Cherry leaf roll virus causing a disease of Betula spp. in the United Kingdom

A virus, serologically related to isolates of cherry leaf rollvirus (CLRV) from Prunus avium (L.) L. and Sambucus nigra L.was transmitted to a range of herbaceous plants from leavesor roots of thirty-one of forty-seven trees of Betula spp. growingat two heathland sites in Berkshire. Ageing leaves of virus-infectedindividuals which had mild chiorotic blotches or ring and linepatterns in July showed bright yellow ring and line patternsin October. In the season after B. verrucosa seedlings wereinoculated with CLRV isolates, leaves developed chlorotic ringand blotch patterns; the symptoms being similar whether theinocula were originally isolated from S. nigra, P. avium orB. verrucosa. Palisade and mesophyll cells of naturally infectedleaves of B. verrucosa contained chloroplasts in which granalorganization was appreciably less distinct than that of chloroplastsfrom virus-free leaves. In many instances, virus-infected leafcells had spherical virus-like particles about 30 mn in diametercontained within tubular structures in cell wall projections;these structures were not seen in virus-free material. An isolate of CLRV from B. verrucosa, purified from systemicallyinfected leaves of Nicotiana clevelandii Gray by ammonium sulphateprecipitation and differential centrifugation, contained twomajor components having sedimentation coefficients of 118s and130s. Each component was composed of spherical particles withdiameters in the range 26–30 nm and having buoyant densitiesin caesium chloride of 1·460 and 1·493 gm/cm³.Polyacrylamide gel electrophoresis of preparations from bothbuoyant components indicated that they each contained a singlespecies of protein whose molecular weight was in the range 53,000–54,000daltons.     

Controlling Rhododendron spp. in the Turkish Black Sea Region

Rhododendrons (Rhododendron ponticum L. and Rhododendron luteumSweet) dominate the understories of the mesic forests of theBlack Sea Region (BSR) of Turkey. They dramatically reduce forestgrowth and regeneration and local plant diversity. This paperreports the results of a large rhododendron control experimentestablished on two different sites in the western and easternBSR of Turkey 5 years after treatments (YAT). The paper alsopresents the second-year results of a second experiment in whichthe foliar herbicides of the previous experiment were testedon rhododendron at much lower rates on a western BSR site. FiveYAT, grubbing and foliar spraying were still the best rhododendroncontrol methods in the first experiment. Cut-stump sprayingprovided an intermediate level of woody control. Hand-cuttingwas ineffective on R. ponticum and did not significantly differfrom the control treatment in rhododendron basal area 5 YAT.The performance ratings of foliar triclopyr ester and imazapyrfor woody control in both experiments were rate dependent. Athigh rates ranging between 2.6 and 5.8 kg ae ha^–1, foliarimazapyr controlled both rhododendron species significantlybetter than foliar triclopyr ester in the first experiment,suggesting enhanced imazapyr translocation to the roots. Someoff-target damage was observed in the beech overstory for imazapyrat high rates. The performance ratings of these foliar herbicideswere significantly reversed in the second experiment 2 YAT,where much lower rates were used (0.3–2.0 kg ae ha^–1)than in the first experiment. Insufficient imazapyr accumulationin rhododendron roots might account for the poor impact of thisherbicide. No beech damage was apparent from any of the herbicidesin the second experiment. The low-rate foliar triclopyr esteris recommended for effective and cost-efficient rhododendroncontrol.     

Cherry Leaf Roll Virus in Juglans regia in the United Kingdom

Cherry leaf roll virus (CLRV) was detected in foliage, pollenor seeds of 43 of 113 mature/overmature Juglans regia L.; twohad foliar yellow-brown ring patterns whereas seven other infectedtrees had leaf necroses. Male catkins of a few infected treeswere malformed and blackened. Infection was rare (3/43) in the widely scattered J. regia ofnorthern England and Scotland, but commoner (40/70) in southernEngland. When J. regia seed was grown in methylbromide treated soil,six per cent (18/300) of the seedlings were symptomlessly infected.Four out of ten groups of imported seedlings were infected toa similar extent, CLRV being present in a total of 40 out of1146 trees aged five years or less. When 3 years old, CLRV infectedJ. regia were shorter and thinner than healthy seedlings. CLRV from walnut was serologically distinguishable from Betula,Prunus, Cornus and Sambucus isolates. One English walnut isolate(Ox) was distinguishable from two Italian walnut isolates. Anisolate (Sr) of CLRV obtained in Finland from Sambucus racemosaL. was antigenically distinct from S. ebulus and S. nigra isolates.     

Factors influencing tree species diversity and Betula alleghaniensis establishment in silvicultural openings

We examined the short-term effects of group-selection harvestingwith seed tree retention on the diversity, abundance and establishmentof tree seedlings in a northern hardwood forest in the UpperPeninsula of Michigan (49 openings, 20 closed canopy referencesites). Three opening sizes were examined – opening radius0.5 x canopy height (267 ± 62 m², n = 16), 0.75 x canopyheight (642 ± 85 m², n = 17) and 1.0 x canopy height(1192 ± 155 m², n = 16) (canopy height = 22 m). A singleyellow birch (Betula alleghaniensis Britt.) seed tree was retainedin the centre of each opening. Tree seedling density was significantlyhigher in the largest group-selection opening than at the closedcanopy reference sites (P < 0.05), the main factor for thiswas the increased proportion of yellow birch, red maple (Acerrubrum L.) and other minor species. Nevertheless, yellow birchwas still a minor component of the developing gap cohort, comprising5.9 per cent of the seedlings and 1.1 per cent of the saplings.Within openings, microsite variables, such as per cent coversof bare soil and coarse woody debris, were the best predictorsof yellow birch occurrence and density. Our results suggestthat microsite limitations and competing vegetation may greatlyreduce the efficacy of openings for ensuring the maintenanceof mid-tolerants.     

The tolerance of newly emerged broadleaved tree seedlings to the herbicides clopyralid, cycloxydim and metazachlor

In direct-seeded woodlands and nursery seed-beds, weeds canrapidly invade newly sown areas, leading to death or suppressionof tree seedlings. Hand weeding is usually expensive, and thesafe use of broad-spectrum contact herbicides is seldom possible.Hence in the work reported here, the tolerance of young treeseedlings to the potentially more selective, post-emergenceherbicides clopyralid, cycloxydim and metazachlor, was tested.Seedlings of Fraxinus excelsior L. (ash) with two to four expandedtrue leaves (2–4 ETL), Fagus sylvatica L. (beech) (2–4ETL), Acer pseudoplatanus L. (sycamore) (4–6 ETL), Prunusavium L. (cherry) (6–8 ETL) and Quercus robur L. (oak)(6–8 ETL) appeared to tolerate applications of cycloxydimat a rate of 0.45 kg a.i. ha^–1. Applications of 0.2 kga.i. ha^–1 clopyralid or 1.25 kg a.i. ha^–1 metazachloralso appeared to be generally tolerated, but did cause somesuppression of annual growth increment in Q. robur, P. avium,F. sylvatica and A. pseudoplatanus, particularly where repeatapplications were made to the earliest growth stages. Seedlingsurvival was unaffected by any herbicide treatment. Mixturesof all three herbicides were no more damaging than the sameherbicides applied separately. Therefore, depending on treespecies and growth stage, it appears that clopyralid could potentiallybe safely used to control a range of herbaceous weed species,metazachlor a variety of seedling or germinating weeds and cycloxydima range of established grass weed species, in direct sown woodlandsor nursery seed-beds, although further research is advisableto confirm crop safety.     

Management Effects on Biomass and Foliar Nutritive Value of <Emphasis Type="Italic">Robinia pseudoacacia</Emphasis> and <Emphasis Type="Italic">Gleditsia triacanthos</Emphasis> f. <Emphasis Type="Italic">inermis</Emphasis> in Arkansas,USA

The browse potential of black locust (Robinia pseudoacacia L.) and thornless honey locust [Gleditsia triacanthos f. inermis (L.) Zabel] has not been adequately tested. Our objective was to determine effects of fertilization and pollarding on biomass and foliar nutritive value in separate studies of black locust and thornless honey locust in Arkansas, USA. Shoots were sampled monthly for two consecutive growing seasons in 2002 and 2003 to determine foliar, shoot, and total aboveground biomass, shoot basal diameter, and foliar nutritive value (crude protein and in vitro digestibility). Black locust yielded more foliar biomass when pollarded at 50 or 100 cm and fertilized with 600 kg P ha⁻¹, than at 5 cm with or without P, averaging 3.5 Mg dry matter ha⁻¹. Black locust foliar crude protein and in vitro dry matter digestibility ( ≤ 170 and 534 g kg⁻¹, respectively) decreased as leaves aged, but still met maintenance needs for beef cattle (Bos taurus L.). Thornless honey locust had little agronomic potential because of slow establishment, low foliar yield (330 kg ha⁻¹), and a 2% reversion to undesirable thorny phenotype. Black locust should be considered for livestock browse when drought induces semi-dormancy of herbaceous forages.     

Effect of Different Forms and Rates of Nitrogen Fertiliser on the Growth of Lodgepole Pine

Application of four forms of nitrogen fertilizer each at threerates produced significant positive responses in shoot growthin a seven-year-old Pinus contorta, Dougl. stand on a deep,infertile peat in south Scotland. The response was shortlived(4 years) and was followed by a period (1–2 years) whenshoot growth fell below the control level. Form of N did notaffect the result but rate of N did and these effects are discussedwith respect to annual shoot growth, foliar N levels and shootgrowth:foliar N correlations.     

Growth and mortality in underplanted tree seedlings in response to variations in canopy closure of Norway spruce stands

Six broadleaved tree species and Picea abies (L.) Karst. wereplanted under spruce plantations of varying densities, in Sweden.Treatments included control (994 stems ha^–1), dense (538stems ha^–1), sparse (294 stems ha^–1) and gap (0stems ha^–1) overstory treatments. There was an increasein height and diameter growth from control to sparse overstorytreatment of all underplanted tree species except for ash (Fraxinusexcelsior L.) and Norway maple (Acer platanoides L.). Site conditionsmay have hampered the growth of these species, as well as wildcherry (Prunus avium L.). Both oak (Quercus robur L.) and sprucehad greater growth in the gap treatment, relative to the othertreatments. Insecticide application did not influence seedlinggrowth or survival. The performance of beech (Fagus sylvaticaL.), lime (Tilia cordata Mill.), spruce and oak was consistentwith shade tolerance ranking. Beech and lime had a very highsurvival rate, even under the densest canopy. The growth andmortality of ash, maple and wild cherry differed significantlyfrom what was expected. This experiment demonstrated significantvariation in interspecific growth and mortality between sevenplanted tree species in relation to canopy density. Correctsite and species selection is crucial when underplanting inshelterwood systems.     

Control of the Large Pine Weevil and Bark Beetles of the Genus Hylastes

Since 1968 a water-based formulation of gamma BHC (Gammacol)has largely replaced DDT as a plant-dipping treatment againstthe large pine weevil Hylobius abietis L. and Hylastes spp.beetles. With Sitka spruce in high rainfall areas, BHC at 1•6 percent is as effective as DDT at 2•5 per cent in controllingthese insects. Neither chemical has proved adequate where exceptionallyhigh populations of Hylobius occurred, though control of Hylasteshas been very good. Plants were dipped in Gammacol, and then stored in sealed polythenebags for 28 days. Provided that the plants were dried sufficientlybefore storing, they subsequently suffered only a slight reductionin height-growth but received adequate protection against beetles.This technique should enable forest nurseries to supply ready-treatedplanting stock. Chlorpyrifos (Dureban) may prove a useful alternativeto BHC.     

Acceleration of Early Growth of Seedlings and Rooted Cuttings of Quercus robur L.

The normal delays in the production of useful planting materialin tree species such as Quercus robur from both seedlings andcuttings can be overcome by growing the plants at relativelyhigh temperature and in continuous light. Top growth could befurther accelerated by application of gibberellic acid (GA3)as foliar spray. There were, however, distinct differences inresponse between seedlings (with a high root: top dry matterratio, 4:1), and freshly rooted cuttings. The latter evincedonly onefifth the seedling response, but when cuttings attainedsimilar root:top ratios, their response reached that of seedlings. GA3 treatment accelerated top growth at the expense of rootgrowth, but a root dip for 4h in 100 ppm indole-3yl-butyricacid (IBA) given to 4-month-old cuttings restored root growthto normal even with GA3 treatment. During rooting, cutting commonlybecame dormant but this was prevented by foliar GA3 sprays.Growth was further and substantially improved by inclusion ofcytokinin in such sprays (benzylandenine purine, BAP). Furtherimprovements of growth were obtained by 5% sucrose suppliedto the foliage. In field experiments, assessing ‘establishment’of seedlings and cuttings, the latter established well but after550 days still had not attained the same root:shoot ratio asseedlings. GA3 (50 ppm) again greatly promoted shoot growth,while BAP increased branching and leaf number; when given togethermaximum leaf numbers and shoot dry weight were obtained, yetroot growth remained normal. Further addition of IBA raisedshoot growth still further, but other characters measured sufferedreductions. The potential use of these findings is discussed.     

Effects of climate and management history on the distribution and growth of sycamore (Acer pseudoplatanus L.) in a southern British woodland in comparison to native competitors

Sycamore (Acer pseudoplatanus L.) is an invasive, non-nativespecies in Great Britain and its management in conservationareas is controversial. Climate change adds further uncertaintyto decision making. We investigated the role of management historyin determining present-day abundance and the effects of climaticvariability on growth, photosynthesis and phenology at WythamWoods, a UK Environmental Change Network (ECN) monitoring site.Relatively few sycamore trees were found in undisturbed ancient,semi-natural woodland and recent plantations, despite beingcommon in other areas of the site. Sycamore grew more slowlythan ash (Fraxinus excelsior L.), its principal competitor,but at a similar rate to pedunculate oak (Quercus robur L.)in the period 1993–2005. There were fewer sycamore thanash seedlings, regardless of which species dominated the canopy.Growth of sycamore was slower in dry periods than wet ones andlower photosynthetic rates were measured in canopy leaves underdry compared with wet soil conditions. This study thereforesuggests that sycamore does not present a serious threat toundisturbed ancient woodland on the site and that it may eventuallydecline in areas of the site where it competes with ash, inthe absence of disturbance. It may also decline under climatechange if summer droughts become more frequent.     

The tolerance of young trees to applications of clopyralid alone and in mixture with foliar-acting herbicides

The selective herbicide clopyralid is often used to controlcompeting Cirsium arvense in newly planted woodlands. When appliedas an overall spray at different dates in the spring (at 0.2kg acid equivalent (a.e.) ha^–1) to 10 tree species (Fraxinusexcelsior, Prunus avium, Quercus robur, Acer pseudoplatanus,Populus x canadensis cv. ‘Ghoy’, Pseudotsuga menziesii,Pinus nigra ssp. laricio, Larix kaempferi, Picea abies and Piceasitchensis) it did not reduce survival, and had little effecton growth. However, some species showed distortion of the youngestsprayed leaves or needles for several weeks after treatment,particularly F. excelsior, L. kaempferi and P. x canadensis.Sequential applications of clopyralid (first at 0.1 kg a.e.ha^–1 followed by 0.2 kg a.e. ha^–1 after 3 weeks),which are often required to control C. arvense, did not leadto increased leaf damage or growth reduction. Mixtures of clopyralidwith selective graminicides (cycloxydim at 0.45 kg active ingredient(a.i.) ha^–1; fluazifop-p-butyl at 0.38 kg a.i. ha^–1and propaquizafop at 0.15 kg a.i. ha^–1) did not causesignificant adverse effects on survival or growth of any species.If herbicides are required to control mixed stands of susceptibleproblem weeds such as C. arvense and grasses which are overtoppingyoung trees, these herbicide mixtures, applied as overall sprays,are less likely to cause damage to trees than attempts to usedirected applications of broad-spectrum foliar-acting herbicides.     

Shading Reduces both Visible and Invisible Frost Damage to Norway Spruce Seedlings in the Field

Two-year-old cuttings of Norway spruce were subjected to nightfrosts in spring on an exposed site in southern Sweden. Shadingwas used to assess the influence of sunlight on the extent ofdamage resulting from night frost. Chlorophyll fluorescencewas measured in needles in flushing shoots, and in shoots atthe stage of bud burst. The F_v:F_m ratio was significantly lowerfor plants exposed to light, compared with shaded plants onthe days following the night frost (minimum temperature –6°C).The effect was similar both in 1-year-old and current year needles.The low F_v:F_m ratios indicate damage to photosystem H, causedby an interaction between sub freezing temperatures and highlight intensity. Shading also increased the survival of flushingshoots. It is suggested that regeneration of Norway spruce onsites exposed to frost should be carried out in partial shade,for example under a shelterwood.     

Foliar herbivory and leaf traits of five native tree species in a young plantation of Central Panama

This study examined foliar herbivory on 1 year-old tree saplings planted in previously abandoned fields in central Panama. Plots (15 × 15 trees) of Anacardium excelsum (Anacardiaceae), Dalbergia retusa (Fabaceae), Pachira quinata (Malvaceae), Tabebuia rosea (Bignoniaceae), and Terminalia amazonia (Combretaceae) were tested for herbivory using leaf counts and digital image analysis. Values of foliar carbon, foliar nitrogen, specific leaf area (SLA), and leaf toughness were analyzed to describe mechanical defenses and leaf nutrients on young and mature leaves of each of these species. For all five species, less than 10% of total leaf area was found to be damaged by arthropods. Significant (P-value < 0.001) differences in herbivory were found among both the tree species and the insect feeding guilds considered: chewing, skeletonizing, mining, and leaf-rolling. On mature leaves, Anacardium excelsum had the highest amount of leaf damage (3.53%) while Dalbergia retusa exhibited the lowest herbivore damage (1.72%). Tabebuia rosea had statistically significantly higher damage than other species for young leaves caused by leaf-rolling insects (4.21% rolling of 5.55% total damage). Leaf toughness was negatively correlated with SLA and foliar N. Linear regressions showed that herbivory was positively correlated with foliar N for young leaves and negatively correlated with foliar N for mature leaves. No statistically significant relationships were found between herbivory and the mechanical properties of toughness and SLA. Overall, results from this study indicate that, as young saplings, the species evaluated did not suffer high amounts of foliar herbivory in the plantation environment.     

The effect of nitrogen supply on root growth and development in sycamore and Sitka spruce trees

Sycamore (Acer pseudoplatanus L.) and Sitka spruce (Picea sitchensis(Bong.) Carr.) were grown in sand culture in glasshouses withtwo levels of N supplied with irrigation 1.0 (deficient) and6.0 (sufficient) molNm^–3, all as NH₄NO₃. Providing trees with a sufficient N supply increased both theirabove ground growth and N content compared with the N deficientplants. Provision of the generous N supply also altered thedistribution of growth between leaves and roots, with the N-deficientplants having a higher root:leaf or root:needle ratio than thewell fertilized trees. Provision of a generous N supply stimulatedroot growth, especially at the later harvests, which was reflectedmainly in growth of the tap root in sycamore. There was an increasein both root mass and root diameter with N supply. When thegrowth of white roots was monitored using a borescope, it wasshown that there were significantly more new roots producedby the well-fertilized trees. The borescope data also showeddetail of the bimodal seasonal pattern of root growth underhigh N in Sitka spruce which related to trends in nitrogen uptake.     

Seasonal population trends of<Emphasis Type="Italic"> Liriomyza huidobrensis</Emphasis> (Blanchard, 1926) (Diptera: Agromyzidae) on cucumber (<Emphasis Type="Italic">Cucumis sativus</Emphasis> L.) in Western Turkey

Liriomyza huidobrensis (Blanchard) (Diptera: Agromyzidae) is an important pest in cucumber greenhouses in Izmir, Western Turkey. This study was carried out during the spring and autumn seasons of 1999 and 2000 in two adjacent cucumber greenhouses, each 1,000 m² in size. Population densities of adult L. huidobrensis in insecticide-treated and non-treated greenhouses were compared by using yellow sticky traps. Ten traps were placed in the non-treated greenhouse and ten traps in the insecticide-treated greenhouse. Yellow sticky traps were changed weekly and the number of flies counted in order to compare the two greenhouses. In addition to monitoring the leaf miner population, in each greenhouse 100 plants were checked and the ratio of infested plants, the ratio of infested leaves per plant and the number of mines per leaf were recorded weekly. The population density of the leaf miner was almost the same in both insecticide-treated and non-treated greenhouses. Thus, it was concluded that using yellow sticky traps will be healthier and more cost effective than using pesticides. Furthermore using pesticides is risky for the environment and the use of yellow sticky traps can easily reduce the number of pesticide applications. If yellow sticky traps are used in the greenhouse in a completely isolated environment and the appropriate insecticide is used when it is necessary, this will provide successful and integrated management against L. huidobrensis.     

Decay in Norway Spruce Caused by Stereum sanguinolentum Alb. & Schw. ex Fr. Developing from Extraction Wounds

In two stands of Norway spruce (Picea abies (L.) Karst.), plantedin 1952 and 1929 in Yair Hill Forest and Glentress Forest, BordersRegion, two per cent of the trees examined in 1983 had extractiondamage on stems and superficial roots. Extraction wounds were4 and 8 years old respectively and ranged in size from 52 to1099 cm². Infection frequency of the damaged trees was 47 percent and 54 per cent respectively. Stereum sanguinolentum wasthe most common fungus isolated, accompanied by Trichodermaviride Fr; Chaetomium cochlioides Palliser and Heterobasidionannosum (Fr.) Bref. The frequency of isolation of S. sanguinolentumincreased progressively in samples taken from the outside ofstems inwards, whereas the other microorganisms present showedthe opposite pattern. In four trees, T. viride overgrew S. sanguinolentumin the the decay columns. Positive correlations were demonstratedbetween surface area of wounds and vertical extension of decay,tree volume and decay volume, and diameter of stem at breastheight (DBH) and decay volume; whereas a negative correlationoccurred between number of growth rings per 5 cm (measured inwardsfrom the outside of the bole) and radial penetration of decay.The results confirm the importance of S. sanguinolentum as awound pathogen.     

Identification,pathogenicity and control of powdery mildew caused by Erysiphe elevata on Eucalyptus pellita in Sumatra,Indonesia

Powdery mildews are biotrophic ascomycetes that do not typically kill their hosts, but instead interfere with normal plant growth. In Indonesia, white powdery spots were observed forming on the upper part of fully developed leaves of Eucalyptus pellita planted in sand beds of a clonal nursery. Thus, this study aimed to identify the causal agent of eucalypt powdery mildew in Indonesia as well as to develop control strategies to better manage the disease. Pathogen identification was based on morphology, molecular characterization of DNA sequencing the ITS region and pathogenicity test. In addition, considering that some powdery mildews are inhibited by free moisture on leaves, efficacy of foliar watering was tested for disease control. Phylogenetic analyses showed that isolates collected from infected eucalypt plants grouped together with other sequences of the Erysiphe elevata clade with bootstrap support of 99%; a similar result was also confirmed by morphological observations. Pathogenicity of powdery mildew on eucalypt plants was confirmed through artificial inoculation, thus fulfilling the Koch's postulates. For disease control, foliar watering reduced the incidence of powdery mildew on mother plants. The reduction of the disease incidence began to be more evident at 2 weeks after trial establishment, and in the fourth week, the incidence was below 10% in all three treatments, while the control was above 20%. Therefore, we concluded that E. elevata is the causal agent of powdery mildew in Indonesia and that one application of foliar watering per week was enough to minimize the disease impact in the nursery.     

Towards exploration of plant-based ethno-medicinal knowledge of rural community: basis for biodiversity conservation in Bangladesh

Because lack of data impedes the assessment of the conservation of medicinal plants, ethno-medicinal studies are important to fill this gap. This study considered the traditional use of plants for health care by the rural communities in two forested and non-forested regions of Bangladesh. A total of 230 respondents were interviewed accompanied by field observation and voucher specimen collection. Altogether, 68 species of medicinal plants belonging to 38 families distributing over 58 genera were recorded, of which 22 species were common in both regions. Trees were the most commonly utilized growth form and leaves were the most commonly used plant part. Forests and homesteads were the major sources of medicinal plants in forested and non-forested regions, respectively. High use versatility (Relative Importance >1) was represented by 14 species; Emblica officinale L. and Allium sativum L. were the most versatile species. Forty-one individual ailments were treated with the medicinal plants recorded. The ailment categories ‘respiratory problems’ and ‘sexual problems’ received the highest score from the calculation of informants’ consensus factor (F _ic) in forested and non-forested regions, respectively. The findings could contribute in the pharmaceutical sector by directing further investigation of bio-active compounds in medicinal plants. Secondly, results could inform the clues for conservation strategies of forest resources in that region.