Ulmus Laevis Research Articles

POLYPHENOLS AND DISCOLORATION IN THE ELM DISEASE INVESTIGATED BY HISTOCHEMICAL TECHNIQUES

Discoloration was produced in the xylem of seedlings of white elm (Ulmus americana) by injection of ethanol and buffer solutions; this was similar to the discoloration produced in elms infected by Ceratocystis ulmi. Histological changes produced during infection were studied. The distribution of polyphenols in healthy and diseased elms was compared by histochemical tests; the strong reaction in cells that in later stages of infection showed browning is an indication that pathological discoloration is due to oxidized phenolic compounds. These may originate by synthesis or by degradation of existing substances. Their role in the disease development may be to interfere with the sap movement either by their action on living cells or by their participation in the occlusion of vessels, and they may act also as toxins.

HISTOCHEMICAL STUDIES ON THE ALTERATION OF LIGNIN AND PECTIC SUBSTANCES IN WHITE ELM INFECTED BY CERATOCYSTIS ULMI

Histochemical tests were performed on sections from 3- and 4-year-old seedlings of white elm (Ulmus americana) artificially inoculated with Ceratocystis ulmi in studies on alteration of lignin and of pectic substances following infection. Results showed more intense reactions to tests for lignin and pectins in sections from diseased elms than in sections from healthy elms. Lignin and pectin positive materials were found in vessel plugs. It is suggested that these alterations of lignin and pectins result from the action on cell walls of pectolytic enzymes produced by the pathogen.

Structure, Formation, and Dormancy of Terminal Buds of Elm

Extension growth in red elm (Ulmus rubra Muhl.) and in white elm (U. americana L.) is normally terminated in both seedlings and mature trees by abortion and abscission of the shoot tip. Subsequent growth is from subjacent axillary buds and produces a sympodial axis. Terminal buds are formed on a few glasshouse-grown seedlings and saplings, the progeny of trees from the Lincoln, Nebraska, region, and on still fewer field-grown seedlings. Terminal buds have not been observed on saplings or mature trees in this region. Abscission of shoot tips bearing terminal buds may be similar to normal abortion of elongating shoot tips, but more commonly renewed growth produces a monopodial axis. Terminal buds differ structurally from elongating shoot tips in that the stipules of leaves at the lower nodes mature while development of the blades, petioles, and subtending internodes is arrested. Bud scales occurring one at a node are found in axillary buds but are absent from terminal buds. The paired basal stipules of terminal buds function as bud scales by inclosing the distal portions of the shoot tip. Terminal buds are formed more commonly on seedlings exposed to daily photoperiods of 8 hr or less and on seedlings that retain the opposite-leaf arrangement at the end of extension growth. Bud dormancy was studied by defoliation and chilling treatments. Terminal buds and pseudoterminal axillary buds are similar in that following the end of extension growth a state of correlated inhibition exists which is followed by a state of rest.

THE PERIOD OF SUSCEPTIBILITY OF ULMUS AMERICANA TO CERATOCYSTIS ULMI UNDER CONDITIONS PREVAILING IN QUEBEC

The results of an experiment performed for the first time in 1946 and repeated the next 3 years shows that proneness of 10- to 13-year-old white elms to infection by C. ulmi was high from May 15 to late July in Quebec. However, successful inoculations were obtained each year on trees inoculated before and after (as late as November) that period. The time at which susceptibility reached its maximum, which was some time between the end of May and late June, depended on weather conditions. Wilting was suppressed during periods of dry weather.

RECHERCHES SUR LA RÉSISTANCE DE L'ORME D'AMÉRIQUE AU CERATOCYSTIS ULMI

The selection conducted at L'Assomption, P.Q., from 1950 to 1963, has confirmed the very high susceptibility of the white elm (Ulmus americana L.) to the attack of Ceratocystis ulmi (Buis.) C. Moreau and the absence of resistant strains in nature. Thermal neutrons or X-ray treatment of seeds has not appreciably modified seedlings reaction to infection, except in 4 cases out of almost 150,000 in which no symptoms were apparent before the fifth annual inoculation or more. One individual has resisted nine consecutive tests and its cuttings did not take the infection after two assays. Resulting from a mutation produced by X-rays, this vigorous clone has a normal foliage but is of a smaller size than other elms of the same age. This case of immunity in the white elm is related to that of the Asiatic species and certain European strains also of slow-growing habit and resistant.

The Byron Bog in Southwestern Ontario

The Byron Bog lies within the city limits of the City of London in southwestern Ontario. It is a relic bog lying about 300 miles south of the forested region of Ontario in which bogs are prevalent. It lies in the northern border of the Carolinian Zone.The wooded slopes around the bog include trees characteristic of southern Ontario, including White Elm, Bur Oak, Hackberry, Silver Maple, Black Cherry and Choke Cherry. The slopes encircle a zone of damp woods with Alder Buckthorn, White Pine, White Birch, Larch, Black Spruce with an undergrowth of Purple Chokeberry, Huckleberry, Blueberry and Leather-leaf.

Insect Enemies of Lecanium coryli L. (Homoptera: Coccoidea) in Saskatchewan

Local outbreaks of Lecanium coryli L. on white elm, Ulmus americana L., at Indian Head and Regina, Saskatchewan, were investigated from 1957 to 1960. Information on the seasonal occurrence, habits of the females, natural mortality, and chemical control of the scale has been reported (Peterson, 1960). During this investigation, data on insects attacking the scale were collected and are presented in this paper. Eleven species of hymenopterous parasites and one dipterous predator were collected. All were associated with the late nymphal stage and/or the adult stage of the female host. Table I lists the hymenopterous species and shows the numbers of adults and their emergence periods, recorded from 1958 to 1960.

HISTORY OF THE DUTCH ELM DISEASE IN THE PROVINCE OF QUEBEC, CANADA

The first cases of the Dutch elm disease in Canada were recorded in 1944 in the Province of Quebec, but there is evidence that the causal organism was introduced around Sorel before 1940. In 20 years the disease has extended over more than half the range of the white elm in the Province, or about 25,000 square miles, with an average rate of spread of some 1,200 square miles per year. Observations in 6 one-square-mile areas during a 13-year period indicate that between 5 and 30 per cent, or an average of 16 per cent, of the elm trees were killed by this disease. On this basis the Dutch elm disease has killed at least 600,000 trees during its 20-year history in Quebec. The relative density of elm trees appears to be the main factor which has determined the intensity and pattern of attack.

The Distribution, Life History, and Economic Importance of the Winter Moth, Operophtera brumata (L.) (Lepidoptera, Geometridae) in Nova Scotia

In the early 1930's defoliation of red oak, Quercus rubra L., white elm, Ulmus americana L., apple, Malus spp., and other deciduous trees in the South Shore region of Nova Scotia was attributed to the fall cankerworm, Alsophila pometaria (Harr.), and the spring cankerworm, Paleacrita vernata (Peck). The identity of the latter was questioned when adults occurred in the fall. These adults were sutbsequently identified as Operophtera brumata (L.), the winter moth (Hawboldt and Cuming, 1950; Smith, 1950).

THE HEMICELLULOSE OF WHITE ELM (ULMUS AMERICANA) II. CONSTITUTION OF THE METHYL GLUCURONO-XYLAN

The wood of white elm (Ulmusamericana) has been found to contain less xylan than most other hardwoods. Partial hydrolysis of the hemicellulose component yielded an aldotriouronic acid, a glucuronosyl xylose, 2-O-(4-O-methyl-α-D-glucopyranosyluronic acid)-D-xylopyranose, 4-O-methyl-D-glucuronic acid, and galacturonic acid.Hydrolysis of the fully methylated polysaccharide gave a mixture of 2-O- and 3-O-methyl-D-xylose, 2,3-di-O-methyl-D-xylose, 2,3,4-tri-O-methyl-D-xylose, and 2-O-(2,3,4-tri-O-methyl-α-D-glucopyranosyluronic acid)-3-O-methyl-D-xylopyranose in a molar ratio of 6:124:1:14. The number-average degree of polymerization of the methylated hemicellulose was 133 and that of the native polymer 185. On the basis of this and other evidence it is suggested that the xylan is linear and contains 185 1,4-linked β-D-xylopyranose residues, every seventh of which carries a single terminal side chain of 4-O-methyl-D-glucuronic acid attached by an α-glycosidic bond through C2 of the xylose. The number of acid groups is larger than in other hardwood hemicelluloses so far studied.

A Note on the Association of Fall Cankerworm (Alsophila pometaria (Harr.)) with Winter Moth (Operophtera brumata (Linn.)) (Lepidoptera: Geometridae)

The fall cankerworm, Alsophila pometaria (Harr.), and the winter moth, Operophtera brumata (Linn.), both feed to a great extent on the same tree species and prefer apple, Malus spp., red oak, Quercus rubra L., basswood, Tilia spp., white elm, Ulmus americana L., and Norway maple, Acer platanoides L. They also have similar life-histories and habits (Smith 1950 and 1953). Both lay their eggs on the trees in the fall and overwinter in this stage. The eggs hatch about the same time and the larvae of (both species mature about the third week in June. They drop to the ground and form cocoons at a depth of about an inch. The adults emerge about the same time, commencing usually during the last week in October and continuing until early December or until the ground freezes.

THE HEMICELLULOSE OF WHITE ELM (ULMUS AMERICANA): I. IDENTIFICATION OF 2-O-(4-O-METHYL-D-GLUCOPYRANOSYLURONIC ACID)-D-XYLOPYRANOSE

Alkaline extraction of wood meal from white elm (Ulmus americana) has yielded a hemicellulose which on hydrolysis gave a sugar mixture containing xylose together with traces of galactose, glucose, mannose, and rhamnose in addition to two monouronic acids and one aldobiouronic acid. The latter was identified as 2-O-(4-O-methyl-D-glucopyranosyluronic acid)-D-xylopyranose.

LOW TEMPERATURE INJURY TO ROOTS OF WHITE ELM

White elms (Ulmus americana L.) failed to leaf properly at Saskatoon, Saskatchewan, in the spring of 1950 following unusually cold weather in January. Although precipitation in 1949 and the first six months of 1950 was well above average, the symptoms were characteristic of moisture deficiency. Trees on cultivated ground and trees whose growth rate was below average suffered most. On the basis of symptoms, climatic records, and ecological conditions it is concluded that the above-ground symptoms were a result of the killing of roots by unusually low winter temperatures. The occurrence of this injury provides a good example of difficulties that may be encountered when introduced trees are not completely adapted to the environment.

Breeding and establishing new trees resistant to disease

While the vanished American chestnut has not yet been replaced by blight-resistant chestnuts, or white pines, elms and poplars saved from the ravages of other diseases, great advances have been made toward achieving these goals.

OCCURRENCE OF THE ELM LEAF BEETLE, GALERUCELLA XANTHOMELAENA (SCHR.), AT ST. CATHARINES, ONTARIO

In July 11, 1945, in the city of St. Catharines, Ontario, while looking for some elm trees reported by Dutch elm disease scouts as being severely leaf-eaten, I found two white elms (Ulmus americana L.) carrying large numbers of coleopterous larvae which were at once taken to be referable to the elm leaf beetle, Galerucella xanthomelaena (Schr.)

An Annotated List of the Birds of Rooks County, Kansas, and Vicinity

The following annotated list of birds is the result of ten years of study and observation in Rooks, Ellis, and Graham counties. For comparison with the records in these counties, studies were also made in Geary, Logan, and Scott counties. The most extensive work was done in Rooks county in 1935 and 1936, in the vicinity of Stockton. Much time was spent in observing and collecting along the south fork of the Solomon river, which runs within a few hundred yards of Stockton on the southwest. Many field trips were taken into the upland prairies. The Solomon river flows east through Rooks county. Its course is marked through most of this county by a winding strip of timber. The principal trees are cottonwood and white elm. The bottomland of this stream averages about one half mile in width. It is largely in cultivation. There are scattered strips, some of them over one fourth mile in width, that are too sandy to farm. Some of this sandy area consists of dunes, where the vegetation is scant and is made up principally of plum brush and prickly pears, with a few scattered hackberry and ash trees. The bluffs bordering the stream rise abruptly on the south to a maximum height of 160 feet above the river. On the north they are of about the same average height, but are not so steep. These bluffs are underlaid with limestone, which crops out along the rims. They are too rocky and rough to cultivate and are nearly all in little bluestem (Andropogon scoparius), which is used for grazing. Above the rims and on the upland prairies buffalo grass (Buchloe dactyloides) is the principal cover where the land is not in cultivation. The bluffs are cut by ravines in which scrubby white elm, ash, and hackberry trees are found (fig. 1). Golden eagles roost in these trees in the winter, while bald eagles are common locally, in the taller trees along the river (fig. 2). Most of the land back of the bluffs is in cultivation and is quite level. There are few trees here excepting those planted around the farm sites and occasional timber claims (fig. 3). The principal crops are wheat, corn, kafir, and cane.