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these are not the most abundant nor apparently the most important bacteria in soil. Technical Bulletin No. 59 deals with the nonspore-forming bacteria, showing that they are the most numerous and apparently the most active bacteria in soil, but that they are so difficult to study that it is almost impossible to identify any of them with previously described species. These organisms are considered to be so important in soil that a more intensive study of some of them and of their activity in the decomposition of organic matter in soil is now being made. The other large group of soil microorganisms, the Actinomycetes, is treated in the last paper of this series, Technical Bulletin No. 60. These organisms appear to be numerically quite important; but certain technical difficulties make it hard to tell whether or not they are very active in soil. Identification of the forms found in the soils studied has proved impossible as yet. Some of them are closely related to, if not identical with, the organism causing potato scab. The chief point emphasized by these soil flora studies is the meagerness of present-day knowledge in regard to the microorganisms of soil. One of the first steps which appears to be necessary in order to put the knowledge of soil bacteria on a scientific basis is a classification of them. The study reported in this series of bulletins is a preliminary step toward such a classification; but much work remains to be done.
Potato scab investigation. The similarity between certain soil Actinomycetes and the organism causing potato scab has led some soil investigators to believe the cause of this disease to be widespread in soil. If it is a very common soil organism the control of the disease must be based upon different principles from those in general practice. To test out this matter an investigation has been begun this year in coöperation with the Botanical Department of the University of Illinois, but results are not yet ready for publication.
The direct microscopic examination of bacteria in soil.-- A method has been worked out for examining the bacteria of soil directly under the microscope. This is quite similar to the method already used for studying milk bacteria microscopically, but the development of a satisfactory technic has proved more difficult. The method used and a few of the most interesting results obtained with it are shortly to be published as a technical bulletin.
COÖPERATIVE STUDIES. Potato scab investigations.
Department Botany, University of
Illinois. Stable and milk sanitation ..
Illinois Agricultural Experiment Station. Methods of counting bacteria in milk.. State College of Agriculture, Ithaca,
White Springs Farm Dairy Company.
dairymen in the vicinity of Geneva.
Blackheart and the aeration of potatoes in storage.--- The peculiar behavior of some potato tubers in an air-tight jar led to an investigation of the effect of scant aeration upon potatoes in storage. The results of this work are given in Bulletin No. 436.
It was learned that potatoes cannot long endure close confinement. Within a certain length of time, which varies with the temperature and quantity of air available, tubers confined in hermetically sealed jars become moist over a part or the whole of their surface. If the tubers are then exposed to the air the moist surface areas turn brown and the color of the flesh at the center changes from white to pink then to black, producing a condition known as blackheart.
With a volume of air equal to the volume of the tubers a confinement of ten or twelve days is sufficient to produce the symptoms described provided the temperature is around 70° F. At 50-60° F. about twenty days are required; and at 40° F. a still longer time — somewhere between twenty-three and forty days.
Tubers confined in sealed jars with less than about ten times their volume of air are unable to do more than barely start sprouts. For normal sprouting about nineteen volumes of air per volume of tubers are required. Blackheart may be expected to appear whenever the volume of air available to the tubers is less than that required for normal sprouting.
Tubers suffering from insufficient aeration thru deep piling behave, in a general way, like tubers in sealed jars. They sprout feebly or not at all, become moist on the surface, discolor externally upon exposure to the air and are often affected with blackheart internally. While the data obtained from the experiments are insufficient for the formulation of definite rules, it appears that six feet should be the maximum depth of piling when potatoes are to be stored for several months at temperatures below 45° F. At temperatures above 50° F. the depth limit should be three feet if the potatoes are to be stored longer than three or four weeks.
Insufficient aeration during storage does not cause spindling sprout. It may retard sprouting temporarily, but when, subsequently, the tubers are supplied with air they sprout normally if at all.
Blackheart sometimes occurs in potatoes stored out-of-doors in piles and is due, undoubtedly, to insufficient aeration. It may be produced, also, by exposure to a temperature of 100-113° F. for fourteen to eighteen hours and often results from the overheating of potatoes during shipment in stove-heated cars.
The facts brought out in this investigation emphasize the importance of providing ventilation for potatoes in storage.
Neck-rot disease of onions.— During the past four years an exhaustive study has been made of a destructive rot of onions occurring in storage houses. Of the several common names by which this disease is known, neck-rot appears to be the most appropriate. Affected bulbs bear irregular, black, compact masses of fungus material (sclerotia) and a growth of smoke gray mold. These sclerotia and the mold are two different forms of the causal fungus which, tho long known, appears to be an undescribed species. Accordingly, it has been described and named Botrytis allii.
It has been determined that infection of the tubers takes place in the field and that the source of infection may be either wind-borne spores or fungus in the soil. A few of the infected bulbs show the disease while still in the field; but in the great majority of cases the disease does not develop until after the bulbs have been placed in storage.
age. Also, flowers of onions grown for seed may become infected by the fungus and blast.
Factors favorable to infection and the occurrence of neck-rot are: (1) Immaturity and imperfect curing of the bulbs; (2) the application of commercial fertilizers late in the season or in incorrect proportions; (3) the application of large quantities of stable manure before planting; (4) poor air drainage on the fields; (5) high humidity, high temperature and poor ventilation in the storage house.
Methods of control appear to lie mainly along the line of field sanitation, care of the curing crop and storage in houses which are properly constructed and regulated. Diseased bulbs should not be used as "mother bulbs" for producing the seed crop, since they are an important source of infection to the seed heads and, later, to growing crop onions in nearby fields. Refuse onions should not be piled near onion fields or used for fertilizer thereon. Care should be taken to avoid unnecessary bruising, on the topping machine and while handling, of stock to be stored. The crop should mature and die early. All refuse tops, soil and screenings should be removed. The bulbs should be thoroly cured in the field or drying sheds and stored in slatted crates in well constructed houses having ample facilities for ventilation' and the maintenance of low temperature.
Fumigation of the stock with formaldehyde gas either before or during storage has proven ineffective. While spraying the growing crop with bordeaux mixture has given some promising results it has not been tested sufficiently to warrant definite recommendations. Apparently, spraying is unpopular with onion growers because of certain difficulties encountered. Bulletin No. 437 gives a detailed account of these onion neck-rot studies.
Plant lice injurious to apple orchards.- Bulletin No. 431 is the second report of life-history studies and experiments with the apple aphides (Aphis sorbi, avena and pomi), which have for their object the establishment of efficient spraying practices for the protection of bearing apple orchards. In experiments with the insects all species attacked succulent tissues, as blossom and fruit stems, tender leaves and young apples. As a result of their activities various distortions of apples developed which were, as a rule, much more conspicuous with the fruits attacked by the rosy aphis (A. sorbi). In an experiment on the Station grounds, that is discussed with considerable detail, an application of lime-sulphur and nicotine solution at recommended strengths afforded efficient protection from the oat aphis and the rosy aphis. Of twelve auxiliary experiments, nine gave appreciable benefits from spraying. As losses by aphides vary according to locality and season, growers who are not certain as to the necessity of systematic spraying are advised to conduct a test for a period of years, for which brief directions are given.
The radish maggot.-- In Bulletin No. 442 attention is directed to the injurious work of the maggot (Phorbia brassice Bouché) on radishes and to experiments with screening as a means of protecting radish beds. Radishes produced in the spring months in this latitude are subject to attack by one brood of maggots which, in normal seasons, injure roots during the latter part of May or early June. As this vegetable is grown in most home gardens these dates closely coincide with the period when radishes are making their most succulent root growth. The results of experiments over a period of four years have shown plainly that a practical means of avoiding losses is to practice early sowing. During some seasons little leeway may be given as to choice of time for planting because of weather and soil conditions; however, it should be the rule to plant seed as soon as the physical condition of the soil permits. For the protection of radishes that are to be harvested during the period of the prevalence of the insects, growing of plants in frames covered with cheesecloth of 20 or 30 mesh has given excellent results. The roots grown by this method have in most seasons given larger yields and have been more succulent and tender than those produced in
The cherry leaf-beetle (Galerucella cavicollis Le Conte) is the subject of Bulletin No. 444. This is a study of the life history, habits and control of a native species which normally feeds on the bird cherry (Prunus pennsylvanica). Both insect and plant have the same geographical distribution. The history of the beetle records intermittent attacks on cultivated cherries. The most extensive outbreak of the insect occurred in 1915, and in New York was most serious in the territory west of Cayuga Lake and principally in the Lake Erie Valley, where considerable damage was done in orchards of cultivated cherries.
Seasonal conditions largely govern the life cycle of the insect, especially the development of the pupal stage. Oviposition begins in June and hatching of the eggs occurs during the latter part of July. After hatching the larvæ feed on the foliage, preferably of bird cherry. When compelled to feed on other trees they invariably succumb. Upon completing their growth the larvæ burrow into leaf mold or a short distance into the soil and form cells in which to pupate. The adults begin to emerge during the latter part of August.
Artificial control is affected by arsenicals used in combination with bordeaux mixture and nicotine sulphate, for the use of which directions are given.