Gambar halaman
PDF
ePub

vine regions of the southern departments were visited from below Bordeaux to the Italian line. A portion of this same region was again visited upon his return from Algeria. From France he entered Italy, and after first briefly visiting the vineyards and many of the leading scientists of northern and central Italy, Naples was chosen as a center of work for the South. The diseases of the province of Naples and adjoining provinces had his attention for upwards of seven weeks. From Naples he passed to Sicily, continuing the work at Messina, Catania, and Syracuse, and in the western portion of the island at Palermo, Marsala, and Trapani. Those regions where Mal Nero has done its worst work received most of his time.

From Marsala, in southwest Sicily, steamer was taken for Pantelleria and Tunis. Some 600 or 700 miles of travel were made through the regency of Tunis and departments of Constantine and Algiers. Several stops were made in the vine-growing sections.

His trip comprises over 15,000 miles of travel, and that portion bordering the Mediterranean was full of interest to the pathologist and fruit grower. Numerous diseases not yet known in America were encountered, and American affections were observed under new and very interesting conditions. Many facts of interest and value to the fruit grower have been collected, more especially to Californians, as the climate and flora of the two regions are quite similar. A report embodying the results of Mr. Pierce's investigations up to the present time is now being prepared, and it is hoped to have it in the hands of the printer within a few months.

In addition to Mr. Pierce's work an extended series of experiments were made by me in Washington with a view of determining the contagious or noncontagious nature of the disease. Healthy Muscat of Alexandria grapes were obtained from New York and inoculated in various ways with diseased material from California. The most common method of procedure in this work was to graft diseased Muscat wood upon healthy roots of the same variety. Other methods, such as inarching diseased and healthy canes, planting healthy vines in soil obtained in California from around dead and dying roots, etc., were tried, but in no case was any positive evidence of the transmissibility of the disease obtained. A peculiar fact noted in connection with these investigations was that nearly all of the diseased vines recovered as soon as they were placed in the open air. In the greenhouse, however, they never made a continuously healthy growth, but I attribute this largely to the fact that the roots being in pots were crowded, hence did not perform their functions normally. As further proof of this, healthy plants treated in the same way behaved exactly like those from California.

Along with the foregoing there was made a series of bacteriolog. ical investigations, something over three hundred cultures being made from various parts of diseased vines. While some evidence of a promising nature was obtained as a result of this work, the facts accumulated are not suflicient to warrant me in making any positive statements.

SPECIAL SUBJECTS. Summaries are given below of three papers prepared by my assistant, Miss E. A. Southworth, to appear in full in THE JOURNAL OF MYCOLOGY. The subjects are of considerable economic importance, especially the anthracnose of cotton which threatens to be a troublesome disease.

HOLLYHOCK ANTHRACNOSE.

Colletotrichum malvarum (A. Br. & Casp.) South.

[Plate I.]

This is a disease which has been known to tlorists only five or six years. It is especially destructive to seedlings under glass, but attacks outdoor plants as well; and wherever it makes its appearance destroys a large part or all of the crop. It has quadrupled the price of hollyhocks in New York City in the last three years, and has nearly put an end to growing them for ornamental purposes in the Government grounds. The disease is caused by a parasitic fungus, which may live in any part of the plant. If it attacks the lower portion of the stem, as it is almost sure to do in time, it runs down to the root and kiils the plant.

In order to gain all possible information as to the conditions which were favorable, or otherwise, to the life of the fungus causing the disease, a circular of inquiry was sent to some prominent florists. The answers revealed the following facts: (1) Greenhouse plants are more susceptible than others to the disease; (2) putting diseased plants out of doors sometimes checks the disease ; (3) heat and moisture favor the development of the fungus.

An experiment in the use of Bordeaux mixture and ammoniacal copper carbonate as preventives of the disease was made in a large New York greenhouse. The results were only moderately satisfactory. Very little effect was observed from the ammoniacal solution, but the lot treated with Bordeaux mixture was much more vigorous and was much more free from the fungus than the unsprayed. The foreman of the greenhouses was so encouraged by the results that he decided to spray the plants out of doors as well.

ANTHRACNOSE OF COTTON.

Colletotrichum gossypii, South.

[Plate II.] This disease was first brought to our notice in 1888; and since that time we have received many complaints and inquiries concerning it. It is especially destructive to the bolls, which it attacks before they are ready to open, stopping their growth, causing them to crack open, thus exposing theimmature cotton fiber to the action of rain and dew and to the attacks of insects. Under these circumstances the cotton decays and the crop suffers accordingly. In this way our correspondents report that they lose from 10 to 25 per cent of their crops.

The effects described are found to be due to the action of a parasitic fungus very closely resembling the one causing the hollyhock disease. It has beon found to possess great vitality, being able to live for weeks in the heated air of a laboratory. The spores produced by the fungus have also been shown to be capable of producing the disease in a healthy boll; both facts pointing to the necessity of removing disease plants from the field, and of practicing rotation of crops. Plans are being made to test the value of fungicides for this disease during the next cotton-growing season. The mode of growing cotton renders it possible to apply fungicides rapidly and economically; and an intelligent cotton-grower, who has suffered some loss from the disease, has generously offered his assistance in field experiments having this object in view. It is therefore hoped that by another year we shall have something definite in the way of preventing the disease.

RIPE ROT OF GRAPES AND APPLES.

Glæosporium fructigenum, Berk.

[Plate III.]

The Annual Report for 1887 contained a full account of what was then called “bitter rot of apples." About two years ago a fungus very like the one causing this disease wàs found on the grape. The fungus was carefully studied and it was ascertained that spores from the grape would produce bitter rot on the apple, and vice versa that spores from the bitter rot of apples would produce the fungus and consequent decay in the grape. In the latter, however, the rotting grapes do not have the bitter taste characteristic in the apple.

These facts give rise to a confusion in regard to the name the disease which is common to the grape and apple. “Bitter rot” will not apply to the disease of the grape. "Anthracnose” is preëmpted, otherwise this might be used, as the fungus belongs to the same type as the one causing the grape anthracnose. The term “ ripe rot” may answer the purpose in spite of its lack of euphony, as the disease attacks neither apples nor grapes until they begin to ripen.

The fungus seems to be slowly gaining a foothold on the grape, and in some parts of the country causes the grapes to rot after they are carried to the packing houses. Experiments have shown that is easily controlled by fungicides, but there is great danger in the fact that it is already widespread on the apple, and wherever it is present on this fruit the grape is not secure from it.

EXPLANATION OF PLATES.

PLATE I.--HOLLYHOCK ANTHRACNOSE.

Figs. 1 and 2. Diseased plants.
FIG. 3. Fruit of fungus.
Fig. 4. Spores: a, c, normal; b, germinating.

PLATE II.-ANTHRACNOSE OF COTTON.

Figs. 1 and 2. Diseased bolls.
FIG. 3. Fruit of fungus.
FIG. 4. Successive stages in formation of spores in artificial cultures.
Fig. 5. Spores.

PLATE III.-RIPE Rot or GRAPES AND APPLES.

FIG. 1. Diseased grapes.
Fig. 2. Diseased apple.
FIG. 3. Fruit of fungus.
FIG. 4. Spores.

FIG. 5. Germinating spores, producing secondary spores at a, b, c; b, secondary spore germinating.

[graphic][graphic]
« SebelumnyaLanjutkan »