or delayed application that explains how the disease can continue its course, though with diminished intensity.

As is to be expected, the condition and configuration of the land exert a great influence on the isophanes: Extensive wooded regions, or mountains on which the vine does not grow, hinder the spread of the disease, while river valleys, low-lying lands liable to floods, or those subject to mists, favour it.

As regards the meteorological factors, the temperature and the quantity and frequency of rain were recorded in every locality and for each period after the 1st of April, that is during the time in which the outbreak of mildew is possible.

Since equal intervals of time, though they lend themselves to meteorological observations, have (as the writer demonstrated by experiment) no value in connection with the life-history of mildew, because they almost always comprise days in which the weather is of the most varied and even opposite character, the writer limited himself to the factor rain, and divided the time into periods of rainy days and of dry days. He determined the average number of rainy days, the frequency of the rain, the temperature of every single locality in which mildew appeared, for all the periods both of rainy and of fine days from the 1st of April up to the date of the outbreak of the disease.

With the single averages for each isophane he calculated separately the average for that isophane during the dry periods and the rainy ones, and then for the whole period from the 1st of April up to the date of the appearance of mildew on that isophane.

By multiplying this number by the number of days that elapsed between the first of April and the date of the real outbreak of mildew, a coefficient is obtained in which each factor is represented.

This coefficient is called by the writer a bios. Though it may not have an absolute value, its practical utility cannot but be recognized. In 1911 mildew appeared on the 15th of May. Calculating the values of the bios for every isophane, the following results were obtained:

isophane I II III IV V VI VII

bios.. 631 625 522 427 405 400 256

There is thus an uninterrupted diminution in the number of the bios the further one goes from the first isophane, in which mildew broke out on the 15th of May. Admitting that the course of the weather is enough to cause the outbreak of mildew in the belt of the first isophane, when the value of the bios was 631, it may be asked at what date will the climatic conditions in the meantime prevailing in the belts of the other isophanes cause the outbreak of mildew in them? With the help of the above bios a simple arithmetical calculation shows that in respect to the first isophane mildew will appear in the

BACTERIAL

AND FUNGOID

DISEASES

OF VARIOUS

The numbers in brackets are those of the days that really passed before mildew broke out.

The same concordance between calculation and practical observation was recorded in the year 1910 and in the first half of 1912; during this latter period, in almost all the localities infested by mildew the value of the bios ranges from 600 to 650; and already in the month of May it was possible to foresee the course that the disease really took and the extent to which it spread.

Without the intention of generalizing his results, the writer concludes by expressing the wish that similar researches should be undertaken in other countries also.

69 Fungi injurious to Rice in the Philippines. See above, No. 27.

CROPS

70 - Treatment for Bremia Lactucae, Peronospora effusa and Heterosporium variabile on Vegetables (1).

SCHNEIDER, NUMA. Traitement du Meunier des Laitues et Romaines et du Mildiou des Epinards. Revue Horticole, Year 84, No. 21, pp. 493-494. Paris, Nov. 1, 1912. Lettuces and cos lettuces raised under glass after October for forcing purposes are often attacked by Bremia Lactucae (or Peronospora gangliiformis). The writer has, during some years, found that a good method of controlling this disease is to cover old forcing beds, previously broken up and levelled, with an inch or more of pulverised white wood charcoal, or twig charcoal, sowing the seeds not too deeply and covering them also with a thin layer of powdered twig charcoal. The hot-beds on to which the plants were pricked out, were also covered with a layer of powdered charcoal, which was pressed down firmly so as to keep the leaves of the plants quite away from the soil. The treatment was completed by a sulphur application on a fine day at the end of November, or in December. The same treatment can be applied to cauliflowers, raised under glass at the same season.

Dusting with sulphur has been found an efficacious remedy in the case of Peronospora effusa and Heterosporium variabile, parasites of spinach; as the first application had been removed by the rain, the process was repeated a second time, using a special bellows, and in such a manner as to reach the lower surface of the leaves.

At the time of gathering, only a very small amount of sulphur adhered to the spinach leaves, and this disappeared after they were well washed.

The necessary quantity of sulphur for the treatment is very small.

(1) See also No. 418, B. Feb. 1912.

(Ed.).

71 - Infection Experiments with Thielavia basicola on Ginseng. ROSENBAUM, J.: in Phytopathology, Vol. II, No. 5, pp. 191-196 + plates XVIII and XIX. Ithaca, October 1912.

One of the most common and serious diseases affecting ginseng has been attributed to Thielavia basicola Zopf. While several workers in different parts of the United States have observed the fungus associated with the disease, no definite inoculation experiments on this host have ever been reported.

The fungus is very widely distributed and has been associated with a wide range of hosts belonging to II entirely different families. It has been reported from Germany, Russia, Belgium, England, Italy and Korea. In the United States it has been reported from several States. In the case of ginseng, the fungus is able to attack plants of all ages, being most severe on seedlings, where it is known by the growers as "fiber rot" or "end rot." It not only attacks the roots of seedlings and older plants, but has been found causing cankers an inch or more in length on the stems. Most commonly these occur at the point where the stem emerges from the ground. These cankers at first cause a discoloration, followed by a drying and splitting of the stem in a longitudinal direction, allowing it to break over. The disease has been observed to attack the ginseng plant in soils of widely different physical characters; in many cases it seems to be just as severe on new land as on soil which has previously grown several crops.

The writer reports inoculation experiments (inoculations of seedlings; 'inoculation of ginseng in the soil; inoculations on stems) of Thielavia basicola obtained from three different hosts, namely cotton, tobacco and ginseng. The conclusions arrived at from the results are the following:

1. From comparison of cultures from different hosts on various media, from infection experiments and from measurements of spores and mycelium, it appears that the forms of Thielavia basicola Zopf found on the three different hosts, cotton, tobacco and ginseng, are identical.

2. While infection without previous injury to the ginseng or tobacco is always obtained in the case of young plants, this is apparently not the case where older plants are used.

3. The fungus is able to attack the aerial as well as the underground parts of the plant; at least this proved to be the case with ginseng.

BROOKS, CHARLES and DE MERITT, MARGARET: in Phytopathology, Vol. II, No. 5, pp. 1811901 plate. Ithaca, New York, October 1912.

The paper under review is a report upon the cause and nature of apple leaf spot and includes data and discussion in regard to inoculation experiments with various fungi, studies on different forms of Sphaeropsis malorum, and experimental work on time of infection, influence of cultivation and methods of control.

Spray injury, intense sunlight following showers, frost, and a number of different fungi, including Coniothyrium pirina (Sacc.) Sheldon (form

erly known as Phyllosticta pirina), Phyllosticta limitata Pk. and Sphaeropsis malorum Pk., have been credited with causing the disease. Inoculation experiments were made by I. M. Lewis in 1908-1909 with spores from pure cultures of Sphaeropsis malorum, Coniothyrium pirina, Coryneum foliicolum, Alternaria sp. and Fusarium sp., which had been isolated from the affected areas, but only negative results were obtained.

The writers have made a study of Sphaeropsis malorum from different sources and have isolated three strains or types that are particularly distinct. The first has broadly conical unilocular pycnidia and produces oblong spores measuring 12 X 26 to 38 p; the second strain produces egg-shaped spores measuring 14 X 23 p; the third is characterised by a distinctly multilocular pycnidium; all three forms are ostiolate. The first strain is the most common on cankered limbs, but pycnidia of the second form were found several times in such positions.

The cultures obtained from leaf spots always produced pycnidia of the first form.

Only the first form of pycnidium wes found on the fruits of apples and quinces in the field. All three forms were obtained in cultures made from spots on apples, but the first was much more common than either of the others.

From the inoculation experiments made with the three strains on the foliage and fruit, the writers conclude that: 1. The leaf spot of apples as it occurs in New Hampshire orchards may be produced by Sphaeropsis malorum Pk. and is probably largely due to that fungus. 2. Of the several strains of S. malorum which may be obtained, the large-spored form is largely responsible for the production of leaf spot. 3. Infection may occur from the time the leaves unfold till the last of August. 4. Cultivation, spraying and the removal of cankers are important in the control of the disease.

Either Bordeaux mixture or lime-sulphur is an efficient remedy for the disease; but as under New Hampshire conditions Bordeaux often injures the leaves of Baldwin and other varieties, lime-sulphur seems to be more satisfactory.

73

A new Gnomonia on Hickory Leaves.

WOLF, FREDERICK A. : in Annales Mycologici, Vol. X, No. 5, pp. 488-491 + pl. XVI. Berlin, October 1912.

Upon the leaves of the shag bark hickory (Carya ovata (Mill) K. Kock) in the vicinity of Auburn, Alabama, one finds in late summer and autumn an imperfect fungus, Gloesporium Caryae Ell. & Dearn. This fungus causes the formation of large diseased areas, 1-2 cm. in diameter, reddish-brown in colour, without a well-defined margin. In case the affected areas become confluent they exceed this measurement in extent and are irregular in outline. Minute brown pustules, the acervuli of the fungus, are present in abundance upon the lower surface of the diseased areas.

Affected leaves were collected by the writer during the autumn and put away to winter out of doors. By May 4th mature perithecia had been formed

in the areas occupied the preceding autumn by the Gloeosporium stage. Further examination showed that this perithecial stage agreed morphologically with that of the genus Gnomonia. This fungus had been cultured from both the conidial and the ascosporic stages. In order to add further proof to the identity of the two forms inoculation experiments were attempted. Inoculation upon hickory leaves with pure cultures of ascosporic material (Gnomonia stage) resulted in infection and the subsequent development of the conidial stage (Gloeosporium). These conidia, when used in turn for inoculation, resulted in the production of acervuli and conidia. Inoculation in the field with pure cultures of both the ascosporic and conidial stages, made by laying small pieces of the infected material upon the under surface of leaves, produced infection.

The new name, Gnomonia Caryae (1), is proposed for this perfect stage. Complete descriptions of both stages of the species and detailed illustrations are given.

74

Withering of the Plane Tree due to Gloeosporium nervisequum.

VOGLINO, P. Il seccume del platano.-L'Italia Agricola, Year XLIX, No. 21, pp. 508-509. + coloured plate. Piacenza, Nov. 15, 1912.

For some years past, the plane trees of the avenues of Turin and the neighbourhood have been subject to withering due to the attacks of Gloeosporium nervisequum. Hitherto, the fungus has only appeared on the leaves, which it caused to wither along the course of the primary and secondary nerves, the petiole also being affected. The infected leaves fell prematurely at the beginning of spring and the growth of the plant was completely interrupted, but only for a short time, however, for fresh leaves arose from new buds, and a change in the conditions in their environment having taken place they were immune from the attacks of the parasite. In 1912, however, the disease appeared in a more serious form, which had already been observed in other parts of Italy in 1905 and in France during the last few years.

The fungus, instead of attacking the nerves and petiole only, extended its ravages to the nodes from which the leaves arise, and where the axillary buds are formed; it spread along the bark above and below the node, penetrating into the woody tissues, where it produced many black protuberances, which contained the reproductive bodies of the parasite. The axillary buds died, the foliage in some cases was completely destroyed, while the nutrition and further growth of the tree were much impeded. If the disease made its appearance in this aggravated form for several years in succession, the trees would suffer severely.

(1) Prof. Geo. F. Atkinson, Cornell University, Ithaca, N. Y., is of the opinion that Glesporium Caryae Ell. & Dearn is identical with Discosia rugulosa B. & C.

(The Author).

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