Impact of the leaf miner <Emphasis Type="Italic">Cameraria ohridella</Emphasis> on whole-plant photosynthetic productivity of <Emphasis Type="Italic">Aesculus hippocastanum</Emphasis>: insights from a model

The leaf miner Cameraria ohridella causes premature defoliation of Aesculus hippocastanum trees. In order to assess the whole-plant loss of productivity caused by the parasite, we monitored seasonal changes of leaf gas exchange and leaf area losses in horse chestnut trees freely infested or chemically treated to prevent moth infestation (controls). Data were integrated in a model and the annual loss of net primary productivity (NPP) was calculated for infested trees with respect to controls. Measurements showed marked vertical stratification of C. ohridella attacks, with lower crown strata being more infested than higher ones. Leaf gas exchange was maximum between May and early June, but it strongly decreased starting from mid-June even in controls. Model calculations showed that NPP loss of infested trees was about 30% on an annual basis (when the first moth attack is recorded at the end of April). Model simulations showed that postponing the start day of attack would have important positive effects on plants NPP. For example, if the start day of attack was postponed to 20 May, the annual loss of NPP would be about 15%. Our study suggests that A. hippocastanum trees attacked by C. ohridella are not facing serious risks of decline, especially if methods are adopted to postpone the start day of attack (e.g. removal of fallen leaves in autumn). Our data do not support the view that plants need to be totally protected from the parasite by application of insecticides.     

Effects of defoliation caused by the leaf miner<Emphasis Type="Italic"> Cameraria ohridella</Emphasis> on wood production and efficiency in<Emphasis Type="Italic"> Aesculus hippocastanum</Emphasis> growing in north-eastern Italy

The leaf miner Cameraria ohridella causes premature defoliation of Aesculus hippocastanum trees. Repeated defoliation has been reported to cause decrease in radial growth of trees and a progressive decline due to reduced production and allocation of photosynthates. Our study represents an attempt to estimate the impact of C. ohridella on annual wood increments and the hydraulic properties of the wood as well as on the dry mass of seeds. Twenty-two adult horse chestnut trees were selected, four of which had been chemically treated to prevent attack (controls). All other trees were heavily infested. The ground cover (GC) of each tree, measured from monthly hemispherical photographs, revealed that infested trees were completely defoliated in September and the slope of the GC-to-measurement dates relationship (named GC decrease index) was positively related to the number of mines per leaf. Anatomical observations showed that infested trees produced more wood per year than controls through more false rings with wider xylem conduits and, hence, with higher conductive area and theoretical flow. In fact, the theoretical flow was positively related to the defoliation intensity. In contrast, the allocation of photosynthates to seeds was strongly reduced in infested trees with respect to controls (up to 50% less). The hypothesis was advanced that horse chestnut trees reacted to C. ohridella attacks by increasing the hydraulic efficiency of the wood, thus ameliorating the water and nutrient supply to leaves between the spring and mid-summer and, therefore, compensating, at least partly, the reduced leaf lifespan.     

Biocontrol of <Emphasis Type="Italic">Cameraria ohridella</Emphasis> by insectivorous birds in different landscape contexts

The horse chestnut leaf miner (HCLM) Cameraria ohridella Deschka and Dimic (Lepidoptera, Gracillariidae) is a novel but significant pest in Europe. Current control measures are either inefficient or environmentally harmful. Tits (Parus spp.) open the mines and prey on HCLM, but the biocontrol efficiency of this behaviour has not yet been quantified. We installed bird nesting-boxes in a biennial field study on four sites close to Brunswick (Germany). On the same sites, we counted HCLM pupae, larvae, opened and closed mines, and parasitised larvae and pupae in leaves collected from horse chestnut (Aesculus hippocastanum L., Hippocastanaceae) trees with and without bird exclusion. In both years, the HCLM number and the proportion of closed mines were higher in bird exclusion trees, particularly on sites with high abundance of tits. Hence, we suggest including the facilitation of birds, particularly tits, in future HCLM biocontrol strategies.     

<Emphasis Type="Italic">Agrobacterium rhizogenes</Emphasis>-mediated DNA transfer to<Emphasis Type="Italic"> Aesculu</Emphasis>s<Emphasis Type="Italic"> hippocastanum</Emphasis> L. and the regeneration of transformed plants

Hairy roots were induced from androgenic embryos of horse chestnut (Aesculus hippocastanum L.) by infection with Agrobacterium rhizogenes strain A4GUS. Single roots were selected according to their morphology in the absence of antibiotic or herbicide resistance markers. Seventy-one putative transformed hairy root lines from independent transformation events were established. Regeneration was induced in MS liquid medium supplemented with 30 6-benzylaminopurine (BA), and the regenerants were multiplied on MS solid medium containing 10 M BA. Following elongation on MS medium supplemented with 1 M BA and 500 mg/l polyvinylpyrrolidone, the shoots were subjected to a root-inducing treatment. Stable integration of TL-DNA within the horse chestnut genome was confirmed by Southern hybridization. The copy number of transgenes was estimated to be from two to four.Communicated by E.D. Earle     

The invasive alien leaf miner Cameraria ohridella and the native tree Acer pseudoplatanus: a fatal attraction?

• 1 The horse‐chestnut leaf miner Cameraria ohridella is an invasive moth in Europe and a serious pest of horse‐chestnut Aesculus hippocastanum. The moth also occasionally attacks sycamore maple Acer pseudoplatanus, when situated beside infested horse‐chestnuts.
• 2 The main objective of the present study was to provide an overview of the relationship between C. ohridella and A. pseudoplatanus and to determine whether C. ohridella has the potential to shift to this native tree.
• 3 In the field, females oviposit on different deciduous tree species. Although less frequently attacked than A. hippocastanum, A. pseudoplatanus was clearly preferred for oviposition over 12 other woody species investigated.
• 4 Surveys in Europe demonstrated that the majority of A. pseudoplatanus trees found beside infested A. hippocastanum had mines of C. ohridella, even though more than 70% of the larvae died within the first two instars. Attack rates and development success greatly varied from site to site. Attack levels on A. pseudoplatanus were not always correlated with those on A. hippocastanum, and mines on A. pseudoplatanus were sometimes observed beside weakly‐infested A. hippocastanum.
• 5 Field observations, experimental exposure of A. pseudoplatanus saplings and rearing trials in a common garden study showed that individual trees may vary in their susceptibility to C. ohridella, whereas there was no evidence that C. ohridella populations vary in their performance on A. pseudoplatanus.
• 6 To date, there is little evidence that C. ohridella represents a major risk for A. pseudoplatanus.

     

Impact of the leaf miner Cameraria ohridella (Lepidoptera: Gracillariidae) and bleeding canker disease on horse‐chestnut: direct effects and interaction

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Effects of fruit thinning on fruit and seed features of <Emphasis Type="Italic">Cistus ladanifer</Emphasis>

Fruit and seed features are the result of reproductive allocation decisions which ultimately depend on both plant availability of resources and total number of developing fruits. In this study, we manipulated fruit load in Cistus ladanifer plants by removing 0, 25 or 75% of developing fruits. Fruit features (total fruit weight, fruit-wall weight, total seed weight per fruit and seed number per fruit) were unaffected by fruit thinning, nevertheless mean seed weight increased in treated plants independently of thinning intensity. This reduced compensation was unrelated to plant size and had no consequences on fruit predation by insects. From these results it could be suggested that not only availability of resources but also morphological constraints could affect seed size in Cistus ladanifer. On the other hand, this change in seed weight could have important consequences since in this species heavy seeds perform better after fire events but light ones are advantageous in between fire recruitments.     

Parasitism of Cameraria ohridella (Lepidoptera, Gracillariidae) in natural and artificial horse-chestnut stands in the Balkans

1 The horse‐chestnut leafminer, Cameraria ohridella Deschka & Dimic, was discovered during a mass outbreak on planted horse‐chestnut trees, Aesculus hippocastanum, near Lake Ohrid in Macedonia. However, several peculiarities in the leafminer's biology and ecology, such as its inefficient control through natural enemies, indicate that it may be of exotic origin. 2 In this study, the parasitism of C. ohridella was examined in natural and artificial horse‐chestnut stands in South‐eastern Europe. The size and composition of the parasitoid complex of natural stands was comparable with that known from artificial stands. No specialist parasitoid species were detected in any of the samples. The only parasitoid species found exclusively in natural stands during this investigation were the braconid Colastes braconius and the eulophid Chrysocharis phryne. Both are known to be polyphagous on many leafminers in Europe and C. braconius has been often recorded from C. ohridella in artificial stands in previous studies. Parasitism levels varied within the same range (3.6–21.0%) throughout the entire region, in both types of habitats. 3 These results suggest that the parasitoid complex of C. ohridella in natural and planted horse‐chestnut stands in Europe is typically that of an exotic, recently introduced leafminer. Consequently, C. ohridella is probably not indigenous in the Balkans, but has been introduced to the area of its discovery from another continent.     

Masting of rowan <Emphasis Type="Italic">Sorbus aucuparia</Emphasis> L. and consequences for the apple fruit moth <Emphasis Type="Italic">Argyresthia conjugella</Emphasis> Zeller

 Masting of rowan Sorbus aucuparia L. has been studied in 45 sites in southern Norway for 22 years. We present data on the year-to-year variation in fruit setting of rowan, and show that masting is spatially synchronous in Norway and probably all over Fennoscandia. The apple fruit moth Argyresthia conjugella Zeller is an important seed predator on rowan. We present data on the abundance of apple fruit moth in rowanberries during these years and discuss the consequences of masting and intermasting of rowan for apple fruit moth as a pest of apple. We conclude that growth and climate have little impact on flowering intensity and suggest that masting of rowan is an adaptive defense against seed predation and a new example of predator satiation: intermast years inhibit predators and prepare the rowan for the subsequent mast. Received: September 3, 2001 / Accepted: February 24, 2003     

Impact of the leaf miner<Emphasis Type="Italic"> Cameraria ohridella</Emphasis> on photosynthesis,water relations and hydraulics of<Emphasis Type="Italic"> Aesculus hippocastanum</Emphasis> leaves

The mining of leaves of Aesculus hippocastanum caused by the larvae of Cameraria ohridella leads to precocious defoliation of trees. Damage to plant productivity was estimated in terms of the photosynthetic performance as well as of leaf water relations and hydraulics of increasingly mined leaves from infested plants in comparison with the same variables measured in non-mined leaves (controls). Electron microscopy and photosynthesis measurements revealed that chloroplasts within the green portions of mined leaves were still intact and photosynthesis of these areas was close to that of non-mined leaves, i.e. damage to functional integrity of the photosynthetic system did not extend beyond the mines. Stomata below the mines were functional as they maintained their physiological kinetics but most chloroplasts in the spongy parenchyma below the mines were degraded so that a 1:1 relationship existed between photosynthesis loss and loss of leaf green areas. Leaf conductance to water vapour and transpiration rate were 60% lower in mined leaf areas but equal to controls in green portions of mined leaves. Leaf water potential was insensitive to the amount of mined leaf area and so was leaf hydraulic conductance. Anatomical observations of leaf minor veins revealed that they were structurally and functionally intact even in leaves with 90% mined surface area. Our conclusion was that the actual damage to A. hippocastanum plants in terms of loss of photosynthates and water and nutrient transport was less than that visually estimated in recent studies.     

Genetic variation of horse chestnut and red horse chestnut and trees susceptibility to Erysiphe flexuosa and Cameraria ohridella

Trees of Aesculus sp. are often present in European landscapes. Common horse chestnut and red horse chestnut are seriously damaged by the fungus Erysiphe flexuosa as well as the pest Cameraria ohridella. Both pathogen and pest have spread throughout Europe. A genetic background of trees resistance still remains unknown. The present study was undertaken to estimate genetic variation of A. hippocastanum and A.×carnea grown in urban greens and their susceptibility to powdery mildew and horse chestnut leafminer. According to obtained results both species were infected by E. flexuosa in a similar degree but there were significant differences in susceptibility of particular trees (ANOVA). C. ohridella damaged only A. hippocastanum. The correlation between age of trees and degree of infestation by pathogen and pest was not observed. The significant genetic variability between two Aesculus species was revealed by the analysis of molecular variance (AMOVA) where both the intra- and the inter-species variation were found to be significant. It was shown that 73.0% of the genetic variance was contributed by the differentiation between A. hippocastanum and A.×carnea, whereas 27.0% was partitioned within species. The medium level of genetic diversity of Aesculus spp. was determined using SRAP and RAPD analyses. The mean value of genetic similarity was equal to 0.55 for common horse chestnut and 0.98 for red horse chestnut. Among 40 polymorphic SRAP and RAPD markers 17 were associated with degree of leaf damage caused by C. ohridella.     

Reproductive attributes of <Emphasis Type="Italic">Campanula</Emphasis> populations from Mt Olympos,Greece

We studied five reproductive attributes (fruit production and volume, seed content and weight, and seed germination) of different populations of Campanula species occurring along the elevation gradient of Mt Olympos, the highest mountain of Greece (2917 m), in order to examine whether and how they change with elevation, and if there are trade-offs among them. We also studied flower and fruit (reproductive) losses and population features in order to estimate whether there might be a threat to the survival of Campanula species on Mt Olympos. The genus is represented by nine species, ranging from cosmopolitan to steno-endemic. All species were found non-autogamous, and hence they depend on pollinators for their sexual reproduction. At the genus level, there is a trade-off between seed content per fruit and seed weight. At the species level, this is manifested only for C. glomerata, which produces the heaviest seeds, far exceeding all other species, and for C. spatulata, represented on Mt Olympos by two elevation distinct subspecies. Changes of the reproductive attributes are not continuous all along the elevation gradient at the genus level nor are they monotonic at the species level. Nevertheless, upland Campanula populations (≥1500 m) produce fewer fruits per individual, containing fewer but heavier seeds than lowland populations. This indicates a transition from ‘r’ to ‘K’ strategies, from low to high elevations, respectively. The patterns of change of reproductive attributes indicate prevalence of phylogenetic over environmental constraints. Laboratory tests showed that for many populations germinability is high at 15 °C, but there are both inter- and intraspecific differences regarding temperature optima. Ecotypic variation among populations of the same species at different elevations was evident; populations from higher elevations had lower optima and vice versa. Reproductive losses, ranging from zero to over 90%, occurred mainly at the stage of fruit maturation; grazing by sheep and goats was the usual cause. Though such losses might affect the short-lived species (the annual C. sparsa and the biennial C. lingulata), which depend entirely on fruit maturation and seed dispersal for their reproduction, there does not seem to be a serious threat to the survival of Campanula species on the mountain.     

Spatial patterns and infestation processes in the horse chestnut leafminer Cameraria ohridella: a tale of two cities

Spatial patterns of the horse chestnut leafminer Cameraria ohridella Deschka & Dimic (Lepidoptera: Gracillariidae) population density was analysed in the cities of Bern and Brussels in order to explore its spatial population dynamics. The surveys were carried out in Bern in 1998 and 2000 and in Brussels in 2001 to assess population density in relation to local characteristics. In Brussels, population density was also measured using pheromone traps distributed over the city and collected twice per moth generation. A quantitative relationship was found between local population density (measured by pheromone traps and survey observations) and the amount of leaves left on the ground the previous fall. Several other factors were related to observed infestation levels: the occurrence of the pathogen Guignardia aesculi was inversely related to infestation by C. ohridella in Bern in 1998 and 2000, the number of horse chestnut trees within 800 m distance was positively related to infestation level in Bern in 2000, and the proportion of green areas within 100 m and the number of other horse chestnut trees within 2000 m were positively related to infestation levels in the 2001 Brussels survey. The pattern of infestation levels as a function of distance to potential population reservoirs suggested that C. ohridella re‐invades areas where overwintering leaves have been cleaned from refuge areas such as parks or urban forests. Our results indicate that the removal of leaves is a feasible first aid control measure to reduce moth population densities. However, leaf removal may not reduce moth densities when done improperly. In places where proper leaf removal is not feasible, other control measures are needed.     

Use of <Emphasis Type="Italic">Quercus ilex</Emphasis> subsp. <Emphasis Type="Italic">ballota</Emphasis> phenological and pollen-production data for interpreting <Emphasis Type="Italic">Quercus</Emphasis> pollen curves

Although aerobiological data are often used in phenological research as an indicator of flowering, airborne pollen concentrations are influenced by a number of factors that could affect pollen curves. This paper reports on a study of various aspects of reproductive biology in Q. ilex subsp. ballota, together with environmental factors influencing pollen release and transport, with a view of achieving reliable interpretation of Quercus pollen curves in Ourense (NW Spain). Aerobiological data were recorded from 2002 to 2004 at two sites in the province of Ourense. From 1st February to the end of the flowering period, phenological observations were carried out on 19 trees from the Q. ilex subsp. ballota population found in the Ourense area. Pollen production was calculated for the same trees. The chilling and heating requirements for triggering development were also calculated. The mean flowering period lasted 11-15 days. Reduced pollen output per catkin and, especially, a reduced number of catkins per tree in 2003 and 2004, prompted a marked decline in overall pollen production. Major differences observed in Q. ilex subsp. ballota pollen curves were attributed to the considerable influence both of weather conditions during pollination and pollen production. In years with high pollen production and weather conditions favouring pollen release, Q. ilex subsp. ballota contributed almost 10% to the total Quercus pollen curve. Around 20% of the pollen trapped was captured before or after flowering periods.     

Ectomycorrhizal characterization of an American chestnut <Emphasis Type="SmallCaps">(</Emphasis><Emphasis Type="Italic">Castanea dentata</Emphasis><Emphasis Type="SmallCaps">)</Emphasis>-dominated community in Western Wisconsin

Circa 1900, a farmer from the eastern US planted 11 American chestnut (Castanea dentata) seeds on a newly established farm near West Salem in western Wisconsin. These trees were very successful, producing a large stand of over 6,000 trees. Since this area is well outside the natural range of chestnut, these trees remained free from chestnut blight until 1987. In the West Salem stand, chestnuts are the dominant species of a mixed forest community, reminiscent of the chestnut–oak ecosystems of pre-1900 Appalachia. To identify putative mycorrhizal associates of chestnut in this unique forest, our approach was twofold: (1) an extensive fruiting body survey was conducted for four seasons that yielded approximately 100 putative mycorrhizal species and (2) a belowground molecular approach was used to generate DNA sequences of the internal transcribed spacer region from ectomycorrhizae. Unexpectedly, chestnut did not appear to be the dominant underground ectomycorrhizal-forming plant species. This study highlights the need to identify the plant host species when conducting belowground molecular-based surveys and provides preliminary identification of ectomycorrhizal fungi associated with a disjunct stand of American chestnut. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Role of domestication in shaping <Emphasis Type="Italic">Castanea sativa</Emphasis> genetic variation in Europe

The genetic structure of sweet chestnut (Castanea sativa Mill.) across Europe was assessed using 73 inter-simple sequence repeat markers to screen 1,768 individuals from 68 stands distributed across 29 sites in five European countries (Italy, France, Spain, Greece, and UK). At each site, trees were sampled from three distinct management types (domestication levels): naturalized stands, managed coppice, and grafted fruit orchards. In more than a third of the orchards, nonlocal genetic material (grafted clones) were evident, showing (as predicted) large differences from the other two domestication levels for most of the within-population genetic diversity parameters estimated. Randomly generated linkage disequilibrium analysis revealed weak though significant differences in two-locus allelic correlations between naturalized stands and coppice, suggesting that long-term management techniques may influence the genetic makeup of the populations. Multivariate analysis revealed the existence of five distinct gene pools across the study area; three were located in Greece, one on the northwestern coast of the Iberian peninsula and a large gene pool covering the rest of the Mediterranean basin. The implications of the results are discussed in relation to developing conservation strategies for chestnut genetic resources in Europe.     

Survival and growth of <Emphasis Type="Italic">Juniperus</Emphasis> seedlings in <Emphasis Type="Italic">Juniperus</Emphasis> woodlands

Juniperus woodlands are widely distributed in western North America. Few studies of seedling emergence, long-term survival, growth or mortality of the dominant Juniperus spp. in these woodlands have been carried out. Consequently, regeneration dynamics in these woodlands are poorly understood. Juniperus ashei is the dominant woody plant in the majority of woodland and savanna communities of the Edwards Plateau region in central Texas. We examined the emergence, mortality and growth of various spatial and temporal cohorts of J. ashei seedlings over an eight or nine-year period. Greatest emergence was found during the cool, mostly winter months and under the canopy of mature J. ashei trees. Emergence was significantly inversely related to temperature and significantly linearly related to rainfall, but only if the monthly rainfall and emergence were offset by one to four months. Greatest survival occurred below the J. ashei canopy, but greatest growth was at the canopy edge. Emerging seedlings were not from the current years seed crop, but from one or more previous years seed crops. Greatest mortality occurred mostly during the summer months and in the grassland habitat. There was a significant inverse logarithmic or exponential relationship between mean monthly temperature and mean monthly mortality. A large number of J. ashei seedlings or immature plants with reduced growth were found beneath the canopy of mature trees. These plants seem to serve as a seedling bank, providing the source of recruitment into the population should the overstory trees be removed. Survival of the two canopy cohorts with known emergence dates declined with time (negative exponential function) and was 1.0–3.4% after eight or nine years depending on the cohort. The pre-existing cohort seemed to have constant mortality (and presumably replacement), with about 8% of the population dying each year. Higher growth rates for seedlings were found at the edge of the established woodland canopy, which suggests that conditions in the edge habitat or possibly in canopy gaps are best for growth beyond the seedling stage.     

Synthetic Auxin 3,5,6-TPA Provokes <Emphasis Type="Italic">Citrus clementina</Emphasis> (Hort. <Emphasis Type="Italic">ex</Emphasis> Tan) Fruitlet Abscission by Reducing Photosynthate Availability

The aim of this study was to determine the effects of the synthetic auxin 3,5,6-trichloro-2-pirydiloxyacetic acid (3,5,6-TPA) on photosynthetic activity, photosynthate transport to the fruit, and fruitlet abscission to further explain the physiological basis of auxin-mediated citrus fruit thinning. Applying 15 mg l⁻¹ 3,5,6-TPA to trees during the fruit cell division stage significantly increased fruitlet abscission of Clementine mandarin. On treated trees, abnormal foliar development and photosynthetic damage were observed at the same time as 3,5,6-TPA reduced fruitlet growth rate. Briefly, treatment reduced chlorophyll and carotenoid concentrations and modified chlorophyll a fluorescence parameters, that is, reduced the quantum yield (ФPSII) of the noncyclic electron transport rate, diminished the capacity to reduce the quinone pool (photochemical quenching; q_p), and increased nonphotochemical quenching (q _N), thereby preventing the dissipation of excess excitation energy. In addition, the net photosynthetic flux (μmol CO₂ m⁻² s⁻¹) and leaf photosynthate content decreased in treated trees. As a result, the 3,5,6-TPA treatment significantly reduced the photosynthate accumulation in fruit from day 3 to day 8 after treatment, thus reducing fruitlet growth rate. Hence, treated fruitlets significantly increased ethylene production and abscised. Twenty days after treatment, chlorophyll a fluorescence parameters and fruitlet growth rate were reestablished. Accordingly, the thinning effect of 3,5,6-TPA may be due to a temporarily induced photosynthetic disorder that leads to reduction in photosynthate production and fruitlet uptake that temporarily slows its growth, triggering ethylene production and fruitlet abscission. Afterward, the remaining treated fruit overcame this effect, increased growth rate, and reached a larger size than control fruit.     

Limitations of <Emphasis Type="Italic">Neoseiulus baraki</Emphasis> and <Emphasis Type="Italic">Proctolaelaps bickleyi</Emphasis> as control agents of <Emphasis Type="Italic">Aceria guerreronis</Emphasis>

Several predatory mites have been found in association with the coconut mite, Aceria guerreronis Keifer, in northeast Brazil. However, the latter still causes damage to coconut in that region. The objectives of this work were to compare the frequencies of occurrence of Neoseiulus (Phytoseiidae) and Proctolaelaps (Melicharidae) species on standing and aborted coconuts in coastal Pernambuco State, northeast Brazil and to analyze their possible limitations as control agents of the coconut mite, based on evaluations of the restrictions they may have to access the microhabitat inhabited by the pest and their functional and reproductive responses to increasing densities of the latter. Neoseiulus baraki (Athias-Henriot) was found mostly on standing coconuts whereas Proctolaelaps bickleyi (Bram) was found mostly on aborted coconuts. Measurements of the entrance to the microhabitat occupied by the coconut mite, between the bracts and the subjacent fruit surface, showed that this different pattern of predator prevalence could be related to predator sizes, although other environmental factors could not be disregarded. Progressively higher predation rate of N. baraki was observed up to an experimental density that corresponded to 1,200 coconut mites per fruit, which is close to the average number determined in northeast Brazil, reducing slightly afterwards. Predation rate of P. bickleyi reduced consistently but slightly with increasing prey densities, but in absolute values, rates were always much higher than determined for N. baraki. The excessively high killing capacity of P. bickleyi, probably related to its high feeding requirement, may be detrimental in terms of stability. In fact, such high requirement for food suggests that P. bickleyi might not have a strong relation with the coconut mite and that the latter may not be its main food source under natural conditions. It is concluded that body sizes of both predators and the exceedingly high feeding requirement of P. bickleyi may limit their performance as control agents of the coconut mite.     

Biosynthesis and characterization of copolymer poly(3HB-<Emphasis Type="Italic">co</Emphasis>-3HV) from saponified <Emphasis Type="Italic">Jatropha curcas</Emphasis> oil by <Emphasis Type="Italic">Pseudomonas oleovorans</Emphasis>

Polyhydroxyalkanoates (PHAs) are naturally occurring biodegradable polymers with promising application in the formulation of plastic materials. PHAs are produced by numerous bacteria as energy/carbon storage materials from various substrates, including sugars and plant oils. Since these substrates compete as food sources, their use as raw material for industrial-scale production of PHA is limited. Therefore, efforts have been focused on seeking alternative sources for bacterial production of PHA. One substrate that seems to have great potential is the seed oil of Jatropha curcas plant. Among other favorable properties, J. curcas seed oil is non-edible, widely available, and can be cheaply produced. In this study, Pseudomonas oleovorans (ATCC 29347) was grown in a mineral salt medium supplemented with saponified J. curcas seed oil as the only carbon source under batch fermentation. Optimum PHA yield of 26.06% cell dry weight was achieved after 72 h. The PHA had a melting point (T _m) between 150 and 160°C. Results of polymer analyses by gas chromatography/mass spectrometry (GC/MS) identified only the methyl 3-hydroxybutanoate monomeric unit. However, electrospray ionization–time of flight mass spectroscopy (ESI–TOF MS) confirmed that the PHA was a copolymer with the characteristic HB/HV peaks at m/z 1155.49 (HB) and 1,169, 1,184–1,194 (HV). The data were further supported by¹H and ¹³C NMR analysis. Polymer analysis by gel permeation chromatography (GPC) indicated a peak molecular weight (MP) of 179,797, molecular weight (M _W) of 166,838, weight number average mass (M _n) of 131,847, and polydispersity (M _w/M _n) of 1.3. The data from this study indicate that J. curcas seed oil can be used as a substrate to produce the copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3HB-co-3HV).