<Emphasis Type="Italic">n</Emphasis>-Alkane assimilation and <Emphasis Type="Italic">tert</Emphasis>-butyl alcohol (TBA) oxidation capacity in <Emphasis Type="Italic">Mycobacterium austroafricanum</Emphasis> strains

Mycobacterium austroafricanum IFP 2012, which grows on methyl tert-butyl ether (MTBE) and on tert-butyl alcohol (TBA), the main intermediate of MTBE degradation, also grows on a broad range of n-alkanes (C₂ to C₁₆). A single alkB gene copy, encoding a non-heme alkane monooxygenase, was partially amplified from the genome of this bacterium. Its expression was induced after growth on n-propane, n-hexane, n-hexadecane and on TBA but not after growth on LB. The capacity of other fast-growing mycobacteria to grow on n-alkanes (C₁ to C₁₆) and to degrade TBA after growth on n-alkanes was compared to that of M. austroafricanum IFP 2012. We studied M. austroafricanum IFP 2012 and IFP 2015 able to grow on MTBE, M. austroafricanum IFP 2173 able to grow on isooctane, Mycobacterium sp. IFP 2009 able to grow on ethyl tert-butyl ether (ETBE), M. vaccae JOB5 (M. austroaafricanum ATCC 29678) able to degrade MTBE and TBA and M. smegmatis mc2 155 with no known degradation capacity towards fuel oxygenates. The M. austroafricanum strains grew on a broad range of n-alkanes and three were able to degrade TBA after growth on propane, hexane and hexadecane. An alkB gene was partially amplified from the genome of all mycobacteria and a sequence comparison demonstrated a close relationship among the M. austroafricanum strains. This is the first report suggesting the involvement of an alkane hydroxylase in TBA oxidation, a key step during MTBE metabolism.     

Identity of a powdery mildew fungus occurring on Paeonia and its relationship with Erysiphe hypophylla on oak

A powdery mildew fungus found on Paeonia lutea at the Botanical Garden of Geneva (Switzerland) was identified as Erysiphe hypophylla based on morphological observations. The occurrence of E. hypophylla on Paeonia seemed curious, because host plants of this species have been restricted to a few Quercus species of the family Fagaceae. In this study, we determined the rDNA sequences of the powdery mildew specimens on Paeonia and E. hypophylla on Quercus to confirm the identity of the Paeonia fungus. The three sequences from the specimens on P. lutea were identical to one another in both ITS and 28S rDNA regions and also to the sequences of E. hypophylla on Q. robur, which supports the identification that the fungus on P. lutea is E. hypophylla. However, these sequences were also identical to the sequences of E. alphitoides on Quercus spp. and Oidium mangiferae on mango. This result suggests a possibility that E. hypophylla is conspecific to E. alphitoides. Further study is required to clarify whether E. hypophylla is a synonym of E. alphitoides or a distinct species.     

<Emphasis Type="Italic">Puccinia calystegiae-soldanellae</Emphasis>, a new rust species on <Emphasis Type="Italic">Calystegia soldanella</Emphasis> from Japan

A rust species on Calystegia soldanella in Japan has been treated as Puccinia convolvuli to date. However, morphological characteristics of specimens on C. soldanella collected from Japan are significantly different from those of specimens on other Calystegia and Convolvulus species from different areas of the world. It is proved by inoculation experiment that the rust on C. soldanella is specific to C. soldanella. Based on these results, Puccinia rust on C. soldanella from Japan is described as a new species, Puccinia calystegiae-soldanellae.     

Addition and re-examination of Japanese species belonging to the genus <Emphasis Type="Italic">Cercospora</Emphasis> and allied genera. X: newly recorded species from Japan (5)

Cercospora yakushimensis is proposed as a new combination, Pseudocercospora yakushimensis comb. nov., and the morphology of the species is characterized from herbarium specimens, including the type. Six additional species belonging to the genus Cercospora and its allied genera are newly added to the Japanese mycoflora, namely, Cercospora dioscoreae-pyrifoliae on Dioscorea tokoro, Pseudocercospora catalpigena on Catalpa ovata, Pseudocercospora coriariae on Coriaria japonica, Pseudocercospora lythri on two species of Lythrum, Pseudocercospora pteroceltidis on Celtis boninensis, and Passalora puncta on Foeniculum vulgare.     

Plant-based host preference and larval competition of the tachinid parasitoid Epicampocera succincta

We investigated the causes of among-plant variation in the parasitism rate of Pieris melete larvae (Lepidoptera: Pieridae) by the parasitoid fly Epicampocera succincta (Diptera: Tachinidae). The rate of parasitism by E. succincta was much higher on the bitter cress Cardamine appendiculata than on any other cruciferous plants. Adult female flies were found to be more attracted to C. appendiculata than to other cruciferous plants for searching for hosts. The parasitoid appeared to be unable to distinguish P. melete from an alternative host, Pieris rapae larvae, that coexisted with P. melete on most crucifer plants. Similarly, E. succincta failed to avoid P. rapae parasitized by the braconid wasp Cotesia glomerata. C. glomerata is a superior competitor to E. succincta if occupying the same host, killing the host before the E. succincta larva can grow and depriving the larva of the chance to survive. E. succincta attacked P. rapae larvae on most cruciferous plants, many of which were already occupied by C. glomerata; only on Cardamine appendiculata was E. succincta free from interspecific competition, because only P. melete was found on this particular plant. However, the strong preference for the hosts on C. appendiculata incurred heavy intraspecific competition among larvae on this plant, killing as great a proportion of larvae as interspecific competition did on the other plants. The balance between the strength of intraspecific competition on the preferred plant and of interspecific competition on the other plants appeared to maintain plant preference by E. succincta. Received: November 13, 2000 / Accepted: April 27, 2001     

Predators mediate host plant resistance to a phytophagous pest in cabbage with glossy leaf wax

This study examined the role of generalist predators in producing higher mortality ofPlutella xylostella L. (Plutellidae) larvae on glossy vs. normal-wax cabbage,Brassica oleracea var.capitata L. To test this, survival and feeding ofP. xylostella were measured on individually caged glossy and normal-wax plants with and without each of three generalist predators,Chrysoperla carnea (Stephens) (Chrysopidae),Orius insidiosus (Say) (Anthocoridae), andHippodamia convergens Guerin-Meneville (Coccinellidae). In the greenhouse, predators always significantly reduced survival ofP. xylostella larvae on glossy plants, but never on normal-wax plants. In the field, predators significantly reducedP. xylostella survival on glossy plants, but onlyC. carnea was effective on normal-wax plants. In similar experiments with excised leaves,O. insidiosus andC. carnea were more effective predators on the glossy leaves, whileH. convergens was equally effective on both kinds of leaves. Patterns for feeding were similar, but significance levels differed from those forP. xylostella survival. The greater effectiveness of predators on glossy plants is apparently due to the reported improved mobility of these animals on glossy leaf surfaces. The data also suggest that reduced mining byP. xylostella exposes the larvae to more predation on glossy plants and contributes some to the resistance. Regardless of the mechanism, resistance toP. xylostella on glossyB. oleracea appears to depend on the action of generalist predators for its full expression. This dependence on predation must be considered in the development and deployment of glossy insect-resistantB. oleracea.     

Development and Reproduction of Ladybeetles (Coleoptera: Coccinellidae) on the Citrus Aphids Aphis spiraecola Patch and Toxoptera citricida (Kirkaldy) (Homoptera: Aphididae)

Seven species of Coccinellidae inhabiting citrus groves in Florida were evaluated for ability to develop and reproduce on the citrus aphids Toxoptera citricida (Kirkaldy) and Aphis spiraecola Patch. Choice tests performed with adults and larvae indicated that both aphid species were generally acceptable prey. Coccinella septempunctata L., Coleomegilla maculata fuscilabris (Mulsant), Coelophora inaequalis F., and Olla v-nigrum Mulsant were unable to complete development on either aphid. Hippodamia convergens Guerin larvae completed development on A. spiraecola with 68% survival; none survived on T. citricida. Only Cycloneda sanguinea (L.) and Harmonia axyridis Pallas completed development on both A. spiraecola (60 and 70% survival, respectively) and T. citricida (100 and 95% survival, respectively). Larval developmental time was shorter on T. citricida than on A. spiraecola, and resulting adults were heavier, differences being more pronounced in H. axyridis. Females of C. septempunctata, C. inaequalis, and O. v-nigrum produced viable eggs on T. citricida. O. v-nigrum did not produce eggs on A. spiraecola. Females of C. m. fuscilabris and H. axyridis produced no eggs on A. spiraecola and mostly infertile eggs on T. citricida. Female H. convergens laid twice as many eggs feeding on T. citricida as on A. spiraecola and egg viability was similar. C. sanguinea females laid similar numbers of eggs on both aphids, but eggs produced on A. spiraecola had higher fertility. Pollen added to the T. citricida diet temporarily improved the fertility of H. axyridis females, but not that of C. sanguinea females. C. sanguinea was judged the best candidate for augmentative biocontrol of T. citricida, the primary vector of citrus tristeza virus.     

Effects of diet on development and reproduction of the predatory pentatomids Picromerus bidens and Podisus maculiventris

The effects of five diets (larvae of Galleria mellonella L., larvae of Spodoptera littoralis (Boisduval), eggs of Ephestia kuehniella Zeller, cysts of Artemia franciscana Kellogg and an artificial diet based on bovine meat) on development, survival and reproduction of two predatory stinkbugs, Picromerus bidens L. and Podisus maculiventris (Say), were studied in the laboratory. Both species successfully completed immature development on the foods offered, except for P. bidens on cysts of A. franciscana. Significant effects of diet on developmental duration were found in both species. Total developmental time from second instar to adult ranged from 25.0 to 41.5 days and from 18.7 to 46.0 days in P. bidens and P. maculiventris, respectively. Nymphal survival of P. maculiventris was superior to that of P. bidens on all diets tested. Nymphal survival of P. maculiventris was greater than 92% on all diets except on A. franciscana cysts, yielding only 50% survival to adulthood. Survival of P. bidens fed on eggs of E. kuehniella was higher than that of conspecifics fed on caterpillar prey or artificial diet (89% on flour moth eggs vs. 68 and 80% on G. mellonella and S. littoralis and only 50% on meat diet). Fresh weight of newly emerged females of both pentatomids was affected by the diet offered to the predators during their nymphal stage. Females of P. maculiventris produced viable eggs on all diets except on cysts of A. franciscana and had mean fecundities of 691, 436, 608 and 344 eggs per female on S. littoralis, G. mellonella, E. kuehniella eggs and the meat diet, respectively. Females of P. bidens laid eggs only on live prey with mean fecundities of 94 and 38 eggs per female on S. littoralis and G. mellonella, respectively. The results indicate a lower nutritional plasticity of P. bidens as compared with P. maculiventris. An erratum to this article can be found at     

Multiple factors promoting narrow host range in the sea hare,Aplysia californica

Summary Juvenile sea hares, Aplysia californica, utilize only the red algae Plocamium cartilagineum and Laurencia pacifica as host plants at Santa Catalina Island, CA. I tested three hypotheses which might account for this pattern of host choice: 1) A. californica specialize on the algae on which they grow best, 2) A. california specialize on algae from which they acquire secondary compounds that protect them from predators, and 3) A. californica specialize on certain algae in order to lower their encounter rates with predators. The results suggested that host range in the Aplysia californica system is affected by more than one factor. The first hypothesis was supported. A. californica of three size classes grew well on Plocamium, but could not grow at all on most other species of algae. Larger A. californica were able to grow on species of algae that smaller ones could not. The second hypothesis was also supported. Small A. californica grown on Plocamium were rich in terpenes. Small A. californica grown on Ulva sp. were terpene-free. Rock wrasses, Halichoeres semicinctus, were more likely to eat Ulva-fed A. californica than Plocamium-fed A. californica. Other fish and lobster, Panulirus interruptus, did not discriminate between the two groups. Kelp bass, Paralabrax clathratus, which were force-fed Ulva-fed A. californica regurgitated them less often, and after digesting them more completely, than did Paralabrax force-fed Plocamium-fed A. californica. The third hypothesis was rejected. A. californica located on Plocamium were not more cryptic to the opisthobranch Aglaja inermis (navanax), or to the pomacentrid fish, Hypsypops rubicundus, than were A. californica located on other algae. In addition, navanax, a specialist predator of opisthobranchs, was significantly more abundant on Plocamium than on other algae.     

The host range and biology of the mesquite psyllid Heteropsylla texana

Prosopis spp. areintroduced rangeland weeds in Australia. In asearch for biological control agents, thepsyllid Heteropsylla texana, which causessevere distortion to growing leaf and floralshoots, was imported from Texas, USA forhost range testing in quarantine facilities.No-choice tests were conducted on 60 plantspecies including P. pallida, P. velutinaand P. juliflora. In these trials, adultssurvived on 45 non-target plants but ovipositedonly on the Prosopis spp., Dichrostachys spicata and Acaciabidwillii. Nymphs developed to ovipositingadults on all Prosopis spp. and both D. spicata and A. bidwillii. Developmentof small numbers of adults on D. spicataand A. bidwillii occurred for only onegeneration. Damage was noticed only on Prosopis spp. In multiple-choice trials usingthree plant species, oviposition and subsequentdevelopment of eggs and nymphs to adults tookplace on P. pallida and D. spicatabut not on A. bidwillii. The low numbersdeveloping, the longer development times toadults when reared on D. spicata and A.bidwillii, and the failure of these plantsto sustain populations beyond one generationindicate that these plants are not hosts ofH. texana. While adult survival on manytest plants may imply that adult feedingoccurred, the risk to populations of theseplants in the field is negligible. It wasconcluded that H. texana is specific toProsopis spp. and could be released inAustralia for control of Prosopis spp.Observations of the biology of this speciesmade during the course of rearing andexperimentation indicated that nymphs developedthrough five instars to adults in 7–8 days sothat total development from egg to adult takes13–17 days. Females produce up to 100 eggs.     

Oviposition preference of swallowtail butterfly,Papilio polytes (Lepidoptera: Papilionidae) on four Rutaceae (Sapindales) host plant species

Abstract Oviposition preference and egg deposition site selection by the butterfly, Papilio polytes L. (Lepidoptera: Papilionidae) on four rutaceous host plants, Citrus aurantofolia (Christm.) Swing., Citrus hystrix DC., Citrus reticulata Blanco, and Murraya koenigii (L.) Sprengel, were assessed in field cages measuring 2 × 2 × 2 m. Simultaneous two-choice and four-choice oviposition tests of whole host plants were conducted. The mean total number of eggs laid per plant on C. reticulata in the two-choice test was significantly higher (P < 0.01) than those on C. aurantifolia, C. hystrix, and M. koenigii. Among the three other host plants, C. aurantifolia was preferred over C. hystrix, and M. koenigii (P < 0.01) and C. hystrix was preferred over M. koenigii (P < 0.01). In the four-choice test, C. reticulata was highly preferred and significantly different from C. hystrix and M. koenigii. However, no oviposition preference was detected with C. aurantifolia. Among the various plant parts in the two- and four-choice tests, eggs on leaves of each plant were the highest, followed by numbers on stems, and negligible numbers on pots. These numbers on leaves of C. reticulata and C. aurantifolia were not significantly different (P > 0.05), but differed significantly (P < 0.01) from those on leaves of C. hystrix and M. koenigii. The quantitative trend of egg-laying on stems was very similar to that observed for the leaves. Papilio polytes showed strong preference to lay eggs on the underside of leaves of all host plants than on the upper side or on the petiole. More eggs were laid on the upper side of each host plant than on its petiole. The four host plants in descending order of preference were C. reticulata≥C. aurantifolia > C. hystrix > M. koenigii. Although M. koenigii was the least preferred, it has the potential to serve as an alternative host plant for P. polytes which can be manipulated when necessary, to alleviate the infestation of this pest to the citrus industry.     

Two closely related species of Nipponaphis (Hemiptera: Aphididae) that migrate between Distylium racemosum and Machilus trees in Japan

Nipponaphis loochooensis Sorin, 1996 and N. machilicola (Shinji, 1941) form fig‐shaped or globular galls on Distylium racemosum in southern Japan. Nipponaphis machilicola migrates to the lauraceous evergreen Machilus thunbergii. Nipponaphis loochooensis has also been supposed to migrate to M. thunbergii, but its secondary‐host generation has not been found in the field to date. Through sampling Nipponaphis aphids from trees of M. japonica in addition to M. thunbergii, and sequencing their mitochondrial DNA, we found that the two species form colonies on twigs of both Machilus species, and that the two at times colonize on the same trees and even form mixed colonies. Only N. loochooensis forms colonies on leaves of M. japonica, but neither species colonizes on leaves of M. thunbergii. The secondary‐host generations of the two species could be clearly discriminated from each other, based on morphology. It was confirmed by examining the type specimens of Nipponaphis amamiana Takahashi, 1962 that the name is a junior synonym of N. machilicola.     

Responses of an oligophagous beetle species to rearing for several generations on alternative host‐plant species

1. Imprinting and rearing on alternative host‐plant species over several generations may affect performance and preferences of herbivorous insects. In this study, the adjustment potential to alternative hosts was investigated in the oligophagous beetle Phaedon cochleariae (F.) (Coleoptera: Chrysomelidae). 2. A population that had been reared for several generations on Brassica rapa was split and transferred to either one of the alternative Brassicaceae species, Sinapis alba and Nasturtium officinale, or was kept on B. rapa for continuous rearing. After 10 generations, a subset of the Sinapis and Nasturtium populations was tested again on the original host species, B. rapa. Larval performance and adult preferences were tested. 3. In the second generation, beetles performed better (higher body mass and faster larval development) on B. rapa than on the two alternative species. No evidence for imprinting was found. After 10 generations of selection on the alternative plant species, the performance of the beetles on these species improved. This effect was more pronounced on S. alba than on N. officinale. However, the performance on B. rapa after 10 generations of selection on the alternative species was unaffected, and was nearly equal to the insects kept continuously on B. rapa, with slight deviations only in the lines selected on N. officinale. 4. Most females preferred to oviposit on B. rapa independent of their experience, suggesting a genetic fixation and/or a positive relationship between larval performance and adult preference. Preferences may have been also driven by physical leaf characteristics.     

Bambusicolous fungi in Japan (1): four <Emphasis Type="Italic">Phaeosphaeria</Emphasis> species

Four Phaeosphaeria species on bamboos are reported. Leptosphaeria lelebae on culms of Bambusa multiplex is synonymized with P. oryzae. A Phaeosphaeria sp. on leaves of Sasa kurilensis is noted to have some similarities to Leptosphaeria sasae. Cultural characteristics of P. brevispora collected from culms of Sasa sp. are first recorded. Phaeosphaeria bambusae on leaves of Pleioblastus simoni is redescribed. In addition, the history of taxonomic studies on bambusicolous fungi in Japan is briefly reviewed.     

Frequency of occurrence of mangrove fungi from the east coast of India

This paper describes the frequency of occurrence and biodiversity of fungi from mangroves of the Godavari and Krishna deltas, on the east coast of India. Seventy three species were identified from Godavari and 67 from the Krishna mangroves. Fifty five species were common to both sites, 18 were found only at Godavari and 12 at Krishna mangroves. Verruculina enaliawas found to be very frequent at both sites with a higher frequency of occurrence at Godavari. Eutypa bathurstensis was very frequent at Godavari but only frequent at Krishna. Cirrenalia pygmea and Cryptosphaeria mangrovei were frequent at the Godavari mangrove, but were recorded occasionally at Krishna. Decaying samples of Rhizophora and Avicennia were studied in detail. Forty three species were common to both hosts, while 22 species were recorded only from Avicennia and 20 only from Rhizophora. Verruculina enalia was the only very frequent fungus recorded on both hosts with a lower percentage occurrence (14.8%) on R. apiculata as compared to Avicennia spp. (24.3%). Eutypa bathurstensis was the next most frequent fungus on Avicennia, while Rhizophila marina was next most frequent on Rhizophora. Dactylospora haliotrepha which was recorded frequently on Rhizophorawas infrequent on Avicennia.     

Food attraction and population growth of fungivorous nematodes with different fungi

Food attraction of the fungivorous nematodes Aphelenchus avenae and Aphelenchoides spp. to seven fungal species (Pyrenochaeta lycopersici, Botrytis cinerea, Rhizoctonia solani strains AG 3 and AG 2‐1, Verticillium dahliae, Pochonia bulbillosa, Mortierella hyalina and Trichoderma harzianum) was determined on agar plates by counting the number of test nematodes present on the mycelium of each fungus 24 h after inoculation. Population growth of A. avenae and Aphelenchoides spp. on five of the seven fungi included in the attraction test (P. lycopersici, R. solani strain AG 3, V. dahliae, P. bulbillosa and T. harzianum) was also determined on agar plates by counting nematode numbers every week during a 6‐week period. A. avenae and Aphelenchoides spp. were attracted to all the fungi tested. A. avenae was preferentially attracted to V. dahliae (P < 0.0001), and Aphelenchoides spp. did not show any preference except for low attraction to R. solani. A. avenae and Aphelenchoides spp. reproduced on all fungal species tested. After 6 weeks of incubation, the highest number of nematodes was found on P. lycopersici and P. bulbillosa, while the lowest number occurred on R. solani for A. avenae and on T. harzianum for Aphelenchoides spp. The suitability of a fungus as a host was not clearly related to the attraction to that fungus.     

Life history of the predatory mite <Emphasis Type="Italic">Phytoseiulus fragariae</Emphasis> on <Emphasis Type="Italic">Tetranychus evansi</Emphasis> and <Emphasis Type="Italic">Tetranychus urticae</Emphasis> (Acari: Phytoseiidae,Tetranychidae) at five temperatures

Tetranychus evansi Baker and Pritchard and Tetranychus urticae Koch (Acari: Tetranychidae) are important pests of Solanaceae in many countries. Several studies have demonstrated that T. urticae is an acceptable prey to many predatory mites, although the suitability of this prey depends on the host plant. T. evansi, has been shown to be an unfavorable prey to most predatory mites that have been tested against it. The predator Phytoseiulus fragariae Denmark and Schicha (Acari: Phytoseiidae) has been found in association with the two species in Brazil. The objective of this work was to compare biological parameters of P. fragariae on T. evansi and on T. urticae as prey. The study was conducted under laboratory conditions at 10, 15, 20, 25 and 30°C. At all temperatures, survivorship was lower on T. evansi than on T. urticae. No predator reached adulthood at 10°C on the former species; even on the latter species, only about 36% of the predators reached adulthood at 10°C. For both prey, in general, duration of each life stage was shorter, total fecundity was lower and intrinsic rate of population increase (r _m ) was higher with increasing temperatures. The slower rate of development of P. fragariae on T. evansi resulted in a slightly higher thermal requirement (103.9 degree-days) on that prey than on T. urticae (97.1 degree-days). The values of net reproduction rate (R ₀), intrinsic rate of increase (r _m ) and finite rate of increase (λ) were significantly higher on T. urticae, indicating faster population increase of the predator on this prey species. The highest value of r _m of the predator was 0.154 and 0.337 female per female per day on T. evansi and on T. urticae, respectively. The results suggested that P. fragariae cannot be considered a good predator of T. evansi.     

Effects of Bacillus thuringiensis δ-endotoxins Cry1Ab and Cry1Ac on the coccinellid beetle,Cheilomenes sexmaculatus (Coleoptera,Coccinellidae) under direct and indirect exposure conditions

Genes encoding cry1Ab and cry1Ac δ-endotoxins from the bacterium, Bacillus thuringiensis (Bt) that have been incorporated in several crops to enhance their resistance to insect pests may possibly influence the activity and abundance of natural enemies of insect pests. The ladybird beetle, Cheilomenes sexmaculatus (L.) might ingest Bt toxins expressed by genetically modified plants by feeding on aphids, early instar larvae of lepidopterans, and other soft bodied insects feeding on transgenic plants. Therefore, we studied the effects of Cry1Ab and Cry1Ac Bt toxins on C. sexmaculatus under direct and indirect exposure conditions. For direct exposure, the neonate C. sexmaculatus larvae were fed either pure 2M sucrose (control) or sucrose solution containing Cry1Ab or Cry1Ac (0.1%), and on alternate days with aphids till pupation. Direct exposure of C. sexmaculatus larvae to Bt toxins resulted in reduced larval survival and adult emergence as compared to the controls, which might be due to long-term direct exposure. However, there were no adverse effects of the Bt toxins on C. sexmaculatus when the larvae were reared on Aphis craccivora Koch fed on different concentrations of Cry1Ab or Cry1Ac in the artificial diet. A significant and positive correlation was observed between the presence of Bt toxins in aphids, and coccinellid larvae and adults (r=0.53** to 0.86**). The results suggested that a direct exposure to Bt toxins expressed in transgenic plants or predation on H. armigera on Bt-transgenic plants will have little effect on the activity and abundance of the ladybird, C. sexmaculatus.     

Three ascomycetes on leaves of evergreen Ilex trees from Japan: Rhytisma ilicis-integrae sp. nov., R. ilicis-latifoliae, and R. ilicis-pedunculosae sp. nov.

Three species belonging to the genus Rhytisma causing tar spot were collected on leaves in evergreen trees of Ilex species from Japan. Rhytisma ilicis-latifoliae, the known species, is found on Ilex latifolia, and R. ilicis-integrae sp. nov. and R. ilicis-pedunculosae sp. nov. are found on I. integra and I. pedunculosa, respectively. Ascomata are formed on the abaxial part of the stromata in all the Rhytisma species studied, and spermogonia are formed on the amphigenous parts in R. ilicis-latifoliae and on the adaxial part in R. ilicis-integrae and R. ilicis-pedunculosae. Shape and size of asci, ascospores, and spermatia are distinctly different among the three species. The morphology of germination tubes from ascospores and appressoria is unique for each Rhytisma species. Yellowish spots arise on the newly developing leaves in mid-May, then abundant spermatia are produced in spermogonia in the three Rhytisma species. In the next year, ascospores are produced in ascomata from early April to late May in R. ilicis-integrae and from early April to early June in R. ilicis-latifoliae and R. ilicis-pedunculosae, and they are considered to be the inocula of disease infection.     

Suitability of the biomass crop Miscanthus sinensis as a host for the aphids Rhopalosiphum padi (L.) and Rhopalosiphum maidis (F.), and its susceptibility to the plant luteovirus Barley Yellow Dwarf Virus

1 The reproductive performance of two aphid pest species, Rhopalosiphum padi and Rhopalosiphum maidis, was investigated on two seedling growth stages of Miscanthus sinensis, rhizomatous M. sinensis‘Giganteus’ and barley. Rhopalosiphum padi was unable to complete its development on Miscanthus. Rhopalosiphum maidis was most fecund on rhizomatous plants compared with seedling stages. 2 The ability of R. maidis to transmit the RPV isolate of Barley Yellow Dwarf Virus (BYDV) to M. sinensis seedlings was further investigated. Following successful transmission, host plant symptomology and the effect of infection on the yield of Miscanthus were investigated. Total above soil biomass was reduced by around 23% following infection. 3 The inability of R. padi to utilize Miscanthus is reviewed in light of this species’ origin and inability to utilize C₄ host plants. 4 The potential pest status of R. maidis on Miscanthus is discussed together with the impact that Miscanthus cultivation could have on the ecology of this aphid species and BYDV in the U.K.