Cereal Leaf Beetle Research Articles

Distinct barcodes for the Cereal leaf beetles Oulema melanopus and Oulema duftschmidi (Coleoptera: Chrysomelidae), two syntopical sibling species

Oulema melanopus (Linnaeus, 1758) and Oulema duftschmidi (Redtenbacher, 1874) (Coleoptera: Chrysomelidae) are two native West Palaearctic species developing on various cultivated and wild grasses. Along with O. obscura they are considered to be secondary pests of cereal crops. However, local outbreaks have been recorded recently and their status as secondary pests may evolve, especially as the use of broad-spectrum insecticides is now greatly reduced. Oulema melanopus and O. duftschmidi are considered to be sibling species. They are morphologically very close and difficult to distinguish from each other, which makes it difficult to study them. We tested the reliability of the standard barcode fragment (COI) for distinguishing between these species. A total of 92 samples of the two species, covering the majority of their natural range, was sequenced for the barcode fragment and inter- and intraspecific genetic distances were estimated. Our results confirm those of Bezděk & Baselga (2015, Acta Entomol. Mus. Nat. Prag. 55: 273-304) in that this marker cannot differentiate between all the species of the Oulema melanopus complex, which in the Mediterranean basin contains several described and possibly some undescribed cryptic species. However, this marker may be useful in an agricultural context in areas where only O. melanopus and O. duftschmidi occur (such as in cereal crops in France) where it can be used to reliably and rapidly separate all stages of these two taxa and can therefore help in studying their ecology and dynamics.

Pantoea ananatis, A New Bacterial Pathogen Affecting Wheat Plants (Triticum L.) in Poland.

Wheat (Triticum aestivum) is one of the most economically important crops in the world. During the routine monitoring of wheat pest, the cereal leaf beetle (CLB, Oulema melanopus, Coleoptera, Chrysomelidae), in the Greater Poland region, it was observed that some leaves wounded by CLB also displayed brownish lesions with clear margins and yellow halo, disease symptoms resembling a bacterial infection. The aim of this study was therefore to investigate those symptoms to establish a causal agent of the disease. The identification based on the results of the Biolog’s Gen III system, 16S rRNA, and gyrB genes sequencing, revealed the presence of eight strains of Pantoea ananatis bacteria. Four strains were derived from wheat leaves (Ta024, Ta027, Ta030, Ta046), and four from the CLB’s oral secretion (OUC1, OUD2, OUF2, and OUG1). They shared the nucleotide identity ranging from 99 to 100% to P. ananatis strains deposited in the GenBank database. Additionally, the multi-locus sequence analysis (MLSA) of concatenated sequences of partial atpD, fusA, gyrB, rplB, and rpoB genes was performed. All P. ananatis strains isolated in Poland, grouped into one cluster supported with high bootstrap value. Pathogenicity tests performed on four varieties of wheat plants have identified P. ananatis strains as a causal agent of wheat disease. To our knowledge, this is the first report of P. ananatis affecting wheat plants.

The assessment of winter wheat agrocenoses adaptivity in the conditions of the submontane zone of the Central Caucasus

The article presents the results of 3 years study on the adaptation of the properties of various winter wheat varieties to the conditions of the submontane zone of the Central Caucasus. The indicator of the ontogenetic adaptability was the homeostaticity of the plants. We have studied thirty winter wheat varieties according to the parameters of ecological plasticity, productivity and resistance to the destructive complex of diseases and pests like Fusarium head blight, brown and yellow rust, Septoria blight, tan spot etc. The yield of the mixed variety crops was 4.5 t/ha; the increase was 9%. In the crops of the triple mixture of the strong Veda and Delta varieties (25%) with the valuable Batko variety (50%), which differed in resistance to various diseases, the average yield of 52 cwt/ha was obtained with the protein content of 12%, the gluten content of 28% and the flour strength of 320 a.u. The authors used the resistance of the precocious Kuma variety to the damage by the cereal leaf beetle as a protective screening crop along with the field perimeter. Such a screening crop of the stable variety prevents the colonization of the crops of the other less resistant varieties with pests. The genetic diversity of the variety creates the conditions for regulating and stabilizing the phytosanitary state of the crops and increasing their productivity. With this agrotechnical method, it becomes possible to regulate and stabilize the phytosanitary situation in the fields and to increase grain productivity and quality.

Analysis of the count of populations and harmfulness of phytophages of agrocenoses of grain cereals of the Central ForestSteppe of Ukraine

The count of harmful entomofauna, damage to plants by phytophages and the proportion of their colonization of soft wheat (winter and spring) and common barley (spring) in the Central Forest-Steppe of Ukraine in the spring-summer period of 2004–2019 were analyzed. Such specialized pests as: leafhoppers (Macrosteles laevis Ribaut, Psammotettix alienus L., Calligypona striatella Fall.), aphids (Schizaphis graminum (Rondani), Macrosiphum (Sitobion) avenae (F.), Brachycolus (Cuernavaca) noxius Mordv., Rhopalosiphum padi (L.)), grain bugs (Eurygaster integriceps Put., Eurygaster maura L., Eurygaster austriaca Schrank, Aelia acuminata L.), wheat trips (Haplothrips tritici Kurd.), common ground beetle (Zabrus tenebrioides Goeze), аnisoplia austriaca beetle (Anisoplia austriaca Herbst, Anisoplia segetum Herbst), grain flea beetles (Phyllotreta vittula Redt., Chaetocnema hortensis Geoffr., Chaetocnema aridula Gyll.), cereal leaf beetle (Oulema melanopus (L.), Oulema lichenis Voet.), cereal flies (Oscinella frit L., Oscinella pusila Meigen, Mayetiola destructor (Say), Phorbia securis Tiensuu etc.) were the most common in agrocenoses of grain crops in a harmful entomocomplex. Polyphagous insects, namely caterpillars of gnawing scoops (Scotia segetum Schiff., Scotia exclamationis L.), also caused significant damage in cereal crops. It was revealed that a complex of sucking pests is numerous on winter wheat, represented by wheat thrips (Haplothrips tritici Kurd.), Cereal aphids (Macrosiphum (Sitobion) avenae F., Schizaphis graminum Rond.), Grain sawflies (Cephus pygmaeus L., Trachelus tabidus F.), on spring wheat grain flea beetles (Phyllotreta vittula Redt., Chaetocnema aridula Gyll.) and wheat thrips, on spring barley – grain flea beetles and cereal aphids. Under favorable conditions for overwintering, warm, moderately humid weather in spring and dry weather in summer, active colonization and an increase in the number of phytophages led to their exceeding in 2.5–5.7 times of the economic threshold of harmfulness. Under these conditions, the number of grain bugs (Eurygaster integriceps Put., Е. austriacus Schrnk., Е. maura L., Aelia acuminata L., Dolycoris baccarum L.) in some years reached 8– 15 ind./m2 , ground beetles — up to 20 ind./m2, grain beetles — up to 17 ind./m2, cereal aphids — up to 50 ind./plant.

Genetic Architecture of Cereal Leaf Beetle Resistance in Wheat.

Wheat production can be severely damaged by endemic and invasive insect pests. Here, we investigated resistance to cereal leaf beetle in a panel of 876 winter wheat cultivars, and dissected the genetic architecture underlying this insect resistance by association mapping. We observed an effect of heading date on cereal leaf beetle infestation, with earlier heading cultivars being more heavily infested. Flag leaf glaucousness was also found to be correlated with resistance. In line with the strong effect of heading time, we identified Ppd-D1 as a major quantitative trait locus (QTL), explaining 35% of the genotypic variance of cereal leaf beetle resistance. The other identified putative QTL explained much less of the genotypic variance, suggesting a genetic architecture with many small-effect QTL, which was corroborated by a genomic prediction approach. Collectively, our results add to our understanding of the genetic control underlying insect resistances in small-grain cereals.

Linear woody landscape elements may help to mitigate leaf surface loss caused by the cereal leaf beetle

ContextWoody semi-natural habitats serve as permanent habitats and hibernation sites for natural enemies and, through spillover processes, they play an important role in the biological control of insect pests. However, this service is also dependent on the amount and configuration of the dominating woody habitat types: linear landscape elements (hedgerows, shelterbelts), and more evenly extended plantations. Relating natural enemy action to the landscape context can help to identify the effect of woody habitats on biological control effectiveness.ObjectivesIn the Central European agricultural landscapes such as in the Hungarian lowlands, where our study took place, woody linear elements are characterised by high, while woody areal elements, mostly plantations, by low biological and structural diversity. In this study, we aimed to determine which composition and configuration of woody linear and areal habitats in the landscape may enhance the effect of natural enemy action on plant damage caused by the cereal leaf beetle (CLB, Oulema melanopus).MethodsHerbivory suppression by natural enemies was assessed from the leaf damage difference between caged and open treatments. These exclusion experiments were carried out in 34 wheat fields on plants with controlled CLB infections. The results were related to landscape structure, quantified by different landscape metrics of both woody linear and areal habitats inside buffers between 150 and 500 m radii, surrounding the wheat fields.ResultsThe exclusion of natural enemies increased the leaf surface loss caused by CLBs in all fields. Shelterbelts and hedgerows in 150–200 m vicinity of the wheat fields had a strong suppressing effect on CLB damage, while the presence of plantations at 250 m and further rather impeded natural enemy action.ConclusionsOur results indicate that shelterbelts and hedgerows may provide a strong spillover of natural enemies, thus contribute to an enhanced biological control of CLBs.

Ecological structure of harmful entomocomplex of agrocenoses of cereal crops of the Central ForestSteppe of Ukraine

Species composition of harmful entomofauna in agrocoenosis of grain crops in Central Forest-steppe of Ukraine is specified. 54 species of insects-phytophages from 22 families and 8 orders are ascertained. In taxonomic structure of harmful entomocomplex representatives of such orders as Cоleoptera (18 species), Diptera (11), Hemiptera (8), Homoptera (8), Lepidoptera (5 species) dominated. The order of coleopterous (Coleoptera), which makes 33% in the structure of entomocomplex, was characterized with numerous species diversity among insects. The order of dipterous (Diptera) numbered 11 species from 5 families that made 20%. Representatives hemipterous (Hemiptera) and homopterous (Homoptera) orders were represented by the same number of species (8) that made 15% for each one in entomocomplex structure. Orders of hymenopterous (Hymenoptera), thysanopterous (Thysanoptera) and orthopterous (Orthoptera), which made jointly 8% in entomocomplex structure, were characterized with the least numerous specious diversity (1 family, 1–2 species). In wheat and barley agrocoenosis phytophils (hortobionts – 43 species from 18 families) dominated, portion of which made 79.6%. Geophils were represented with the less species diversity and numbered 11 species from 5 families among which geobionts (8 species from 3 families) dominated. The most numerous (dominant) species in 2004–2019 were such pests as corn-bug (Eurygaster integriceps Put.), turnip dart (Scotia segetum Schiff.), blue cereal leaf beetle (Oulema lichenis Voet.), cereal leaf beetle (Oulema melanopus L.), barley flea beetle (Phyllotreta vittula Redt.), click beetle (Agriotes sputator L.), fruit fly (Oscinella frit L.), striped leafhopper (Psammotettix striatus L.), green bug (Schizaphis graminum Rond.), corn sawfly (Cephus pygmaeus L.), wheat thrips (Haplothrips tritici Kurd.), which harmed greatly cereal crops.

Partial bivoltinism in a gregarious endoparasitoid: larval diapause as influenced by season and sharing a host

AbstractThe yearly timing of the life cycle of a parasitoid is a key element of its life‐history strategy. I examine here factors influencing the expression of partial bivoltinism in Tetrastichus julis Walker (Hymenoptera: Eulophidae), a specialist parasitoid introduced to North America to attack its univoltine host, the cereal leaf beetle, Oulema melanopus (L.) (Coleoptera: Chrysomelidae). The varying tendency was assessed of individuals of this gregarious larval parasitoid to either emerge as adults in the same summer they mature, or to enter diapause to emerge the following year. Parasitized hosts were obtained by rearing cereal leaf beetles collected as mature larvae from grain fields in northern Utah (western USA) throughout the growing seasons in 2013 and 2014. Cocoons spun by these beetles were held to determine patterns over the spring and summer in the tendency of the parasitoid to forgo larval diapause. A high percentage (nearly 90% in 2013) of parasitoid individuals were found to forgo diapause and emerge in the same summer from earliest maturing hosts. This percentage rapidly declined to 20% or less of individuals forgoing diapause and emerging from cocoons as the summer advanced. The percentage of parasitoid individuals forgoing diapause increased significantly at a given time of season (early or late) as the number of conspecifics with which an individual shared a host larva increased. These results may reflect a trade‐off for individual parasitoids in which greater success in finding – and ovipositing in – host larvae the following spring vs. in summer, is countered by reduced survivorship in diapausing over the winter vs. emerging in the same summer in which the parasitoid matures. Expression of partial bivoltinism of T. julis, as affected strongly by both season and within‐host density, results in high rates of parasitism of cereal leaf beetles both early and late in the season.

Experimental Assessment of the Economic Injury Level of the Cereal Leaf Beetle (Coleoptera: Chrysomelidae) in Winter Wheat.

The cereal leaf beetle, Oulema melanopus L., is an economically important pest species, reducing crop yields in many cereal growing parts of the world. Available studies on yield depression in winter wheat in relation to the density of O. melanopus revealed inconsistent results, creating uncertainty about economic thresholds for pest control. We present results from a series of controlled field trials over a 4-yr period (2014-2017) in Switzerland to examine the impact of artificial defoliation (0, 20, 40, and 60% of flag leaf area removed in 1-m2 field plots) on yield and yield components in winter wheat. The applied defoliation treatments correspond to field infestations levels of approximately 2-6 larvae per stem. Analysis of the combined data from 11 location-years revealed a significant linear decrease in yield per ear with increasing defoliation intensity. Yield per ear declined at a rate of 1.14% (SE = 0.28) per 10 percentage-point increase in defoliation. Similar results were found in a parallel series of field trials in which a 40% defoliation treatment was applied to eight common wheat cultivars. Interestingly, however, three cultivars showed complete tolerance in yield to defoliation. Data from two trials with natural defoliation by larvae revealed equally low levels of yield loss by feeding of O. melanopus. Based on the experimentally derived yield loss function, we calculated economic injury levels for a range of crop values. These will serve as benchmarks in the development of IPM decision-support tools for managing cereal leaf beetles in winter wheat.

Contrasting effects of host crops and crop diversity on the abundance and parasitism of a specialist herbivore in agricultural landscapes

Landscape complexity affects herbivores in agroecosystems, but consequences on pest control services are variable. Carryover effects of landscape composition in previous years on herbivore control may be important, but have been seldom assessed. Understanding landscape complexity effects at different temporal and spatial scales is important to improve sustainable pest control services. We examined the effect of agricultural landscape complexity (e.g., the percentage of semi-natural habitats) on cereal leaf beetle (CLB), Oulema melanopus L., and its parasitism by Tetrastichus julis (Walker). From 2014 to 2015, we assessed CLB abundance and parasitism in 54 fields along a gradient of landscape complexity (2–70% of semi-natural habitats) in southern Alberta. We used generalized linear models to test the effects of percentage of crops and semi-natural habitats, and landscape and crop diversity on CLB abundance and parasitism at 0.5, 1, 1.5 and 2 km spatial scales. CLB abundance decreased with higher crop diversity at the 0.5 km scale and increased with CLB host crops in the current and previous years at multiple scales, supporting the resource concentration hypothesis. CLB parasitism increased with CLB abundance and in landscapes with increased canola and alfalfa during a year of low CLB abundance. CLB abundance had contrasting associations with semi-natural habitats: positive with woodlands and negative with pastures. Our study suggests that crop diversity reduces the abundance of this specialist pest in agricultural landscapes likely by a dual effect of reducing host crop area and increasing habitats with resources for parasitoids.

Host Specificity of the Parasitic Wasp Anaphes flavipes (Hymenoptera: Mymaridae) and a New Defence in Its Hosts (Coleoptera: Chrysomelidae: Oulema spp.)

The parasitic wasp Anaphes flavipes (Förster, 1841) (Hymenoptera: Mymaridae) is an important egg parasitoid of cereal leaf beetles. Some species of cereal leaf beetle co-occur in the same localities, but the host specificity of the wasp to these crop pests has not yet been examined in detail. A lack of knowledge of host specificity can have a negative effect on the use of this wasps in biological control programs addressed to specific pest species or genus. In this study, laboratory experiments were conducted to assess the host specificity of A. flavipes for three species of cereal leaf beetles (Oulema duftschmidi Redtenbacher, 1874, Oulema gallaeciana Heyden, 1879 and Oulema melanopus Linnaeus, 1758) in central Europe. For the first time, a new host defence against egg parasitoids occurring in O. gallaeciana from localities in the Czech Republic, a strong dark sticky layer on the egg surface, was found and described. The host specificity of A. flavipes was studied in the locality with the presence of this defence on O. gallaeciana eggs (the dark sticky layer) (Czech Republic) and in a control locality (Germany), where no such host defence was observed. Contrary to the idea that a host defence mechanism can change the host specificity of parasitoids, the wasps from these two localities did not display any differences in that. Respectively, even though it has been observed that eggs with sticky dark layer can prevent parasitization, the overall rate of parasitization of the three species of cereal beetles has not been affected. However, in our view, new host defence can influence the effects of biological control, as eggs of all Oulema spp. in the locality are protected against parasitization from the wasps stuck on the sticky layer of the host eggs of O. gallaeciana.

Novel Host-Bacterial Symbioses Revealed: Characterization of Wolbachia in Arthropods of Western North America

Arthropod-bacterial symbioses are prevalent and play significant roles in ecosystems and the economy, and in some cases, habitat invasion. Wolbachia bacteria form symbiotic associations with a wide range of arthropod hosts and can affect both host reproduction and resistance to viral infections. The extent to which Wolbachia infects different arthropod species is fundamental not only to host biology, but also to the health of humans, ecosystems, and agriculture. Much of what we know about the effects of Wolbachia comes from a few key taxa, such as the model organism Drosophila melanogaster and the mosquito vector of human disease, Aedes aegypti. The majority of arthropods, even at higher taxonomic levels, have not been tested for infection, with a lack of surveys conducted in western North America. We screened and characterized Wolbachia diversity in arthropods in 2 types of collections in western North America: broad surveys and targeted collections of species known to be infected with Wolbachia. Our goals were to (1) find new Wolbachia strains and hosts, (2) characterize Wolbachia in commonly studied taxa to see whether there are different infection frequencies or strain types in this location, and (3) compare new Wolbachia strains in western North America to previously characterized strains. PCR screening of broadly sampled arthropods with Wolbachia-specific 16S rDNA (W16S) identified 5 novel host species. Three of these are invasive: a ground beetle, Nebria brevicollis (Coleoptera: Carabidae); a cereal crop agricultural pest, Oulema melanopus (Coleoptera: Chrysomelidae); and a residential nuisance pest, Raglius alboacuminatus (Hemiptera: Rhyparochromidae). The crab spider Philodromus dispar (Araneae: Philodromidae) is nonnative, though not considered invasive, and the hyaline grass bug Liorhyssus hyalinus (Hemiptera: Rhopalidae) is of undetermined origin. To characterize 9 novel Wolbachia strains in our collections, we analyzed the 5-gene MultiLocus Sequence Type (MLST) and the Wolbachia surface protein gene (wsp). We identified 10 novel alleles among 5 MLST genes and 10 novel alleles of the highly variable regions (HVR) of wsp. This is the first report of Wolbachia hosts and strain identification from the Pacific Northwest and Rocky Mountain regions. These studies contribute to our understanding of the natural history of arthropod hosts, the biogeography of Wolbachia, and host-symbiont evolution. Moreover, strain identification is the first step in implementing Wolbachia-based biocontrol for conservation and pest mitigation, including control of the invasive N. brevicollis, O. melanopus, and R. alboacuminatus reported herein.

Consumption of cereal leaf beetle, Oulema melanopus, by generalist predators in wheat fields detected by molecular analysis

AbstractThe cereal leaf beetle (CLB), Oulema melanopus L. (Coleoptera: Chrysomelidae), is a major pest of cereal crops that has recently been reported in western Canada. We developed a set of primers to detect CLB DNA in the gut of six common predator taxa in wheat fields: lady beetles (20 positives of 143 individuals), nabid bugs (73 positives of 206 individuals), and wolf spiders (2 positives of 25 individuals). Nabis americoferus Carayon (Hemiptera: Nabidae) and Coccinella septempunctata L. (Coleoptera: Coccinellidae) were the most abundant predators in cereal fields, with 0.35 and 0.05 proportion of samples positive for CLB DNA, respectively. The prey DNA half‐lives were used to adjust the estimates for N. americoferus to 0.22, due to its longer DNA detectability relative to C. septempunctata. Overall, Hippodamia parenthesis (Say) (Coleoptera: Coccinellidae) had the highest proportion of positives at 0.43. There was a positive association between CLB abundance and proportion of N. americoferus and C. septempunctata positives for CLB DNA. This study highlights the contribution of generalist predators to CLB mortality and their important role in integrated management for CLB. Furthermore, we provide a molecular tool that can be used to identify predators of CLB and predation frequency in agricultural fields.

Laboratory Bioassay of Selected Entomopathogenic Nematodes as Mortality Factors of Oulema melanopus (Coleoptera: Chrysomelidae)

The biological activity of entomopathogenic nematodes (EPNs) against the larvae and adults of the economically important Oulema melanopus (L.) (Coleoptera: Chysomelidae) was assessed under laboratory conditions. The EPNs assessed were five native isolates of the species Steinernema feltiae (Filipjev) and Heterorhabditis megidis (Poinar, Jackson, and Klein). Steinernema feltiae (isolate ZAG15) demonstrated the highest biological activity, causing 100% of mortality of larvae and beetles. The lowest activity occurred with H. megidis (isolate Wipsowo), with mortality that did not exceed 58%. At a concentration of 100 infective juveniles/adult, greatest mortality of beetles was observed at 25°C as opposed to lower temperatures for all EPN isolates except the Wipsowo isolate, which showed no statistical significance of mortality among the temperatures tested. At 15°C, adult beetle mortality was concentration-dependent with the S. feltiae isolates ZWO4 and ZAG15. However, neither concentration nor temperature had statistically significant effects on larval mortality.

Effects of mechanical injury and insect feeding on volatiles emitted by wheat plants

We report on changes in the volatiles emitted by wheat plants of the cultivar ‘Tonacja’ after the plants were scraped, pierced or damaged by adults of Oulema melanopus (Linnaeus). The blend of volatiles was dominated by typical green leaf volatiles and in addition contained linalool and B-caryophyllene, but the latter two were released in large amounts only after more than one day of insect feeding. Overall, the plants that had been damaged by the insect released more odors than the plants that were subjected to mechanical damage. Moreover, control plants released significantly lower amounts of volatiles. Scraping of leaves induced higher volatile emission than puncturing the leaves. A Y-tube bioassay was used to evaluate upwind orientation ofadult cereal leafbeetles. Greater number of female 0. melanopus was attracted to (Z)-3-hexenal and (Z)-3 -hexenyl acetate at low concentrations. Higher concentration of these compounds and linalool significantly repelled both females and males.

Inter- and Intrafield Distribution of Cereal Leaf Beetle Species (Coleoptera: Chrysomelidae) in Belgian Winter Wheat.

Cereal leaf beetles (CLBs), a group of chrysomelid beetles of the genus Oulema (Coleoptera: Chrysomelidae), are well-known pest insects of small-grain cereals in many countries of the Northern hemisphere. Due to the small differences in morphology of species within this genus, classification up to species level remains a challenging task. Since an accurate view of species composition is important for developing targeted control strategies, the goal of this study was to unravel the Oulema species composition in Flanders' wheat fields. During three subsequent years at a series of different fields, Oulema species were collected and classified up to species level (2016: 28 fields, 2017: 30 fields, and 2018: 23 fields). This study reveals that the population consists of four different species: Oulema melanopus, Oulema duftschmidi, and Oulema obscura were most frequently encountered, while Oulema rufocyanea was only marginally present. Furthermore, the population was highly dynamic, as the population share of each species varied between different growing seasons and between the various sampling events within each season. The distance from the field edge had a minor influence on the species composition, but the abundance of beetles increased with the distance to the field edge. A discriminant analysis revealed that based on the measurements of various body parts, an accurate classification up to species level is possible. In conclusion, we observed that the population densities fluctuated within and between years, resulting in variable incidence of CLB in winter wheat fields in the Flanders region.

Laboratory and field tests of predation on the cereal leaf beetle, Oulema melanopus (Coleoptera: Chrysomelidae)

ABSTRACTThe cereal leaf beetle (CLB), Oulema melanopus (L.) (Coleoptera: Chrysomelidae), is an invasive pest in North America recently reported in the Canadian Prairies. We performed a series of laboratory assays to identify potential predators and a field study to quantify predation of CLB eggs. In no-choice Petri dish assays, ground beetles (Carabidae), rove beetles (Staphylinidae), and several common lady beetle species (Coccinellidae) were the most consistent predators of eggs and larvae. Nabis spp. (Hemiptera: Nabidae) and wolf spiders (Araneae: Lycosidae) consumed many larvae, but did not consume eggs. Hippodamia spp., Coccinella septempunctata (L.) (Coleoptera: Coccinellidae), and Pterostichus melanarius (Illiger) (Coleoptera: Carabidae) also fed on CLB eggs on potted plants when an alternative food source was available, Sitobion avenae (Fabricius) (Hemiptera: Aphididae). In our field study, we found an average of 24.5% of sentinel eggs disappeared over a 24 h period, likely due to predation. Our results suggest that generalist predators can play an important role in the biological control of CLB, and warrant further study.

The Importance of Integrated Pest Control on Wheat Crops Production, during 2015-2016, at Agricultural Research-Development Station Turda

In the wheat crops of central Transylvania a rich complex of phytophagous insects species is reported. Species of thrips, aphids, leafhoppers, flies, cereal leaf beetle and cereal bugs, affects the level of production and quality indicators of wheat grains. In the period of 2015-2016, various integrated pest control models have been applied, watching their effect on the production and quality indicators of wheat, based on applied insecticide treatments, in the experimental lots at ARDS Turda. The results on the quantified production parameters showed oscillations over previous multiannual values, due to the special climatic conditions of 2015 and 2016, to the density of entomophagous and phytophagous insect populations, influenced by the applied treatment system. It is noted that in the years 2015-2016, characterized as exceptional years, with unfavorable thermal and pluviometric conditions, with much higher values than the multiannual average, the gluten and protein content, zeleny index have lower values than in the previous years, at ARDS Turda. The specific annual climate characteristics have a major influence on the production and quality of wheat. Also, pest control strategies have a major impact on the production parameters and qualitative indicators of wheat.

Dispersal in Host⁻Parasitoid Interactions: Crop Colonization by Pests and Specialist Enemies.

Interactions of insect pests and their natural enemies increasingly are being considered from a metapopulation perspective, with focus on movements of individuals among habitat patches (e.g., individual crop fields). Biological control may be undercut in short-lived crops as natural enemies lag behind the pests in colonizing newly created habitat. This hypothesis was tested by assessing parasitism of cereal leaf beetle (Oulema melanopus) and alfalfa weevil (Hypera postica) larvae at varying distances along transects into newly planted fields of small grains and alfalfa in northern Utah. The rate of parasitism of cereal leaf beetles and alfalfa weevils by their host-specific parasitoids (Tetrastichus julis (Eulophidae) and Bathyplectes curculionis (Ichneumonidae), respectively) was determined for earliest maturing first generation host larvae. Rates of parasitism did not vary significantly with increasing distance into a newly planted field (up to 250–700 m in individual experiments) from the nearest source field from which pest and parasitoid adults may have immigrated. These results indicate strong, rapid dispersal of the parasitoids in pursuing their prey into new habitat. Thus, across the fragmented agricultural landscape of northern Utah, neither the cereal leaf beetle nor the alfalfa weevil initially gained substantial spatial refuge from parasitism by more strongly dispersing than their natural enemies into newly created habitat. Additional studies, including those of colonization of newly planted crops by generalist pests and natural enemies, are called for in assessing these results with a broader perspective.

Dynamics of leaf beetles density (Coleoptera, Chrysomelidae) in grain crops agrocoenoses of the Samara Region

The author studied winter and spring wheat (Trticum) development dynamics in the Volga Region left-bank forest-steppe zone during 19742010 in natural conditions and gardens on the Samara Region cereal crops fields, as well as generation cycles of 6 local species of leaf beetles, with 1-year development, 5 of which do a lot of harm to wheat (Oulema melanopus L., Phyllotreta vittula Redt., Chaetocnema aridula Gyll., Chaetocnema hortensis Geoffr., Hispella atra L.) and 1 (Cassida rubiginosa Mll.) is the consumer of a weed plant Cirsium arvense (L.) Scop.). The author also studied leaf beetles density dynamics and their localization on grain crops of different age. The author studied cereal crops agrocoenoses microclimate under different weather conditions, different plants vegetation intensity at different times of the day. The author also studied major stages of beetles harmful species generation and the timing of their implementation. The paper contains an analysis of the extent and timing of different harmfulness of leaf beetles; the economic value of their separate types. The author surveyed the conditions preferred by the pests of wheat as well as the factors depressing their larval stage and considered the cases of beetles and larvae massive aggregations formation and beetles migration into more comfortable areas. The author comes to the conclusion of the extraordinary plasticity and adaptability of the leaf to the microclimatic conditions of the habitat.