Bark Of Twigs Research Articles

Ceratocystis ulmi . [Descriptions of Fungi and Bacteria

Abstract A description is provided for Ceratocystis ulmi . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Ulmus spp., Zelkova serrara; U. glabra and U. americana are highly susceptible, U. procera is susceptible, while Asian elms, U. parvifolia, U. pumila and U. pumila pennato-ramosa , have marked resistance. Zelkova serrata is highly susceptible; the reactions of other species of Zelkova are not known. DISEASE: Dutch Elm Disease. GEOGRAPHICAL DISTRIBUTION: Europe (throughout, to a northern limit in central Scotland, central Norway, central Sweden. Absent from north Russia). N. America (eastern Canada, central and eastern USA) (CMI Map 36, ed. 4, 1970). TRANSMISSION: By the bark beetles Scolytus scolytus, S. multistriatus and (in N. America) by Hylurgopinus rufipes . The fungus fruits in the larval galleries and spores are carried internally and externally to young shoots where beetles emerge and migrate. Infection of the vessels, which leads to the disease, takes place during the period before breeding, when the beetles feed, cutting grooves and boring in the thin bark of twigs. Transmission by root grafts is known (15, 266) and direct infection by airborne spores is theoretically possible but does not take place under natural conditions.

Biology of Oberea schaumii (Coleoptera: Cerambycidae) in Trembling Aspen, Populus tremuloides1

The biology of Oberea schaumii LeConte in trembling aspen, Populus tremuloides Michaux, was studied in Upper Michigan and northern Wisconsin. The life cycle was determined through periodic collections of the insects from suckers and large trees, and from field rearings. Various aspects of adult behavior were learned from extended observations of adults in field cages. Eggs were usually laid on stems and twigs 5–15 mm diameter and 1–6 years old. They were deposited singly (usually) in elongate, rectangular egg niches gnawed in the bark by the female. Egg niches occurred on all aspects of vertical stems but only on the upper sides of leaning stems or side branches. The egg hatched in 14–15 days and the larva bored into the wood and then downward from the egg niche, parallel to the axis of the twig or stem. The larva widened and lengthened this tunnel throughout its development, ejecting borings to the outside through 3 ejection ports. When completed, the gallery averaged 17 cm long and 4 mm diameter. Most (77.5%) individuals required 3 yrs to complete development. Eggs were laid from late June to early August and the larvae fed for 3 summers, overwintering in the gallery. Pupation occurred from mid-May to early June of the 4th calendar year, and adults emerged during the last 3 weeks of June, 3 years after eggs were laid. Five percent emerged in 2 years and 17.5% emerged 4 years after eggs were laid. Adults fed during the day along the midribs on the under sides of leaves and on the outer bark of new shoots and older twigs. Mating was observed during the day; males and females mated more than once even on the same day. Economic loss caused by O. schaumii in natural stands was negligible.

Studies on indicator plants for citrus viruses. 1

1. Thirty two species of leguminous plants were inoculated with the sap from the young shoots of Satsuma orange showing symptoms of Satsuma dwarf. Nine species including cowpea (Vigna sinensis Endl.), asparagus bean (Vigna sesquipedalis Wight), kidney bean (Phaseolus vulgaris L.), Crotalaria spectabilis Roth, peanut (Arachis hypogaea L.), garden pea (Pisum sativum L.), Chinese milk vetch (Astragalus sinicus L.), sword bean (Canavalia gladiota DC.), and Japanese clover (Microlespedeza striata Makino) were proved to be susceptible to a virus present in the affetced trees. Two species of Chenopodiaceae and three species of Cucurbitaceae were not subject to it. The authors temporarily propose the name “Satsuma dwarf virus” to this legume infecting virus.2. Among the susceptible plants listed above, Blackeye cowpea and kidney bean (Satisfaction) showed the most characteristic symptoms. The former showed mottling and vein clearing on the leaves, and necrotic streaks on the petioles as well as on the stems. The latter also developed clear mottling and vein clearing on the foliage of most plants that were infected by sap-inoculation. These two species appear to be good indicator plants. However, retransmission from infected legume plants to Satsuma orange has not been successful in the tests so far conducted.3. Higher percentages of infection resulted when the expressed sap was buffered with about an equal volume of 0.05-0.1mol solution of K2HPO4.4. One-month old shoots of affected Satsuma orange were demonstrated to carry highly active virus in the leaves, bark and wood portions. One-year old shoots and relatively old current shoots carried active virus in the wood, but not in the bark of twigs or the leaves.

Fluorescent Dye Technique for Studying Distribution of Spray Oil Deposit on Citrus1

An oil soluble fluorescent dye was incorporated with various petroleum oils to provide a qualitative means of studying the relative deposit of the dilute oil spray mistures on various parts of grapefruit trees on exposure under ultraviolet light. This technique provided a good means of qualitative comparisons of differences in oil deposit associated with (1) the concentration of oil in the spray mixture, (2) various surfactants and (3) concentration of surfactant. The dye penetrated with the oil into the outer mesocarp of the green fruit with applications during July while less penetration was observed from those made during August. Only surface deposit appeared to have occurred on mature grapefruit held in storage from the 1959 crop. The dye penetrated into the bark of green twigs but appeared to have been deposited only on the surface of the bark of small branches. The dye appeared to have penetrated into the leaf mainly at the midrib and larger veins. Photegraphs of petroleum oil deposit on the fruit, leaves, and twigs and small branches are included.

THE STRUCTURE AND DEVELOPMENT OF A WOODY TUMOR AFFECTING PICEA GLAUCA

BECAUSE OF its unusual distribution and the light which may possibly be thrown on the general problem of tumor etiology a woody tumor (fig. 2, 3) occurring inepiphytotic numbers on Mt. -Desert Island, Maine, h'as been un,der investigation in this Laboratory for some years. The distribution and general eeelogical relations of these growths have already been reported (White and Millington, 1954). The present paper will deal with their anatomy and such indications as this anatomy may give of their development and mode of origin. MATERIALS AND METHODS.-Tumors -as observed in the field range from hardly perceptible swellings under the bark of young twigs (White and Millington, 1954), (fig. 1) to growths a meter or more in diameter (fig. 2). Tissues from tumors of various ages and from normal spruce trees were collected in formalin-acetic-acid-alcohol or in chromic acid-acetic acid-formalin (CRAF III) (Sass, 1940) fixatives, impregnated under vacuum and were either stored in 70 per cent alcohol or dehydrated and imibedded either in paraffin or celloidin. Some of the material was softened with hydrofluoric acid. Tissues were sectioned either on the rotary microtome (paraffin) or the sliding microtome (celloidin and unimbedded material). Some large tumors were sawed and sanded to bring out significant features. Where serial sections of celloidin preparations'or of materials sectioned without imbedding were required they were prepared by 'methods suggested by Professor F. Hyland3 (Hyland, 1940). Sections were stained in safranin and fast green or in safranin, fast green and hemalum (Sass, '1940). Kodak Superpanchro Press Type B film was used for the photomicrographs. OBSERVATIONS.-Gross structure.-Large tumors when sawed proved to be somewhat softer thahn nor-

MEANS OF INOCULATION OF THE DUTCH ELM DISEASE BY HYLURGOPINUS RUFIPES EICHH.

Investigations on the transmission of the Dutch elm disease were carried out during summer of 1946 in Canada, where the only known vector of the fungus is the native bark beetle, Hylurgopinus rufipes. By close observations of young elms, recently and naturally infected with Ceratostomella Ulmi, it was found that by boring tunnels through the thin bark of twigs or small branches to the cambium, the adults of this beetle can inoculate the disease to healthy trees.