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Issued April 30, 1908.

ees DEPARTMENT. OF AGRICULTURE,

BUREAU OF PLANT INDUSTRY—Circular No. 4.
. B. T. GALLOWAY, Chief of Bureau.

THE TREATMENT OF DAMPING-OFF
IN CONIFEROUS SEEDLINGS.

BY

PERLEY SPAULDING,
SCIENTIFIC ASSISTANT, LABORATORY OF FoREsT PATHOLOGY.

38045— Cir. 4—08

BUREAU OF PLANT INDUSTRY.

Pathologist and Physiologist, and Chief of Bureau, Beverly T. Galloway.

Pathologist and Physiologist, and Assistant Chief of Bureau, Albert F. Woods.

Laboratory of Plant Pathology, Exwin WF. Smith, Pathologist in Charge.

Investigations of Diseases of I'ruits, Merton B. Waite, Pathologist in Charge.

Labeoratory of Forest Pathology, Haven Metcalf, Pathologist in Charge.

Truck Crop Diseases and Plant Disease Survey, William A. Orton, Pathologist in Charge.

Plant Life History Investigations, Walter T. Swingle, Physiologist in Charge.

Cotton Breeding Investigations, Archibald D. Shame] and Daniel N. Shoemaker, Physiolo-
gists in Charge. :

Tobacco Investigations, Archibald D. Shamel, Wightman W. Garner, and Ernest H.
Mathewson, in Charge.

Corn Investigations, Charles P,. Hartley, Physiologist in Charge.

Alkali and Drought Resistant Plant Breeding Investigations, Thomas H. Kearney, Physi-
ologist in Charge. 7

Soil Bacteriology and Water Purification Investigations, Karl F. Kellerman, Physiologist
in Charge.

Bionomic Investigations of Tropical and Subtropical Plants, Orator F. Cook, Bionomist
in Charge.

Drug and Poisonous Plant Investigations and Tea Culture Investigations, Rodney H.
True, Physiologist in Charge.

Physical Laboratory, Lyman J. Briggs, Physicist in Charge.

Crop Technology and Fiber Plant Investigations, Nathan A. Cobb, Crop Technologist in
Charge. : -

Taxonomic and Range Investigations, Frederick V. Coville, Botanist in Charge.

Farm Management Investigations, William J. Spillman, Agriculturist in Charge.

Grain Investigations, Mark Alfred Carleton, Cerealist in Charge.

Arlington Exrperimental Farm, Lee C. Corbett, Horticulturist in Charge.

Vegetable Testing Gardens, William W: Tracy, sr., Superintendent. |

Sugar-Bect Investigations, Charles O. Townsend, Pathologist in Charge.

Western Agricultural Extension Investigations, Carl S. Scofield, Agriculturist in Charge.

Dry-Land Agriculture Investigations, ©. Channing Chilcott, Agriculturist in Charge.

Pomological Collections, Gustavus B. Brackett, Pomologist in Charge.

Field Investigations in Pomology, William A. Taylor and G. Harold Powell, Pomologists
in Charge.

ALeperimental Gardens and Grounds, Edward M. Pyrnes, Superintendent.

Loreign Seed and Plant {ntroduction, David Fairchild, Agricultural Explorer in Charge.

Forage Crop Investigations, Charles V. Piper, Agrostologist in Charge.

Seed Laboratory, Edgar Brown, Botanist in,Charge.

Grain Standardization, John D. Shanahan, Crop Technologist in Charge.

Subtropical Laboratory and Garden, Miami, Fla., Ernst A. Bessey, Pathologist in Charge

Plant Introduction Garden, Chico, Cal., August Mayer, Expert in Charge.

South Teras Garden, Brownsville, Tex., Edward C. Green, Pomologist in Charge.

Farmers’ Cooperative Demonstration Wgrk, Seaman A. Knapp, Special Agent in Charge.

Seed Distribution> (Directed by Chief of Bureau), Lisle Morrison, Assistant in General
Charge. -

*

Editor, J. . Rockwell.
Chief Clerk, James H. Jones.

CON ALE NTS:

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B. P. I.— 364.

THE TREATMENT OF DAMPING-OFF IN
CONIFEROUS SEEDLINGS.

INTRODUCTION.

Experiments have been carried on by the writer for several years
in testing the effect of various chemicals upon the damping-off dis-
eases of tender coniferous seedlings. These troubles are great obsta-
cles to the successful production of such seedlings in large num-
bers for use in replanting waste or unoccupied land. They are
caused by a number of different fungi which are being studied and
will shortly be described.

The results of the first experiments, which were carried on entirely
in the greenhouse, were taken as indications of what might be
expected in actual nursery practice. It was felt, however, that the
work should be extended to field conditions, and upon testing the
preliminary results there it was found that they could be taken only
as very meager and insufficient indications of the results to be
obtained in the field.

During the season of 1907, field experiments. were conducted in
several nurseries of the New York Forest, Fish, and Game Commis-
sion (one of which is operated in cooperation with the Forest Service
of the United States Department of Agriculture) and of the Ver-
mont State Forestry Commission, located, respectively, at Saranac
Inn, N. Y., and Burlington, Vt. These experiments yielded very
interesting results, but because of their preliminary nature it is felt
that without further very rigid tests along similar lines they can not
be accepted as furnishing conclusive proof of the comparative value
of the chemicals used.

The great interest centering about these diseases, however, makes
of value every scrap of practical information concerning methods of
prevention. Until conclusive results are obtained the present ones
may therefore prove useful to nurserymen, but they should be
_ accepted with the distinct understanding that they are preliminary
and are subject to later modification.

6 TREATMENT OF DAMPING-OFF IN CONIFEROUS SEEDLINGS.

The tests here outlined are being continued on a more extensive
scale, and it is hoped that the present season’s work will give such
results that there can be no doubt as to the conclusions to be drawn
from them.

PROCEDURE IN EXPERIMENTS.

The plots used were located in seed beds 12 feet long and 4 feet
wide, each bed being divided into three equal parts 4 feet square.
The chemicals were used in fine powders or in solutions, according
to their original form and nature. The solutions were applied with
an ordinary sprinkling can, while the powders were sifted on the
beds with a very simple form of duster having a perforated bottom,
through which the powder was shaken. The solutions were applied
to the soil before the seeds were sown, and then again about five days
after the seedlings had come up. The powders were applied to the
beds only after the seedlings had been up for three or ,four days.
They were apphed in very hght coatings, which were renewed.
promptly after each rain. This renewal is not necessary except for
a period of about two weeks, beginning three or four days after ger-
mination, when the seedlings are most susceptible to the attacks of

the damping-off fungi.
POWDERS USED.

Sulphur.—Sulphur was obtained in three forms: Washed, resub-
limed, and precipitated. Favorable results were given by all, but
the first led the others slightly. It was noted, too, that a distinct
odor of sulphur could be detected at least 8 inches above the surface
of the plot treated with washed sulphur, while no perceptible odor
could be detected over the other two at a greater distance above the
surface than 1 or 2 inches. This difference was as marked several
days after the sulphur had been apphed as it was immediately after
the application was made.

Diy Bordeaux mixture.—Dry Bordeaux mixture made according
to Scott’s formula” was also tried, but the method of preparation
is too tedious and time consuming to be of use in the case of a disease
like damping-off unless the mixture is made up some time in advance.
It is seldom practicable fcr the nurseryman to give the necessary
time for its preparation, owing to the pressure of other duties at this
period of the year. This powder was accordingly discarded for a
copper sulphate and lime mixture which is easily and quickly made
up as required and apparently should give as good results as the Bor-
deaux preparation.

Copper sulphate and lime—Powdered sulphate of copper was
mixed with powdered lime, at the rate of 1 pound of the former to

2@Waite, M. B. Fungicides. U. S. Department of Agriculture, Farmers’ Bul-
letin 243, pp. 11-12, 1906. -

TREATMENT OF DAMPING-OFF IN CONIFEROUS SEEDLINGS. (i

10 pounds of the latter, in the following way: Fresh stone lime was
slaked with as little water as would keep the slaking in progress.
In this way slaked lime was obtained in the form of a fine powder.
This was screened and very thoroughly mixed with the powdered
copper sulphate, and was then ready to be used. Attention is called
to the need of thoroughly mixing the, two ingredients, as disastrous
results are likely to ensue if the copper sulphate is not properly
diluted with the lime.

This mixture was used very freely after the seedlings had come up.
Absolutely no injurious results could be noted, even when the applica-
tions were made early in the morning while the seedlings were still
wet with dew so that the powder stuck to them. It may be said that
the better time to apply the powders and also the solutions is late in
the afternoon. The powders will then adhere very shghtly to the
plantlets and practically all of the powder will fall on the soil, where
it is wanted. |

This copper and lime mixture was used upon the following species:
Pinus sylvestris, P. pondcrosa, P. strobus, P. resinosa, Picea rubens,
P. excelsa, and Pseudotsuga taxifolia. Very good results were ob-
tained in checking the damping-off with it, and it is believed to be
one of the mixtures tested which may prove of value commercially.

SGLUTIONS USED.

Potassium sulphid and permanganate.—A solution of potassium
sulphid, made at the rate of 1 ounce of dry chemical to 1 gallon of
water and applied to the soil before sowing the seed, gave no definite
results because of the absence of the disease in the experimental plots.
This was also true of a solution of potassium permanganate, mixed at
the rate of 1 gram of chemical to 1 gallon of water and similarly
applied.

Formalin——Commercial 40 per cent formalin, used at the rate of 4
ounces to 3 gallons of water, when applied to the soil before seeding
and not afterward repeated, seemed to have no effect whatever upon
the disease. The check plot, indeed, was much better, as were all of
the other plots, both treated and untreated, located in that section of
the nursery. When applied as stated and repeated after the seedlings
had come up, the results were poor. It is now believed that formalin
is of little value with the damping-off diseases of coniferous seedlings
unless supplemented after the germination of the seed with some other
efficient chemical. The results were disappointing when compared
with those obtained with some of the other chemicals.

Sulphuric acid.—The best results were obtained with weak solutions
of sulphuric acid. A solution mixed at the rate of 1 ounce of acid to
1 gallon of water was applied to the soil several days before sowing

8 TREATMENT OF: DAMPING-OFF IN CONIFEROUS SEEDLINGS.

the seed, until it was thoroughly drenched, and the treatment was re-
peated about a week after the seedlings came up. The treated plot
was in excellent condition in December; there was a very good stand
of fine, healthy seedlings and the soil was entirely free from alge and
moss. The check plot, on the other hand, had practically no seedlings
left, and the soil was green with alge and moss.

This solution of sulphuric acid was applied to young seedlings ofa
number of different species, and but one showed any ill effects. This
was Norway spruce (Picea excclsa). It is not advisable to use an
acid solution as strong as this upon the plants. Kraemer @ has shown
that a solution of sulphuric acid at the rate of 1 to 500 is as strong as
should generally be used upon plant tissues, and this is recommended
rather than the much stronger one used in these experiments. For
soil treatment the stronger solution will probably prove preferable.

Approved:
James WILSON,
Secretary of Agriculture.

WasuineTon, D. C., April 6, 1908.

@\raemer, Henry. Dilute Sulphuric Acid as a Fungicide. Proceedings,
American Philosophical Society, vol. 45, pp. 157-163, 1906.

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