Species spectrum of flea beetles (Phyllotreta spp., Coleoptera, Chrysomelidae) attracted to allyl isothiocyanate-baited traps

In field tests in Hungary, Slovenia and Bulgaria, in allyl isothiocyanate-baited traps significantly more beetles of Phyllotreta cruciferae, Ph. vittula, Ph. undulata, Ph. nigripes, Ph. nodicornis, Ph. balcanica, Ph. atra, Ph. procera, Ph. ochripes, Ph. diademata and Psylliodes chrysocephalus (Coleoptera, Chrysomelidae, Halticinae) were captured than in unbaited control traps. With the exception of Ph. cruciferae, this is the first report on significant field attraction by allyl isothiocyanate for these species. The species spectrum captured included six important agricultural pests. At all sites a great portion of the catch (ranging from ca 30 to 98%) was Ph. cruciferae, irrespective of the plant culture. The second most abundant species present at most sites was Ph. vittula. The present results are very promising from the point of view of applicability of allyl isothiocyanate in Europe as a bait in cabbage flea beetle traps for detection and monitoring.     

Effect of trichome density on soybean pod feeding by adult bean leaf beetles (Coleoptera: Chrysomelidae).

The role of soybean, Glycine max (L.) Merrill, pod trichomes on feeding by adult bean leaf beetles. Cerotoma trifurcata (Forster), was evaluated under laboratory and field conditions during 1997 and 1998. Three Clark isolines and 'Corsoy 79' were used to compare the feeding preference of the beetle on pods with different trichome densities. The three Clark isolines, including densely pubescent, sparsely pubescent, and glabrous, were isogenic except for trichome density. The trichome densities on the pods of Clark densely pubescent, Clark sparsely pubescent, and Corsoy 79 were significantly different. In no-choice tests, under both laboratory and field conditions, the feeding on pods of Clark densely pubescent was significantly lower than that on the other isolines. In the choice test of Corsoy 79 conducted in the laboratory and field, when the trichomes on one of the two pods were shaven off, the feeding on the shaven pods was significantly higher than that of the intact ones. In the choice test among Clark isolines under laboratory condition, the result was significant, with the lowest feeding on the densely pubescent pods. This study demonstrates that densely pubescent soybean has the potential to resist bean leaf beetle feeding on pods.     

Impact of planting dates and insecticide strategies for managing crucifer flea beetles (Coleoptera: Chrysomelidae) in spring-planted canola

Integration of cultural practices, such as planting date with insecticide-based strategies, was investigated to determine best management strategy for flea beetles (Phyllotreta spp.) (Coleoptera: Chrysomelidae) in canola (Brassica napus L.). We studied the effect of two spring planting dates of B. napus and different insecticide-based management strategies on the feeding injury caused by fleabeetles in North Dakota during 2002-2003. Adult beetle peak emergence usually coincided with the emergence of the early planted canola, and this resulted in greater feeding injury in the early planted canola than later planted canola. Use of late-planted canola may have limited potential for cultural control of flea beetle, because late-planted canola is at risk for yield loss due to heat stress during flowering. Flea beetle injury ratings declined when 1) the high rate of insecticide seed treatment plus a foliar insecticide applied 21 d after planting was used, 2) the high rate of insecticide seed treatment only was used, or 3) two foliar insecticide sprays were applied. These insecticide strategies provided better protection than the low rates of insecticide seed treatments or a single foliar spray, especially in areas with moderate-to-high flea beetle populations. The foliar spray on top of the seed treatment controlled later-emerging flea beetles as the seed treatment residual was diminishing and the crop became vulnerable to feeding injury. The best insecticide strategy for management of flea beetle was the high rate of insecticide seed treatment plus a foliar insecticide applied at 21 d after planting, regardless of planting date.     

Similarities in pheromonal communication of flea beetles Phyllotreta cruciferae Goeze and Ph. vittula Redtenbacher (Coleoptera,Chrysomelidae)

Remarkable similarities have been found in the pheromonal communication of Phyllotreta vittula Redtenbacher and of Ph. cruciferae Goeze (European population) (Coleoptera, Chrysomelidae). In previously published European field tests with Ph. cruciferae, only the major male‐produced sesquiterpene identified from North American Ph. cruciferae [compound A , (6R,7S)‐2,2,6,10‐tetramethylbicyclo[5.4.0]undeca‐1(11),9‐diene] was behaviourally active; unexpectedly, the European species Ph. vittula also responded in these tests and in the same way. In the present study, both the European population of Ph. cruciferae and Ph. vittula were shown to produce the same blend of compounds found in North American Ph. cruciferae and in similar proportions. Compound A is concluded to be a pheromone component for Ph. vittula as well as for Ph. cruciferae. In previously published tests with host compounds, Ph. vittula preferred 3‐butenyl isothiocyanate to allyl isothiocyante whereas the reverse was true for Ph. cruciferae. It was also learned earlier that compound A enhanced the response of both species toward allyl isothiocyanate. The present study further explored interactions between compound A and the two isothiocyanates. Thus, the highest catches of Ph. vittula were recorded in traps with the combination of racemic compound A with 3‐butenyl isothiocyanate, while highest Ph. cruciferae catches (and of Ph. nigripes Fabr.) were observed in traps with the combination of compound A with allyl isothiocyanate. Therefore, with the optimal combination of pheromonal and host‐derived stimuli, more specific communication channels may exist for the different Phyllotreta spp. Both Ph. cruciferae and Ph. vittula rank among the most important pest flea beetles in Europe.     

Comparative analysis of microbial diversity in Longitarsus flea beetles (Coleoptera: Chrysomelidae)

Herbivorous beetles comprise a significant fraction of eukaryotic biodiversity and their plant-feeding adaptations make them notorious agricultural pests. Despite more than a century of research on their ecology and evolution, we know little about the diversity and function of their symbiotic microbial communities. Recent culture-independent molecular studies have shown that insects possess diverse gut microbial communities that appear critical for their survival. In this study, we combined culture-independent methods and high-throughput sequencing strategies to perform a comparative analysis of Longitarsus flea-beetles microbial community diversity (MCD). This genus of beetle herbivores contains host plant specialists and generalists that feed on a diverse array of toxic plants. Using a deep-sequencing approach, we characterized the MCD of eleven Longitarsus species across the genus, several of which represented independent shifts to the same host plant families. Database comparisons found that Longitarsus-associated microbes came from two habitat types: insect guts and the soil rhizosphere. Statistical clustering of the Longitarsus microbial communities found little correlation with the beetle phylogeny, and uncovered discrepancies between bacterial communities extracted directly from beetles and those from frass. A Principal Coordinates Analysis also found some correspondence between beetle MCD and host plant family. Collectively, our data suggest that environmental factors play a dominant role in shaping Longitarsus MCD and that the root-feeding beetle larvae of these insects are inoculated by soil rhizosphere microbes. Future studies will investigate MCD of select Longitarsus species across their geographic ranges and explore the connection between the soil rhizosphere and the beetle MCD.     

Control of flea beetles Podagrica spp. (Coleoptera: Chrysomelidae) infestation on okra (Abelmoschus esculentus (L.) Moench) using Piper guineense seed extracts

Crops in the Family Malvaceae are attacked by various insect pests especially Podagria species (Coleoptera: Chrysomelidae) at different stages of their development. The emergence of biodegradable pesticides (botanicals) as safe option has reduced the problems that result from the use of synthetic insecticides, thus creating a renewed interest in their development and use in integrated pest management of crops. Therefore, field experiments were conducted to investigate the control capability of water extracts of Piper guineense seeds and Cypermethrin on flea beetles (Podagrica spp.) infesting okra (Abelmoschus esculentus (L.) Moench). The experiments were conducted in two locations in the rain forest zone of Nigeria. The first experiment was conducted at the Teaching and Research Farm of The Federal University of Technology Akure, Ondo State (2011 Early cropping season), while the second experiment was carried out at the Teaching and Research Farm of Rufus Giwa Polytechnic, Owo, Ondo State (2011 Late cropping season). A synthetic insecticide (Cypermethrin) was included in the treatments as a standard check alongside the untreated (control). The experimental design was laid out in a randomised complete block design with five treatments replicated three times. The effectiveness of the treatments was determined based on reduction in the population of the adult insects. The results showed that water extract of P. guineense seeds and the synthetic insecticide significantly (p?<?0.05) reduced the population of the flea beetles as compared with the control. The synthetic insecticide-treated plots produced the highest standard check, but this was not significantly different from the dried yield recorded in the plots sprayed with aqueous extracts of P. guineense seeds. The results of field trials in both cropping seasons showed that all the treatments significantly suppressed the infestation by the flea beetles throughout the study period. In view of the ability of water extract of P. guineense seeds to control the infestation of Podagrica spp. its use by farmers is therefore recommended.     

Comparisons of ecorational and chemical insecticides against crucifer flea beetle (Coleoptera: Chrysomelidae) on canola

Studies were done comparing the insecticides SpinTor (spinosad), BotaniGard (Beauveria bassiana), Neemix (azadirachtin), and Surround (kaolin, a clay) with conventional chemical insecticides Capture (bifenthrin) and Helix XTra (thiamethoxam), all applied at seven rates in a 7-d assay to assess their impact on adult crucifer flea beetle, Phyllotreta cruciferae (Goeze) (Coleoptera: Chrysomelidae). Lethal time (LT) required for 25, 50, and 75% mortality (LT25, LT50, and LT75) and relative potencies for the insecticide concentration groupings (0, 1X-1.5X, and 2X- 4X) were estimated for each treatment by using survival functions. P. cruciferae mortality increased in response to increasing concentrations, especially for Helix XTra, Capture and SpinTor. After 2 d of exposure in 2002, mortality ranged from 54 to 78% for Helix XTra, from 60 to 94% for Capture, and from 66 to 92% for SpinTor across concentrations. In 2003, flea beetle mortality ranged from 37 to 60%, from 29 to 63%, and from 23 to 52% on exposure to Helix XTra, Capture, and SpinTor, respectively, for 2 d. The LT50 and relative potencies of the insecticides were in the order of Helix XTra, Capture, and SpinTor > BotaniGard, Neemix, and Surround. In 2002, LT50 values were 1 and 2 d for Capture and SpinTor, 2 d for BotaniGard, and 3 d for Neemix and Surround. In 2003, LT50 values occurred between 2 and 4 d after exposure to Helix XTra, Capture, and SpinTor, with LT50 values of 5-7 d on exposure to BotaniGard, Neemix, and Surround. SpinTor seems to be a suitable ecorational insecticide in canola, Brassica napus L., for P. cruciferae management.     

Alternative management tactics for control of Phyllotreta cruciferae and Phyllotreta striolata (Coleoptera: Chrysomelidae) on Brassica rapa in Massachusetts

The flea beetles Phyllotreta cruciferae (Goeze) and Phyllotreta striolata (F.) (Coleoptera: Chrysomelidae: Alticinae) are significant pests of crops in the Brassicaceae family. From 2001 to 2003, the efficacy of both new and commonly used treatments for the control of flea beetles in brassicas, Brassica rapa L., were evaluated in three small plot, randomized complete block design trials. Row cover and carbaryl (applied as a weekly foliar spray) were found to be the most consistent at reducing damage in comparison with untreated controls in all trials. Two new products that may provide adequate flea beetle control are spinosad (in either conventional or organic formulations) and thiamethoxam. The plant-derived compounds azidiractin and pyrethrin did not protect treated plants from flea beetle feeding. Treatment of plants with kaolin, or removal of the beetles with a vacuum, also did not reduce the level of crop damage. The level of damage at harvest was found to be correlated with population size of flea beetles in each plot, as measured by captures on yellow sticky traps and direct visual counts. Removal of the outer two leaves of individual B. rapa plants reduced the total number of holes per plant by 40%, while only removing 15% of the leaf area.     

Isolation of polymorphic microsatellite loci from the flea beetle Phyllotreta nemorum L. (Coleoptera: Chrysomelidae)

Ten microsatellite markers for the flea beetle Phyllotreta nemorum were developed using di‐ and trinucleotide repeat‐enriched libraries. Each of these primer pairs were characterized on 96 individuals. Expected heterozygosities ranged between 0.11 and 0.84 and the number of alleles ranged between two and 14 per locus. These microsatellite markers are the first published for any Phyllotreta species.     

Yield reduction in Brassica napus, B. rapa, B. juncea, and Sinapis alba caused by flea beetle (Phyllotreta cruciferae (Goeze) (Coleoptera: Chrysomelidae)) infestation in northern Idaho

Phyllotreta cruciferae is an important insect pest of spring-planted Brassica crops, especially during the seedling stage. To determine the effect of early season P. cruciferae infestation on seed yield, 10 genotypes from each of two canola species (Brassica napus L. and Brassica rapa L.) and two mustard species (Brassica juncea L. and Sinapis alba L.) were grown in 2 yr under three different P. cruciferae treatments: (1) no insecticide control; (2) foliar applications of endosulfan; and (3) carbofuran with seed at planting plus foliar application of carbaryl. Averaged over 10 genotypes, B. rapa showed most visible P. cruciferae injury and showed greatest yield reduction without insecticide application. Mustard species (S. alba and B. juncea) showed least visible injury and higher yield without insecticide compared with canola species (B. napus and B. rapa). Indeed, average seed yield of S. alba without insecticide was higher than either B. napus or B. rapa with most effective P. cruciferae control. Significant variation occurred within each species. A number of lines from B. napus, B. juncea, anid S. alba showed less feeding injury and yield reduction as a result of P. cruciferae infestation compared with other lines from the same species examined, thus having potential genetic background for developing resistant cultivars.     

Field evaluation of entomopathogenic nematodes for biological control of striped flea beetle, Phyllotreta striolata (Coleoptera: Chrysomelidae)

The striped flea beetle, Phyllotreta striolata (F.) (Coleoptera: Chrysomelidae) is a key pest of crucifer vegetables in Southern China. The use of entomopathogenic nematodes (EPNs) within an integrated pest management approach may offer an effective and environmentally safe strategy to suppress outbreaks of this pest. In the present study, the efficacy of Steinernema carpocapsae All and Heterorhabditis indica LN2 for the control of P. striolata in the field was evaluated, as well as the combined application of EPNs and azadirachtin against the pest. Both nematode species were capable of reducing populations of the soil-dwelling stages of P. striolata, thus leading to a reduction of the adult populations and the associated shot-hole damage on the leaves. Nematode treatments also increased cabbage yields as compared to the control and azadirachtin treatments alone. Azadirachtin alone was not effective to prevent damage by P. striolata, but it could enhance the control effect of S. carpocapsae shortly after application. Osmotically treated infective juveniles (IJs) of S. carpocapsae All performed as well as untreated IJs.     

Study on salt tolerance with YHem1 transgenic canola (Brassica napus)

5‐Aminolevulinic acid (5‐ALA) has been suggested for improving plant salt tolerance via exogenous application. In this study, we used a transgenic canola (Brassica napus), which contained a constituted gene YHem1 and biosynthesized more 5‐ALA, to study salt stress responses. In a long‐term pot experiment, the transgenic plants produced higher yield under 200 mmol L^?1 NaCl treatment than the wild type (WT). In a short‐term experiment, the YHem1 transformation accelerated endogenous 5‐ALA metabolism, leading to more chlorophyll accumulation, higher diurnal photosynthetic rates and upregulated expression of the gene encoding Rubisco small subunit. Furthermore, the activities of antioxidant enzymes, including superoxide dismutase, guaiacol peroxidase, catalase and ascorbate peroxidase, were significantly higher in the transgenic plants than the WT, while the levels of O₂·^? and malondialdehyde were lower than the latter. Additionally, the Na⁺ content was higher in the transgenic leaves than that in the WT under salinity, but K⁺ and Cl^? were significantly lower. The levels of N, P, Cu, and S in the transgenic plants were also significantly lower than those in the WT, but the Fe content was significantly improved. As the leaf Fe content was decreased by salinity, it was suggested that the stronger salt tolerance of the transgenic plants was related to the higher Fe acquisition. Lastly, YHem1 transformation improved the leaf proline content, but salinity decreased rather than increased it. The content of free amino acids and soluble sugars was similarly decreased as salinity increased, but it was higher in the transgenic plants than that in the WT.     

Chromosomes of some Puerto Rican flea beetles (Coleoptera: Chrysomelidae: Alticinae): multiple cytogenetic evolutionary tendencies in the neotropics

Meiotic chromosomes of 10 West Indian flea beetles with restricted distribution, including eight Puerto Rican endemics, were studied. Two species of the cosmopolitan Longitarsus resemble Old World congenerics in having meioformulae 13 + Xy and 14 + Xy, both with one pair of enlarged autosomes. One unidentified species of Aphthona seems to have achiasmatic meiosis. Among the Puerto Rican endemics, repeated fusions have produced low-numbered karyotypes in Homoschema latitarsum (2 + neoXY, now the lowest meioformula known for the Chrysomelidae) and Heikertingerella krugi (4 + neoXY). Three species of Aedmon have 18 + Xy_p as a result of a series of centric fissions from the Polyphagan ancestral condition of nine pairs. Phyllotrupes sp. (a new genus record for Puerto Rico, near P. acutangula ) and Pseudodisonycha portoricensis have 17 + Xy and 16 + Xy, respectively, plus a swarm of supernumerary chromosomes.     

Effect of a phloxine B-cucurbitacin bait on diabroticite beetles (Coleoptera: Chrysomelidae)

Cucurbitacin E glycoside, extracted from a bitter mutant of Hawkesbury watermelon [Citrulls lanatus (Thunb.) Matsum. & Nakai (Syn. Citrullus vulgaris Schrad)] is the active ingredient of a feeding stimulant for the corn rootworm complex. It is the primary component of a water-soluble bait that can be combined with toxins for adult diabroticite control. Studies were conducted using phloxine B (D&C Red 28), a xanthene dye, as the toxin. This dye was efficacious against Diabrotica undecimpunctata howardi Barber, spotted cucumber beetle, and Acalymma vittatum (F.), striped cucumber beetle, in cucumber plots and could be recovered from cucumber leaves for 8 d after treatment. The average amount of dye recovered per dead spotted cucumber beetle at 8 d after treatment was 0.173 microg. Concentrated and sugar-free fermented forms of the watermelon extract were developed and compared with the fresh juice in field applications on cucumber plants. There was no significant difference in mortality of beetles from phloxine B-bait prepared with fresh, fermented, or concentrated extract, although in laboratory studies, fermented juice had higher feeding stimulant activity.     

基于Solexa高通量测序的黄曲条跳甲转录组学研究

黄曲条跳甲Phyllotreta striolata (Fabricius) 是十字花科蔬菜的重要害虫。为深入了解其遗传信息, 本研究应用新一代高通量测序技术Illumina’s Solexa平台对黄曲条跳甲成虫的转录组进行测序, 并结合SOAPdenovo拼接聚类等分析软件, 获取大量的EST和挖掘功能基因。本文最终获得了4 924条序列重叠群（contig）, 其中包含2 209种与黑腹果蝇Drosophila melanogaster蛋白基因具直系同源的独立基因（unigene）和610种黄曲条跳甲物种特有的unigene。结合Gene Ontology （GO）数据库进行分析, 发现大部分的unigene具结合能力（binding capability）和催化活性（catalytic activity）; 上百种unigene可聚类于生物学过程分类中的配子发生、 生殖腺发育和交配行为等重要功能。另外, 结合KEGG Pathway数据库分析发现, 共有363种unigene参与或涉及了40种代谢路径, 其中生物钟调控路径和植物次生代谢物路径等相关基因的发现, 有助于深入研究黄曲条跳甲行为发生的内在机理。Solexa高通量测序技术作为昆虫功能基因组研究的重要手段, 为发掘黄曲条跳甲功能基因发挥了重要作用, 也为在分子水平上研发黄曲条跳甲的防治新策略提供了更翔实的基因信息。     

Relative susceptibility of two sweetpotato varieties to storage root damage by sweetpotato flea beetle (Coleoptera: Chrysomelidae) and wireworm (Coleoptera: Elateridae)

The feeding of soil dwelling insects on storage roots is one of the most serious management issues faced by sweetpotato, Ipomoea batatas (L.) Lam. (Convolvulaceae), growers in the southern United States. Field studies were conducted to evaluate the relative susceptibility of two commonly grown sweetpotato varieties to sweetpotato flea beetle, Chaetocnema confinis Crotch (Coleoptera: Chrysomelidae), and wireworms (Coleoptera: Elateridae, various species). The incidence and severity of sweetpotato flea beetle damage was significantly lower in the variety Covington than Beauregard in two small plot replicated studies. Surveys conducted in commercial sweetpotato fields also showed significantly less sweetpotato flea beetle damage in fields planted to Covington compared with those planted to Beauregard. There was no clear evidence of varietal effect on the incidence of wireworm damage in the study. Results indicate that the severity of wireworm damage as measured by the size of feeding scars may be less in Covington than Beauregard.     

Resistance of temperate Chinese elms (Ulmus spp.) to feeding by the adult elm leaf beetle (Coleoptera: Chrysomelidae)

Newly acquired Ulmus species from the temperate regions of China growing at The Morton Arboretum, Lisle, IL, were evaluated in laboratory bioassays for feeding preference and suitability for larvae and adults of the elm leaf beetle, Pyrrhalta luteola (Müller). Larval and adult no-choice and adult multiple-choice feeding studies revealed that U changii, U. lanceaefolia, U. prunifolia, U. pseudopropinqua, and U. taihangshanensis were the least suitable for feeding and reproduction by the elm leaf beetle. Ulmus wallichiana and the highly preferred U pumila were more suitable for feeding and reproduction. Suitability had no significant effect on male and female longevity. The least suitable species of U. changii, U. lanceaefolia, U. prunifolia, U. pseudopropinqua, and U. taihangshanensis show promise for future elm breeding programs.     

Susceptibility of willow clones (Salix spp.) to herbivory by Phyllodecta vulgatissima (L.) and Galerucella lineola (Fab.) (Coleoptera, Chrysomelidae)

Levels of damage by mixed natural infestations of the leaf-feeding chrysomelid beetles, Phyllodecta vulgatissima (L.) (the blue willow beetle) and Galerucella lineola (Fab.) (the brown willow beetle), were determined in replicated field plots of 24 Salix clones at Long Ashton (Bristol, UK) during 1993–94. Over the same period, the host plant preferences of both chrysomelids were investigated in a standard multiple-choice laboratory procedure, where beetles were enclosed in Petri dishes with leaf discs cut from young pot-grown trees propagated from shoot cuttings taken from 20 of the 24 willow clones represented in the field study. The laboratory experiments indicated that P. vulgatissima and G. lineola had similar host plant preferences in the range of willows examined (r >0.85). In both field and laboratory, the least preferred Salix clones and hybrids were those of 5. eriocephala, followed by S. purpurea, S. burjatica, S. dasyclados and S. triandra. Clones of S. eriocephala and S. purpurea were frequently rejected altogether in laboratory tests. Most preferred were clones of S. viminalis and several hybrids of S. viminalis, S. aurita, S. caprea and S. cinerea. These results substantiate the reports that P. vulgatissima and G. lineola are deterred from feeding on willows which have relatively high concentrations of phenolic (salicylate) glucosides in the leaves. The least preferred willows, particularly S. eriocephala, S. purpurea and S. burjatica, could be of great potential value in plant breeding for resistance to these willow beetle pests.     

Host plant discrimination within Cruciferae: Feeding responses of four leaf beetles (Coleoptera: Chrysomelidae) to glucosinolates, cucurbitacins and cardenolides

Feeding responses of four Chrysomelidae to six less acceptable plants and to compounds from them were investigated by means of leaf disc tests. Significant differences were found between responses of different species, and plants containing potent feeding inhibitors were always rejected. Cucurbitacins are potent feeding inhibitors to Phyllotreta nemorum, and this species does not eat Iberis species containing these compounds. Cardenolides are potent feeding inhibitors to P. undulata, P. tetrastigma and Phaedon cochleariae, and these three species do not eat the cardenolide containing Cheiranthus and Erysimum.Six different glucosinolates all proved to be stimulatory when applied to pea leaf discs. Although the glucosinolates differed somewhat in their ability to stimulate feeding, no correlation is found between content of glucosinolates and acceptability of the investigated plants. Application of sinigrin to Iberis and Cheiranthus did not improve their acceptability. The presence of glucosinolates is necessary for feeding to occur, but it is less important which glucosinolates are present.Cardenolides and cucurbitacins are suggested to be a second generation of protective compounds in Cruciferae, glucosinolates being the first.

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Zusammenfassung Der Einfluss einiger sekundärer Pflanzenstoffe aus Cruciferen auf die Futteraufnahme von vier Chrysomeliden, die auf dieser Pflanzenfamilie vorkommen, wurde mittels Blattscheiben-Tests untersucht. Cucurbitacine sind starke Frasshemmstoffe für Phyllotreta nemorum, weniger starke Hemmstoffe für P. undulata und schwache Hemmstoffe für P. tetrastigma und Phaedon cochleariae. Iberis-Arten, die Cucurbitacine enthalten, werden von P. nemorum und P. undulata abgelehnt, von den beiden anderen Arten aber akzeptiert. Cardenolid-Glykoside vom Strophanthidin-Typ sind starke Frasshemmstoffe für P. undulata, P. tetrastigma und Phaedon cochleariae. Diese Arten lehnen Cheiranthus-und Erysimum-Arten, die solche Stoffe enthalten, ab. Die Futteraufnahme von P. nemorum wird von diesen Stoffen nicht beeinflusst; P. nemorum akzeptiert Cheiranthus- und Erysimum-Arten.Futteraufnahme fand bei Abwesenheit von Senfölglukosiden nicht statt. Sechs verschiedene Senfölglukoside waren alle imstande, das Aufnehmen von Erbsen-Blattscheiben zu stimulieren. Gewisse Unterschiede in der stimulierenden Wirkung der einzelnen Glukoside wurden gefunden. Das Vorkommen bestimmter Glukoside und die Akzeptabilität der Pflanzen zeigten aber keine Korrelation. Anwesenheit oder Abwesenheit von Frasshemmstoffen beeinflusst die Akzeptabilität der Pflanzenarten mehr als die Anwesenheit bestimmter Senfölglukoside.Wenn Senfölglukoside als eine erste Generation von Abwehrstoffen in Cruciferen aufgefasst werden, können Cucurbitacine in Iberis und Cardenolid-Glykoside in Cheiranthus und Erysimum als eine zweite betrachtet werden.

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The Danish Natural Science Research Council supported the research.     

Host plant selection of the horse-radish flea beetle Phyllotreta armoraciae (Coleoptera: Chrysomelidae): Feeding responses to glucosinolates from several crucifers

Feeding responses of Phyllotreta armoraciae, a monophagous flea beetle feeding on horseradish, Armoracia rusticana, were evaluated by means of leaf disc tests. Semiquantitative determinations of the glucosinolate contents found in leaves of twelve species of Cruciferae, including horseradish, were performed. The responses of P. armoraciae to the twelve plant species were evaluated, as were the responses to pure glucosinolates and to glucosinolate mixtures occurring in the plants.The glucosinolate content of horseradish consisted of more than 99% allylglucosinolate together with traces of 2-butyl-and benzylglucosinolate. Nearly the same pattern occurred in Brassica nigra, Alliaria petiolata, Iberis umbellata, and Thlaspi arvense, but only the first-mentioned species was acceptable in laboratory bioassays. Nasturtium microphyllum, Sinapis alba, and Sisymbrium officinale did not contain allylglucosinolate as a major component, but nevertheless, these species were acceptable to P. armoraciae in the laboratory. The glucosinolate mixtures isolated from Nasturtium microphyllum, Sisymbrium officinale, Alyssum saxatile, and Cardamine amara were even more stimulating than glucosinolates from horseradish. The two latter species together with Iberis amara and Raphanus sativus were not eaten by P. armoraciae.All acceptable plants contained highly stimulatory mixtures of glucosinolates but several glucosinolates contributed to these mixtures and P. armoraciae did not prefer the glucosinolates of horseradish above those of most other investigated crucifers. Therefore, horseradish cannot be recognized by the beetles solely by its content of glucosinolates. Other feeding stimulants and(or) absence of feeding inhibitors seem to play a major role.

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Zusammenfassung Das Wirtswahlverhalten des monophagen Erdflohs, Phyllotreta armoraciae, der auf Meerrettich, Armoracia rusticana, lebt, wurde mittels Blattscheiben-Tests untersucht.Glukosinolate stimulieren die Futteraufnahme von vielen Insekten, die auf Cruciferen leben. Wahrscheinlich erkennt ein monophages Insekt seine Wirtspflanze durch Reaktionen auf Stoffe die dieser Pflanze eigen sind. Eine Untersuchung der Affinität zwischen P. armoraciae und den Glukosinolaten des Meerrettichs wurde deshalb unternommen.Glukosinolate aus zwölf Cruciferae wurden isoliert, und eine semiquantitative Bestimmung durchgeführt. Gleichzeitig wurden die isolierten Glukosinolat-Mischungen auf Erbsenblattscheiben überführt und die frassstimulierende Wirkung gemessen.Der Glukosinolatinhalt des Meerrettichs besteht aus 99% Allylglukosinolat und Spurmengen von 2-butyl-und Benzylglukosinolat. Fast derselbe Gehalt wurde in Brassica nigra, Alliaria petiolata, Iberis umbellata und Thlaspi arvense gefunden, aber nur die ersterwähnte Art wurde in Labor-Tests akzeptiert. Obwohl Allylglukosinolat keine Hauptkomponente in Nasturtium microphyllum, Sinapis alba und Sisymbrium officinale ist, werden diese Arten doch von P. armoraciae im Labor akzeptiert. Vier anderen Cruciferen werden nicht akzeptiert.Die aus N. microphyllum, S. officinale, Alyssum saxatile und Cardamine amara isolierten Glukosinolat-Mischungen stimulieren die Futteraufnahme mehr als die Glukosinolat-Mischung aus Meerrettich. Nur die Glukosinolat-Mischung aus Iberis amara wirkt weniger stimulierend als die Mischung aus Meerrettich.Pflanzenarten, die von P. armoraciae akzeptiert werden, enthalten Glukosinolat-Mischungen mit hoher frassstimulierende Wirkung. Diese Wirkung ist nicht an einzelne Glukosinolate oder Glukosinolat-Mischungen geknüpft, und P. armoraciae erkennt den Meerrettich unter anderen Cruciferen nicht am Gehalt an Glukosinolaten.Einige Pflanzenarten werden nicht akzeptiert, obwohl sie frassstimulierende Glukosinolate enthalten. Vielleicht fehlen bei diesen Arten andere notwendige frassstimulierende Stoffe, oder (und) sie enthalten vielleicht frasshemmende Stoffe.