50 
THE NATIONAL NURSERYMAN 
CONTROL OF “DAMPING OFF.” 
Damping-off Disease of Young Coniferous Seedlings 
Effectively Controlled by Soil Disinfectants. 
Damping-off of coniferous seedlings has been one of 
the worst enemies of nurserymen. This is caused by sev¬ 
eral parasite fungi which attack and rot the stem and 
root of young seedlings. The loss from this source is not 
generally appreciated, for the poor stand of seedlings is 
frequently laid to poor germination. While the loss in 
one year from this cause may amount to but 10 per cent., 
yet in the next year damping-off may cause a total fail¬ 
ure of the stand. This uncertainty of crop has resulted 
in the high cost of coniferous trees for forest planting 
and has in the past caused American nurserymen to pur- 
shase their seedling stock in Europe. On account of the 
white pine blister rust, and the pine shoot moth introduc¬ 
ed on imported pines from Europe, an embargo has been 
placed on all pine nursery stock grown in Europe. This 
makes it doubly important that the damping-off of seed¬ 
lings be controlled. 
A measure of control has been secured at some nur¬ 
series by the use of sterile subsoil in small scale experi¬ 
ments. but this is not altogether practicable when consid¬ 
ered on a large scale. Excessive moisture and shade in 
the seed bed should be avoided. Seeds should not be 
sown any thicker than necessary to secure a good stand, 
for a crowded stand makes it easier for the damping-off 
fungi to spread from one plant to another. Sowing in 
summer or late fall has resulted in decreased losses at 
some nurseries and is worthy of trial. 
Soil disinfection, however, has proved the best method 
of combating the disease. Sulphuric acid, copper sul¬ 
phate. zinc chloride and formaldehyde have given better 
results than a large number of other chemicals used, in 
experiments carried on in twenty-one different localities. 
It is only possible to learn by trial just which chemical 
agent will best control damping-off in any given locality 
or on a given soil. At most nurseries sulfuric acid has 
given the best results. Treatment with this acid not only 
reduces loss from damping-off. but increases germina¬ 
tion. The number of seedlings secured in the treated 
beds has ranged from one and one-quarter to ten or even 
twenty times that secured in adjoining untreated beds. 
One of the most desirable features of the acid treatment 
is the reduction in the number of weeds. The saving in 
the cost of weeding has at one Nebraska nursery more 
than paid for the cost of the acid treatment. The reduc¬ 
tion in the weeds and the stimulation given by the acid 
treatment has at a Kansas nursery resulted in jack pine 
seedlings three times the height of seedlings grown in 
untreated beds. 
Sulfuric acid is applied to the seed beds in a solution of 
water just after the seed is sown and covered. From Vs 
to % fluid ounce of acid per square foot is dissolved in 
from \y 2 to 2 pints of water, and applied with a paraffin- 
coated sprinkler. Care is necessary in the use of the so¬ 
lution to keep it from the clothes and shoes, because of 
its corrosive action. Chemical injury may result in some 
cases to the roots, and it then becomes necessary to 
sprinkle the beds during germination once or twice daily. 
When the seedlings have their roots down three-quarters 
of an inch, there is little danger from chemical injury. 
The Department of Agriculture has a special bulletin 
dealing with “Injury by Disinfectants to Seeds and Roots 
in Sandy Soils.” Individual conditions at each nursery 
must decide how much acid is necessary and whether 
special watering is needed to prevent acid injury to the 
roots. 
Where there is considerable quantity of carbonates in 
the soil, their presence being indicated by an efferves¬ 
cence when a strong acid solution is applied, acid is not 
likely to be effective as a disinfectant. Copper sulphate 
and zinc chloride have been found good substitutes. The 
range of use of these chemicals which have proved suc¬ 
cessful in controlling damping-off is for copper sulphate 
Vs to 5-16 ounce per square foot, and for zinc chloride 
Vi to % ounce per square foot. These should be dissolv¬ 
ed in water as for the acid treatment. Roth the copper 
and zinc salts have at times been found injuring the roots 
of seedlings. Special watering will prevent the injury. 
Formaldehyde has been found injurious to seeds and 
must therefore be applied before seed sowing. At a Min¬ 
nesota nursery best results were secured by applying 9 
days before sowing a formaldehyde solution of from V 2 
to % ounce per square foot, in from IV2 to 2 pints of 
water. It is necessary to cover the seed bed immediately 
after applying the solution in order to secure thorough 
penetration, and to prevent the too rapid evaporation of 
the gas. 
Heat sterilization of the seed bed has been of value at 
some nurseries, though this method of treatment is more 
expensive than the acid teatinent. Of all the treatments 
acid should be given the first trial, since it has proved 
moie successful on more soils than any of the other chem¬ 
icals used. 
If any nurservmen contemplate the use of soil disin¬ 
fectants they should write to the Department of Agricul¬ 
ture, for specific advice adapted to their particular loca¬ 
tion. and keep the department informed of their experi¬ 
ence. 
Notice of Proposed Quarantine on Account of the 
White Pine Blister Rust (Peridermium strobi Kleb.). 
Notice is hereby given that the Secretary of Agricul¬ 
ture has determined that there exists in Europe. Asia, the 
Dominion of Canada and Newfoundland a dangerous 
pine disease known as the white pine blister rust (Peri¬ 
dermium strobi Kleb.). new to and not heretofore widely 
prevalent or distributed within or throughout the United 
States, and that it may be necessary to forbid the impor¬ 
tation into the United States of all species and varieties 
of the genera Pibes and Grossularia, known to be car¬ 
riers of this dangerous pine disease. 
In accordance with the provisions of Section 7 of the 
Plant Quarantine Act of August 20, 1912 (37 Stat. L.. 
315). a public hearing will be held at the Department of 
Agriculture, Washington, D. C., at ten o’clock A. M., on 
February 4. 1916. in order to determine whether or not 
importations of all or certain species and varieties of the 
