodens, L. decolor, L. entomophila, L. mendax, and L. paeta). The explored species (DK) liposcelids shared >98% sequence similarity for both the 16S rDNA and COI genes with the reference L. corrodens samples (98.32 and 98.94% for 16S rDNA and COI, respectively). A neighbor-joining tree revealed that the explored DK sample and the reference L. corrodens samples belong to the same clade. These molecular results were verified by morphological identification of DK specimens, facilitated by SEM microphotography. The DNA barcoding method and the neighbor-joining phylogenetic analyses indicated that both the 16S rDNA and COI genes were suitable for Liposcelis species identification. DNA barcoding has great potential for use in fast and accurate liposcelid identification.

Comparison of Detection Methods for Acarus siro (Acari: Acaridida: Acarididae) Contamination in Grain

Abstract 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 μg 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.

Efficacy of selected pesticides against synanthropic mites under laboratory assay

BACKGROUND The efficacies of organophosphate pesticides, single-compound versus multicompound pyrethroid formulations and relatively novel unclassified insecticides/acaricides were compared to find the lowest dosage and highest efficacy for the control of Dermatophagoides farina (Hughes), D. pteronyssinus (Trouessart) and Tyrophagus putrescentiae (Schrank). Formulated active ingredients (AIs) were diluted in water and applied onto filter paper in experimental chambers with ten unsexed adult mites in six replicates. Mite mortality was checked after 24 h. The security index (SI) was calculated for all of the AIs by dividing the recommended rate by the LD(90) determined for each species. RESULTS The tested organophosphates had high LD(90) and low SI values. The single-compound pyrethroids were ineffective (deltamethrin and beta-cyfluthrin) or had high LD(90) and low SI values (cyphenothrin, permethrin, pyrethrum and bifenthrin). The multicompound miticides had low LD(90) and high SI values which increased from deltamethrin/S-bioallethrin to permethrin/S-bioallethrin/piperonyl butoxide to permethrin/pyriproxyfen/benzyl benzoate. Abamectin, pyridaben, propargite and flufenoxuron were highly active against Dermatophagoides spp. Neem (Acarosan duo) was highly active against all mite species tested. CONCLUSION The available formulations of multicompound pyrethroids (permethrin/S-bioallethrin/piperonyl butoxide, permethrin/pyriproxyfen/benzyl benzoate), benzyl benzoate, neem and some field acaricides are effective in suppression of synanthropic mites in laboratory assays. Their LD(90) are lower than those of traditionally used organophosphates or single-compound pyrethroid formulations.

In vitro and in vivo inhibition of α-amylases of stored-product mite Acarus siro

Abstract.The stored-product mites are the most abundant and frequent group of pests living on the stored food products in Europe. They endanger public health since they produce allergens and transmit mycotoxin-producing fungi. Novel acaricidal compounds with inhibitory effects on the digestive enzymes of arthropods are a safe alternative to the traditional neurotoxic pesticides used for control of the stored-product pests. In this work, we explored the properties of acarbose, the low molecular weight inhibitor of α-amylases (AI), as a novel acaricide candidate for protection of the stored products from infestation by Acarus siro (Acari: Acaridae). In vitro analysis revealed that AI blocked efficiently the enzymatic activity of digestive amylases of A. siro, and decreased the physiological capacity of mite’s gut in utilizing a starch component of grain flour. In vivo experiments showed that AI suppressed the population growth of A. siro. The mites were kept for three weeks on experimental diet enriched by AI in concentration range of 0.005 to 0.25%. Population growth of A. siro was negatively correlated with the content of AI in the treated diet with a half-population dose of 0.125%. The suppressive effect of AIs on stored-product mites is discussed in the context of their potential application in GMO crops

Comparative egg morphology of silvanid and laemophloeid beetles (Coleoptera) occurring in stored products

Eggs of eight pest species of Silvanidae and Laemophloeidae commonly occurring in stored products (grain and flour etc.) in Europe are described. Comparisons include overall appearance, size, surface sculpturing and changes in external appearance during development of the embryo. Morphological details are illustrated with scanning electron micrographs. A key for distinguishing eggs of these pests at generic level is provided. The study did not reveal structural characters of value for distinguishing eggs at the species level and thus the development of specific immunological or molecular identification methods is suggested.

The influence of food and shelter on the efficacy of a commercial sticky trap in Tribolium castaneum (Coleoptera: Tenebrionidae)

Abstract The effect of the presence of food and shelter on the dispersion behaviour of Tribolium castaneum was measured by means of the Trappit- Tribolium trap. The following experimental designs were used: I. trap only, II. paper shelter + trap, III. food + trap, IV. shelter + food + trap. The behaviour of beetles was recorded for 30 d. For the “Trappit” efficacy evaluation the number of beetles entrapped on glue proved to be a better parameter than the total number of insects arrested in the trap, due to large variations of the latter caused by migration between entry channels of traps and the surrounding environment. On day 30 the average trap catches decreased according to experimental design in the following order: I (trap only), II (paper shelter), III (food + trap), and IV (shelter + food + trap). Significantly lower catches were recorded in designs containing food or shelter + food. The paper shelter used alone was found to be a weak competitor to traps. Two types of trapping rate of T. castaneum were observed which were triggered by the presence (linear response) or absence (exponential response) of food in the arena.

Distribution of faeces of the German cockroach, Blattella germanica, in a new refuge

The patterns of faeces deposition in glass arenas with three groups of Blattella germanica L. during colonization of new refuges were recorded. The individual positions of more than 17,500 faeces were recorded. The average daily rate of faeces excretion per adult was 9.6 in males, 9.1 in non‐gravid females and 2.7 in gravid females. Significant differences of faeces accumulation at various sites of the arena were found. In all three groups, mean density of faeces decreased in the following order: shelter, edges of arena, area around shelter, remainder of open area. The faeces were not accumulated more significantly at food and water sources than within the remainder of the open area. Low concentrations of faeces around edges were recorded with gravid females. The ratio of numbers of faeces in the shelter and those on the remainder of the arena was nearly identical in all tested groups. The rate of faeces deposition fluctuated during colonization of a new refuge. The role of faeces containing aggregation pheromone and ammonia in the ecology and behaviour of B. germanica is discussed.

Emerging risk of infestation and contamination of dried fruits by mites in the Czech Republic.

The introduction of live insects into human food is rare in developed countries. However, we report, for the first time, an emerging risk that exists from dried fruit in Central Europe. Recently, massive and frequent infestation of dried fruit imported from the Mediterranean region by the mite, Carpoglpyhus lactis L. (Acarina: Carpoglyphidae), has been found. In 180 samples taken from supermarkets, 13% were contaminated; the contamination levels ranged from 0 to 660 mites per g of dried fruit. The contamination was found in dried apricots, figs, plums and raisins. To estimate the risks and food preferences of C. lactis, its growth rate was examined under laboratory conditions. Starting with a hypothetical population of 10 mites per g of dried fruit, the risk level of 1000 mites per g of dried fruit is reached at 42 days for dried figs, 49 days for dried pineapple and 63 days for dried apricots, dates and plums at 25°C and 85% relative humidity. We found that mites are able to enter every dried fruit packing material tested, including polypropylene and aluminum foils. This indicates that mites can move from package to package in supermarkets. Mites are known as allergen producers and vectors of mycotoxin-producing fungi. These findings indicate that an increased risk of C. lactis contamination exists in dried fruit.