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     

Beech in Wessex - a Perspective on Present Health and Silviculture

The condition of beech (Fagus sylvatica L) growing in thirtywoods in the south of England is described. In older woods,up to 20 per cent of trees were killed or seriously damagedby the summer drought of 1976. Most surviving trees have recoveredfully. Beech snap disease, associated with the fungus Nectria coccineais widespread in younger stands, especially those also affectedby lime-induced chlorosis, beech scale (Cryptococcus fagisuga)or severe competition. Nevertheless, sufficient trees surviveto provide a choice of final crop. In the long term, beech doesnot seem likely to die out through drought or disease. Trees of almost all ages and conditions exhibit a tendency tomultiple forking. The principle remedy is to keep trees in closedcanopy until a 6 to 8 m clean bole has been obtained. Beechresponds well to heavy thinning at this stage. The long term future of beech woodlands depends on timber valuesand on support for their ecological and amenity value. Silviculturally,beech is the best adapted species for the shallowest calcareoussoils, especially on the Jurassic limestone.     

Field Attraction of Scolytus scolytus (F.) to the Enantiomers of 4-Methyl-3-heptanol, the Major Component of the Aggregation Pheromone

The attraction of Scolytus scolytus (F.) to the four enantiomersof 4-methyl-3-heptanol, the major component of the aggregationpheromone, was studied in the field. Only the (–)–threoisomer attracted significantly more beetles than the blank (control),and the response to this isomer was not significantly differentfrom the response to commercial 4-methyl-3-heptanol, which containsall four isomers. There was no evidence for inhibition of attractionby the other three isomers. Commercial 4-methyl-3-heptanol couldtherefore be used, in combination with other components of theaggregation pheromone, for population sampling and control bymass trapping of S. scolytus.     

STUDIES ON ULMUS: III. The Village Elms of Hertfordshire

A biometrical study of the elms of southern Cambridgeshire waspublished in Forestry, xxxi. 132. The present paper is a parallelstudy of the village elms of Hertfordshire. The number of samplescollected was 143. For each of these, 8 quantitative and 1 qualitativefoliar character were determined. The majority of the samplesfall into 9 biometrically defined groups, 7 pertaining to U.carpinifolia and 2 to U. procera. U. glabra was also encounteredand one putative hybrid between U. glabra and U. carpinifolia. The U. carpinifolia elms occur in the east of the county andappear to be of Roman introduction in at least one case. Ofthe two groups of U. procera, one with short petioles and lowbasal asymmetry is centred around St. Albans. The other group,with longer petioles and conspicuous basal asymmetry, appearsto have entered the county both from the Icknield zone in thenorth and from Middlesex in the south. Both groups of U. procerawere established by the end of the Middle Ages, but their introductioninto the county has not yet been closely dated.     

Effects of drought on beech in Lady Park Wood, an unmanaged mixed deciduous woodland

The effects over 16 years of the 1976 drought on the beech (Fagussylvatica L.) population in mature, mixed deciduous, semi-naturalstands in Lady Park Wood are described. Individual trees wererecorded within sample transects at intervals from 1945 onwards,so it was also possible to examine responses in relation toprevious growth. Many mature beeches were killed immediatelyor severly damaged. Growth of survivors was negligible untilabout 1985 and never recovered to pre-drought rates. Damagedtrees were still dying 15 years later from drought-induced damage.Sub-canopy beech in those parts of the wood which suffered mostcanopy mortality grew rapidly after 1983. Through its effectson beech, the drought had a marked impact on the structure andsuccessional trajectory of the wood     

Temporal Trends in Twig Growth of Fagus sylvatica L. and their Relationships with Environmental Factors

Dendrochronology and twig growth studies provide useful historicalinformation about tree growth and permit analyses of the effectsof measured environmental parameters on such growth. Recentgrowth histories of currently healthy and unhealthy beech {Fagussylvatica L.) trees were reconstructed for a number of sitesin southern England, by measuring annual twig extension growthback to 1960. The relationships between twig growth and a numberof climatic (and one pollution) variables were then determined,using multiple regression analyses. A substantial reduction in twig growth was found in 1976 and1977 for all trees, indicating the dramatic effect of the severedrought that was experienced throughout much of southern Englandduring 1976. After this time, healthy trees at all sites quicklyregained their pre-1976 growth rates. In contrast, unhealthytrees at two sites failed to recover and still show greatlyreduced rates of growth. At two additional sites, while theeffect of the 1976 drought is clear, the growth rates of unhealthytrees have been significantly lower than their healthy neighbourssince before 1960. Soil type and tree age failed to providean adequate explanation for the lower than expected growth ratesof unhealthy trees seen at almost all sites. At most sites, a significant proportion of the variance in twiggrowth is explained by combinations of climatic variables. Inmost such cases, growth rates decreased as the variable concernedincreased. Ozone was included in the best fit model for unhealthytrees at two sites. However, since this pollutant accountedfor only a small amount of the model variance and the ozonedata were of poor spatial resolution, care must be taken overthe interpretation of this result.     

Dutch elm disease pathogen transmission by the banded elm bark beetle Scolytus schevyrewi

Dutch Elm Disease (DED) is a vascular wilt disease of Ulmus species (elms) incited in North America primarily by the exotic fungus Ophiostoma novo‐ulmi. The pathogen is transmitted via root grafts and elm bark beetle vectors, including the native North American elm bark beetle, Hylurgopinus rufipes and the exotic smaller European elm bark beetle, Scolytus multistriatus. The banded elm bark beetle, Scolytus schevyrewi, is an exotic Asian bark beetle that is now apparently the dominant elm bark beetle in the Rocky Mountain region of the USA. It is not known if S. schevyrewi will have an equivalent vector competence or if management recommendations need to be updated. Thus the study objectives were to: (i) determine the type and size of wounds made by adult S. schevyrewi on branches of Ulmus americana and (ii) determine if adult S. schevyrewi can transfer the pathogen to American elms during maturation feeding. To determine the DED vectoring capability of S. schevyrewi, newly emerged adults were infested with spores of Ophiostoma novo‐ulmi and then placed with either in‐vivo or in‐vitro branches of American elm trees. The inoculation of trees via feeding wounds was successful 30% of the time for in‐vivo trials and 33% for in‐vitro trials. Although the infection rate of DED has declined in Colorado over the past 10 years, the disease is still present in urban elms. While it appears that S. schevyrewi is another vector of the DED pathogens, it appears that S. schevyrewi is no more efficient than S. multistriatus. Thus, management programs that remove elm bark beetle breeding sites, rapidly remove DED‐infected elms and include the planting of DED‐resistant elms should continue to be effective management tactics.     

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.     

Infection by Armillaria mellea and some Factors Affecting Host Resistance and the Severity of Disease

Infection by A. mellea in Britain occurs by means of rhizomorphs;the transfer of mycelium at root contacts is probably not importantas a means of spread. Following the initial phase of rhizomorphpenetration, established infection in the cambium is precededby ectotrophic spread of mycelium in the bark scales. Field investigation confirmed reports in the literature thatin susceptible conifers the greatest number of deaths generallyoccurs approximately 6–8 years after planting. However,attacks can also occur in much older crops and the reasons forthis are discussed. Inoculation experiments showed that suppressed trees and thoseexperiencing conditions of reduced light intensity are moresusceptible to infection than dominant trees and trees in fulllight. Species susceptibility in a variety of soils was studiedby inoculation of trees 20–30 cm tall. Of the coniferstested Pseudotsuga menziesii and Abies grandis were more resistantthan Picea abies, P. sitchensis, Larix kaempferi and Pinus sylvestris.Quercus robur and Fagus sylvatica were more resistant than allthe conifers except A. grandis. Soil type influenced diseasedevelopment and the proportion of trees infected was higherin an acidic sand soil than in an alkaline clay soil.     

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.     

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.     

Dutch elm disease on the island of Gotland: monitoring disease vector and combat measures

The island of Gotland (Sweden) possesses the largest (more than one million trees) wild population of elms in northern Europe, which until recently was not affected by Dutch elm disease (DED). In 2005, DED was observed for the first time in the northeastern part of Gotland, and in the following years, it rapidly spread in all directions, generally following the major distribution of elms. Implementation of intensive control measures including ground surveys and geographic information system mapping of DED-diseased trees, their felling and destruction, and stump treatment with the herbicide glyphosate allowed reduction of the source of infection and probably suppression of an otherwise very rapid spread of the disease. Monitoring the flying periods of Scolytus multistriatus vector beetles between the years 2007 and 2011 showed that the abundance of trapped beetles in most cases differed significantly among individual years. Over the entire monitoring period, 55.2% of the beetles were trapped in June, 31.2% in July and 13.5% in August (difference among individual months significant at p?S. multistriatus, suggesting that the removal of trees attacked in the previous vegetation period as a combat measure should be completed before the beginning of the flying season of S. multistriatus, and that the application of the integrated DED management has the potential to arrest the development of the disease in a geographically isolated area such as Gotland.     

DAMAGE CAUSED BY SQUIRRELS IN FORESTRY COMMISSION AREAS, 1954-6

The paper examines the replies received from foresters of theForestry Commissionto questionnaires sent out at the author'ssuggestion in 1954, 1955, and 1956 on the damage caused to ForestryCommission woodlands by the two squirrels, Sciurus carolinensisand S. vulgaris leucourus, during the forest years 1954–6.The inquiry was primarily concerned with S. carolinensis, thegrey squirrel, for the killing of which rewards have been offeredsince 1953, ut, for 1955 and 1956, information was sought alsoabout the red squirrel. The most serious economic damage doneby both squirrels is considered to be the stripping of barkfrom the stemsof growing trees and it is this damage which isexamined. The information received is sifted critically andthe results summarized in thirteen tables andin two diagrams.     

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.     

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.     

Root anchorage and stem strength of black spruce (Picea mariana) trees in regular and irregular stands

A tree winching experiment was conducted, simulating wind actionand resulting damage, in order to assess mechanical resistanceof black spruce (Picea mariana (Mill.) B.S.P.) trees in standsof regular and irregular structures. The critical bending moment(M_c) of winched trees was determined and the relationship betweenM_c and tree and stand characteristics was investigated throughstatistical analyses. Stem mass (SW), average spacing betweentrees (S) and height:diameter ratio (H/d.b.h.) were initiallyselected by a screening procedure to predict M_c. Potential differencesbetween stand structures were tested in mixed models using differentsubsets of the data. Included fixed effects varied between thedifferent models. SW was the most useful and significant variablein all models and H/d.b.h. was significant only when snappedtrees were included in the analysis. When decayed samples wereexcluded, resistance to uprooting was higher in irregular stands.Decay seemed to play an important role in irregular stands andshould be investigated further. Since no difference was observedin the relationship between stem mass and critical turning momentbetween distant sites, relationships should be applicable acrosswide regions. This study provides some of the basic relationshipsrequired to model windthrow risk in irregular stands. However,the effects of stand structure on wind load for individual treeswill also need to be considered.     

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”.     

A Possible Indicator of Shake in Oak: Relationship between Flushing Dates and Vessel Sizes

Previous work by Savill (1986) has shown that oak trees (Quercusrobur and Q. petraea) with large earlywood vessels appear tohave a much greater predisposition to shake than trees withsmaller vessels. The aim of the investigation described herewas to determine whether there are any externally visible characteristicscorrelated with vessel size, so that shake-prone trees can berecognized in the field. It was found that trees that flushlatest within a population tend to have the biggest vessels.Possible reasons for this correlation are discussed briefly.The finding has the practical value that oaks which are predisposedto shake can be marked at flushing time and removed in thinningoperations.     

Distribution of the Green Spruce Needle Miner Epinotia nanana Treitschke (Lepidoptera: Tortricidae) within and between Trees at Redesdale, Northumberland

Differences were observed in the intensities of infestationof E. nanana on crops of Norway and Sitka spruce of differentages at Redesdale Forest, Northumberland. Attacks were moreserious in stands on northerly aspects. Norway spruce was moreintensely infested than was Sitka spruce, attacks being moresevere in older stands. Attacks occurred more frequently onsuppressed and subdominant trees. The intensity of infestationincreased progressively with increasing height of foliage upto 3.5 m above ground level. Attack occurred preferentiallyon current and 1-year-old needles. Continental experience withthis pest suggests that the risk of cumulative long-term damageis slight.