Studies on Ulmus: VII. Essex Elms

This biometrical study is based on a collection of nearly 500leaf samples from every ancient parish in the county. Most ofthe elms could be assigned to one of nineteen groups, 9 of U.carpinifolia, 1 of U. glabra, 2 of U. procera, 3 of putativeF₁ U. carpinifolia x U. glabra, 3 of U. carpinifolia with suspectedintrogression from U. glabra, and 1 of U. carpinifolia x U.procera. U. glabra is indigenous. Most of the U. carpinifolia appearto have spread out from six centres of origin, mostly near thecoast. These elms are very similar to forms now occurring innorth-west France, and it is thought probable that they wereintroduced from there, possibly by the settlers responsiblefor the Red Hills salt workings shortly before the Roman occupation.One group of U. carpinifolia came from Cambridgeshire via theEssex branch of the river Cam. Of the two main populations ofU. procera, that characteristic of south-east Essex is believedto have come from northern Kent, probably from the Hoo peninsula,while the group found in south-west Essex is probably a laterintroduction from further west. Hybridization between introduced U. carpinifolia and nativeU. glabra has occurred on a very large scale and putative F₁hybrids extend in a broad band across the county from the Hertfordshireborder to Suffolk. This hybridization most likely occurred duringthe clearing of the heavily forested part of northern Essexin pre-Conquest times. Subsequently, back crossing occurredbetween these hybrids and U. carpinifolia. Occasional hybridizationalso seems to have occurred between U. procera and the othertwo species. An outline of the probable history of the elm in eastern Englandas a whole concludes the paper.     

Studies on Ulmus: VI. Fenland Elms

A biometrical study of the leaves of the elms of the Isle ofEly and of the Parts of Holland, Lincolnshire, is presented.The number of samples totalled seventy. Elms are sparsely distributedin the Fenland except in the Island of Ely. Most of the samplespertain to one of four groups of U. carpinifolia, to U. procera,to U. glabra or to the Dutch Elm. No type of elm is believedto be indigenous in the area. The only elms likely to be ofancient standing are two of the groups of U. carpinifolia inthe Island of Ely, one of which was probably introduced fromthe Cam valley and the other from Huntingdonshire about theRoman era. The mosaic of elm types in the northern Fens arebelieved to be much more recent, in many cases post-medieval;some of these, as at Thorney, were probably introduced as seedfrom the continent.     

The elms of Wales

Two methods of biometrical analysis were used to characterizea collection of 178 leaf samples assembled in the course ofan all-Wales survey of elms made in 1977–78. All sampleswere referable to either U. glabra, U. minor var. minor, U.minor var. vulgaris (= U. procera)orU. x hollandica. The variationwithin each taxon is described. Elm regions are demarcated tosupplement those already described for England. U. glabra isthe only elm believed to-be native. It is thought most likelythat the main Welsh population of U. minor var. vulgaris, inGlamorgan, was introduced from Somerset some time before theNorman Conquest. U. minor var. minor is rare throughout Walesand could be of 18th century origin; its possible spread alongdrovers' routes is considered. Some notomorphs of U. x hollandicamust have been introduced as such. Others probably arose inWales from hybridization involving U. glabra, U. minor var.vulgaris and U.x hollandica var. hollandica.     

Effects of Ophiostoma ulmi and Ophiostoma novo-ulmi culture filtrates on elm cultures from genotypes with different susceptibility to Dutch elm disease

Cell cultures of callus tissue cultures obtained from four elm genotypes (Ulmus minor; Ulmus minor×Ulmus pumila; [Ulmus carpinifolia×Ulmus glabra] × [Ulmus wallichiana×Ulmus glabra]; and Ulmus pumila), either susceptible or resistant to Dutch elm disease (DED) were exposed to culture filtrates of Ophiostoma ulmi and Ophiostoma novo-ulmi. Elm cells were largely affected by crude culture filtrate incorporated into the media. However, the correlation between ‘in vivo’ cell resistance and growth in the presence of culture filtrate was poor: the effects of fungal media components were greater than that exerted by fungal exotoxins. Therefore, it is concluded that these ‘in vitro’ assays cannot be used to evaluate resistance sources to DED in elms, or to assess specific pathogenicity of fungal isolates.     

Die mogliche Verbreitung des »UImensterbens« durch Wurzel-verwachsungen bei Ulmus carpinifolia Gled.

Possible spread of »elm disease« in Ulmus carpinifolia Gled. through root grafts . In a stand of elms (Ulmus carpinifolia Gled.), nearly all the trees were joined in groups of various sizes by “connecting roots”.     

Variation among Italian and French elm clones in their response to Ophiostoma novo‐ulmi inoculation

In 1995 a clone bank of elms from across Italy was created at Antella (Florence, I) under a European Union project. In 1998 an experimental planting of some clones from this source was established in Antella together with material from a similar clone bank in France and two reference clones: Commelin (relatively susceptible) and Lobel (relatively resistant). In May 2001, the elms were inoculated with Ophiostoma novo‐ulmi and disease development was assessed throughout that summer and the next. Significant differences in susceptibility were found between taxonomic groups, with putative natural hybrids between Ulmus minor and Ulmus pumila being the most resistant and Ulmus glabra the most susceptible. Significant differences were also found within U. minor, some clones being as resistant as Lobel. For U. minor, a statistically significant relation was found with latitude, southerly clones showing less disease than more northerly ones. Relationships were also found between disease severity and times to bud burst, these relationships applying both to the different taxonomic groups and within U. minor. Relationships between growth increment and disease severity were inconsistent. These results are discussed in relation to the intrinsic genetically‐controlled differences that exist between elms and to differences in susceptibility that occur as the growing season proceeds and as a consequence of environmental influences.     

Oviposition preference and larval performance of Aeolesthes sarta (Coleoptera: Cerambycidae) in six hardwood tree species

Sarta longhorned beetle (SLB), Aeolesthes sarta Solsky, is an economically important pest of fruit and shade trees in central and east Asia. Choice, no-choice, and larval insertion experiments were conducted to determine SLB oviposition preference and larval host suitability on six hardwood tree species including Ulmus carpinifolia Borkh., Ulmus carpinifolia var. umbraculifera Rehd., Platanus orientalis L., Populus alba L., Salix alba L., and Fraxinus rotundifolia Miller subsp. persica (Boiss.), under laboratory conditions. In the choice and no-choice experiments, significantly greater numbers of eggs and living larvae, and greater mass of living larvae were found on U. carpinifolia and U. carpinifolia var. umbraculifera compared to those on the other tree species. In the choice experiment, oviposition did not occur on F. rotundifolia subsp. persica. There were a few eggs on P. alba but no living larvae. The mean mass of living larvae was lowest on P. orientalis. In addition, in the no-choice experiment significantly fewer numbers and mass of living larvae were found in P. alba and F. rotundifolia subsp. persica. In the larval insertion experiment, more larvae survived on U. carpinifolia and U. carpinifolia var. umbraculifera compared to the other trees. Larvae recovered from U. carpinifolia and U. carpinifolia var. umbraculifera weighed significantly more than larvae from the other trees. These results suggest that U. carpinifolia and U. carpinifolia var. umbraculifera are the most preferred and suitable hosts for SLB adults and larvae. Salix alba is an acceptable host for adult oviposition and a potentially suitable host for larval development. Platanus orientalis and P. alba are less suitable, and F. rotundifolia subsp. persica appeared to be unsuitable as a host for SLB.     

Colonization of Two Nothofagus species by Lepidoptera in Southern Britain

Between 1975 and 1982 a study was made of the invertebrate faunacolonizing two deciduous species of southern beech, Nothofagusobliqua and N. procera, introduced into Britain from South America.Special attention was paid to the folivorous larvae of Lepidopterawhich were sampled at 15 localities in southern England, mostlyin Forestry Commission trial plots and arboreta in Gloucestershire. The literature describing the native insect fauna of Nothofagusin Chile and Argentina is briefly reviewed. Mention is alsomade of the few previous records of lepidopterous larvae observedfeeding on Nothofagus in Britain. The larvae of 81 species Lepidoptera are recorded from Nothofagus.Seventy-eight of these were feeding on the foliage, of which73 were found on N. procera and 62 on N. obliqua, although approximately62 per cent of all the larvae collected were from N. obliqua.Faunal differences between the sites studied are briefly described.Two additional species of cutworm larvae are also reported attackingthe roots of Nothofagus seedlings. The changing lepidopterous fauna on Nothofagus from May untilSeptember is described and discussed. Spring-feeding larvaeof Operophtera brumata (L.), Agriopis aurantiaria (Hübn.)and Erannis defoliaria (Clerck) comprised 55 per cent of alllarvae collected on the two hosts, and represented between 68per cent and 87 per cent of those larvae in beating samplescollected in late May and early June. Most of the larvae collected were reared to adult in the laboratoryon a diet of Nothofagus leaves. The majority of these are regardedas polyphagus species although 64 are known to have one of thetwo native Quercus as a host-plant, while 24 have been recordedas feeding on Fagus sylvatica. The relevance of these two generaas sources for the Lepidoptera fauna colonizing Nothofagus isdiscussed. Nothofagus obliqua and N. procera are shown to have acquireda substantial lepidopterous fauna since their introduction intoBritain near the beginning of this century, although most ofthe trees sampled were less than 25 years old. These two speciesof Nothofagus may be vulnerable to defoliation by several speciesof caterpillar, especially if planted as monocultures in areaswhere oak and beech are plentiful. However, their surprisinglylarge insect fauna may be seen to have some value for natureconservation purposes.     

Some Consequences of the 1975-1976 Drought for Dutch Elm Disease in Southern England

During the exceptionally hot, dry summer of 1976 the large elmbark beetle, Scolytus scolytus, was able to invade and successfullybreed in apparently healthy, undiseased elms. A conspicuousfeature was the clustering of wasps, bees and ladybirds on thestems, attracted by sap exudation. The trees were probably sufferingfrom drought, although many showed no symptoms. The phenomenonoccurred mainly on shallow soils over limestone; trees on chalkwere not generally affected. In 1976, and to some extent in 1975, the downward developmentof Ceratocystis ulmi through the tree was less than in previousyears, and only a low proportion of the numerous maturationfeeding wounds became infected. However the drought does notappear to have significantly influenced the course of the epidemic. The attacks by S. scolytus on undiseased trees are discussedin respect of 19th Century reports of attacks on elms, and itis concluded that the ability of S. scolytus to assume a moreprimary role may have been underestimated.     

Winter Frost Hardiness of two Chilean Provenances of Nothofagus procera in Scotland

The frost hardiness of the shoots of individual trees withintwo Chilean provenances of Nothofagus procera (Poepp & Endl.)Oerst. was measured once in each of the months January, February,November and December 1989 and January and February 1990. Therewere significant (P<0.05) differences of frost hardinessbetween provenances but only one tree could be shown to be significantlymore frost hardy than the others within the same provenance.During the winter of 1989/90 both provenances were hardy toabout –14°C (temperature killing 50 per cent of shoots)in December, but the shoots dehardened to about –9°Cin January before hardening again in February. This patternof alternate hardening and dehardening seemed to mirror changesin air temperature and could render N. procera liable to frostdamage where (as happened in 1988/9 in the UK) mild spells occurin winter followed by severe frosts.     

Metabolic fingerprinting allows discrimination between Ulmus pumila and U. minor,and between U. minor clones of different susceptibility to Dutch elm disease

Experiments were conducted to test whether Fourier transform‐infrared (FT‐IR) spectroscopy, coupled with chemometric methods, can distinguish healthy xylem tissues collected from elms known to differ significantly in their susceptibility to Ophiostoma novo‐ulmi Brasier. Twig samples from resistant Ulmus pumila L., susceptible U. minor Mill. and resistant U. minor clones were harvested on 1 May, 15 May, 1 June, 1 July and 1 September 2004, and subjected to FT‐IR analysis. The application of principal component analysis to the spectral data, followed by discriminant function analysis, discriminated between the three groups of samples in all harvesting dates. The examination of the DF‐loading plots allowed the identification of key regions within the spectra for the separation between clusters. The chemical assignments of these key regions allowed the following interpretations to be made: (i) U. pumila tissues contained enhanced levels of starch, cellulose and lignin with respect to U. minor tissues and (ii) resistant U. minor tissues contained enhanced levels of starch, cellulose and pectic polysaccharides with respect to susceptible U. minor tissues. The possible roles of the compositional differences in disease resistance, as well as the potential use of FT‐IR spectroscopy and chemometrics as a tool for screening resistant elms are discussed.     

Frost hardening and dehardening in Abies procera and other conifers under differing temperature regimes and warm-spell treatments

Frequent bud frost damage in cultivation of Abies procera Rehderand pending climate changes are the background for this studyof cold hardiness under varying acclimation regime (in closed-topchambers) and experimental warm spells during the cold season.LT₅₀ values were established by freezing tests at differenttimes of year. Damage and deaths were assessed on leader buds,subapical lateral buds, needles and cambium. Minor parallelexperiments involved Abies nordmanniana, Picea abies and Piceasitchensis. Lower acclimation temperatures resulted in deeperfrost hardiness during late autumn but less during spring, comparedwith ambient temperature controls. Elevated temperatures resultedin less deep frost resistance. Apical buds generally developeddeeper frost hardiness than lateral buds but less deep thanthe cambium, varying with species, however. Frost damage inbuds ranged from death over partially destroyed bud contentsresulting in distorted shoots to buds seemingly remaining dormant.Responses to warm spells differed with duration, timing andspecies, ranging from dramatic decrease in frost hardiness withor without subsequent recovery to no reaction. Furthermore,the reactions did not show any clear relation to dormancy level.For A. procera, exposure to fluctuating temperatures appearedto be particularly problematic. This explains why this speciesdevelops best in coastal climates, and in sites sheltered fromtemperature extremes either by hedging, a winter snow cover,or topography. The Christmas tree production will suffer severelyon sites with harsh temperatures due to losses of lateral andterminal buds, which destroy the crown symmetry. Clipping ofgreenery is less influenced by frost damages, although the developmentof normal branch whorls is often disturbed.     

First report on the Dutch elm disease pathogen Ophiostoma novo‐ulmi from Latvia

During 2017, Dutch elm disease was investigated on 67 Ulmus glabra and 29 Ulmus laevis samples from 28 sites in Latvia. The presence of Ophiostoma novo‐ulmi was detected in 61.2% of the samples from U. glabra and in 34.5% of the samples from U. laevis. In 11% of cases, hybrids between subsp. novo‐ulmi and subsp. americana were identified, particularly in the sites in the southern part of Latvia. This study presents the first verified record of Ophiostoma novo‐ulmi and its subspecies in Latvia.     

Testing Dosage Rates of Methoxychlor Applied by Helicopter for Control of Dutch Elm Disease

During April 1973 various doses and concentrations of methoxychlorwere applied to healthy elms by helicopter on farmland nearWarwick. Bioassays showed that only the highest rate, five gallonsof 6 per cent methoxychlor per tree achieved good control ofmaturation feeding by Scolytus scolytus (Fab.) for six weeksafter spraying. The bioassays indicated that the efficacy ofthis treatment declined markedly between six and ten weeks afterspraying. None of the treatments prevented beetle-borne infectionofthe treated test elms, though trees sprayed with five gallonsof 6 per cent methoxychlor showed the least amount of Dutchelm disease at the end of the summer Separate tests of aerial spray deposits using a standard quantityof methoxychlor at varying dilutions in water showed that treecoverage was generally good, though none of these treatmentssatisfactorily controlled elm beetle maturation feeding. Residueanalyses of methoxychlor deposits indicate that the originalresidues declined by about 50 per cent thirteen weeks afterspraying     

Xylem vessel diameter as a factor in resistance of Ulmus minor to Ophiostoma novo‐ulmi

An investigation has been carried out to study the relationship between the susceptibility of Ulmus minor to Ophiostoma novo‐ulmi and the diameter of its xylem vessels. Vessel diameters have been analysed in seven Spanish elms of known susceptibility, taking measurements from second and third year rings in 3‐year‐old branches. In the second year rings no relationship could be observed between the vessel diameters and the susceptibility of the trees. In the third year rings the mean diameter and the percentage of vessels larger than 100 μm were found to be significantly greater for the group of elms of high susceptibility. In the third year rings the vessel transectional area (VTA) and the theoretical hydraulic conductance (THC) were calculated. The decrease in VTA and THC became increasingly noticeable in the group of high susceptibility elms as vessels of larger diameter were excluded from the calculation. Xylem vessel diameters and the proportion of large vessels were correlated with the susceptibility of U. minor to Dutch elm disease. How these properties influence the dispersal of the fungus, the sap flow and the tree's ability to compartmentalize the disease is discussed.     

Field observations on the biocontrol of Dutch elm disease with Trichoderma virie pellets

Fifteen elm trees ranging in DBH from 25 to 40 cm were inoculated with ca. 8 mm diameter pellets containing propagules of Trichoderma viride IMI 206039 and IMI 2006040 besides nutrients. These pellets were inserted in the trunks every 10 cm around the circumference. Dead elms present upwind and downwind from the 15 treated elms remained standing during the four year duration of the experiment. No progress in the disease occurred during three growing seasons after the original treatment. During the fourth growing season (1982) 4 elms died and 11 survived, though one was severely damaged. These 11 surviving trees were retreated in September 1982.     

Studies on multipurpose fodder trees and shrubs in West Africa: variation in determinants of forage quality in Albizia and Paraserianthes species

We investigated variation in forage production, in sacco dry matter (DM) and nitrogen (N) degradations, and in vitro gas production characteristics of four Albizia (A. lebbeck N 864, A. procera N 865, A. saman N 825) and Paraserianthes falcataria (N 783) provenances obtained from The Nitrogen Fixing Tree Association. After one year of establishment forage production was assessed by harvesting trees at 0.5 m above ground in the main wet (April–August) minor-wet (September–November) and dry (December–March) seasons at Ibadan, southwestern Nigeria. Forage samples from the main-wet and dry seasons were incubated for 6, 12, 48, 72 and 96 h in rumen-fistulated cattle to estimate in sacco DM and N degradation characteristics. In vitro gas production was estimated over 3, 6, 12, 24, 48, 72 and 96 h of incubation. Forage production of A. procera was significantly higher than the other species in all seasons. Cell-wall components were comparatively higher in A. procera than the other species. Potential DM and N degradations of A. lebbeck and A. saman were significantly higher than P. falcataria and A. procera. The results suggest that A. lebbeck and A. saman provenances used in this study have relatively higher feed value than A. procera and P. falcataria.     

Diversity and pathogenicity of Botryosphaeriaceae on declining Ostrya carpinifolia in Slovenia and Italy following extreme weather conditions

Unusual and extensive dieback of European hop hornbeam (Ostrya carpinifolia) has been observed in western Slovenia and northern Italy in recent years, when extreme drought and higher temperatures were recorded. A preliminary study identified Botryosphaeria dothidea as a potential causative agent of the dieback. Further characterization of intra- and interspecies diversity of Botryosphaeriaceae collected from O. carpinifolia and other tree species in the affected area was achieved based on anamorph morphology, sequence data from the ITS rDNA and EF1-??, PCR?CRFLP analysis and AFLP profiles. The majority of the isolates analyzed were identified as B. dothidea, and in vitro pathogenicity tests re-confirmed the fungus to be an important cause of the disease. Insight into the B. dothidea population, diversity based on AFLP markers indicates that the dieback observed in O. carpinifolia is probably associated with a heterogenous population of B. dothidea, which emerged from a latent state in response to changed climate conditions. Isolates with Dothiorella-like conidia were also identified during the survey, but these were collected more rarely and appear to represent undescribed species. Isolates from Dothiorella genus expressed low pathogenicity in pathogenicity tests and proved no impact on the pathogenic ability of B. dothidea.     

Woodland Elms in Wessex

A study undertaken by the Wessex Silvicultural Group on thegrowth of elm in woodland disclosed the occurrence of potentiallyvaluable elm stands in many parts of south-west England. Thepaper discusses some aspects of cultivating elm in woodland,and provisional estimates of volume production are made. Muchof the information relates to English elm (Ulmus procera Salisbury),but other species and hybrids are briefly reviewed. Commentson some current elm problems are included.     

Further studies on pathogenicity in Ceratocystis ulmi1

Inoculation experiments on Ulmus procera, U. glabra and U. pumila with isolates of Ceratocystis ulmi from Canada, the United States, England, France, the Netherlands and Iran confirmed earlier work on the correlation between cultural characters and pathogenicity. Inocula-