BLIGHTS OF CONIFEROUS NURSERY STOCK. 5 
mixture, ammoniacal copper carbonate, and copper acetate were 
tested repeatedly during several seasons. Unfortunately for the 
experiments, little trouble with the disease occurred at the times 
when the fungicides were used. In four cases, however, the disease 
attacked parts of the nursery containing experimental plats which 
had been more or less recently sprayed with copper mixtures con- 
taining soap. Im these cases there was no evidence that the fungi- 
cides afforded any protection. This lessens the likelihood that needle 
parasites are concerned in causing the disease. 
(2) On sandy soil the attacks which most closely imitate parasitic 
injury by killing definite patches occur suddenly and often simul- 
taneously in many parts of the nursery. Serious damage may appear 
through thousands of square feet of seed beds inside of 48 hours 
from the tire the first evidence occurs. This renders it unlikely 
that root parasites play any important part in causing the disease. 
(3) The most typical attacks of the disease observed at Halsey 
occurred on days when wind and temperature were high and humidity 
low and following nights which had been unusually warm and with- 
out dew—conditions which favor excessive transpiration. This em- 
phasizes the relation of transpiration to the disease. 
(4) In general, the most trouble occurs during dry seasons. The 
larger commercial nurseries in Minnesota and Iowa report that the 
most serious trouble they have had was during the very unusually 
dry summer of 1910. 
(5) Partial shade greatly decreases loss and entirely prevents 
trouble except in very severe attacks or during persistent drought. 
Shade was tested in five different attacks at Halsey in 1908, 1909, and 
1910, and in all cases controlled or greatly lessened the losses, as 
indicated by the results in adjacent shaded and unshaded plats. 
(6) Crowding strongly predisposes to the trouble. In the beds at 
Halsey the seedlings at the margins which have sent their roots out 
into the unoccupied paths are practically never attacked, though in 
some cases the entire interiors of beds have been killed. This im- 
munity of the edges of the beds is more marked on sandy soils than 
on heavier ones. 
(7) Attacks of the disease regularly occur when the soil is very 
dry. Very sandy soils, which are more quickly reduced to a low 
water content, are the commonest locations for the disease. In two 
different attacks at Halsey direct comparisons were made of soil 
moisture in diseased and relatively healthy areas, taking samples 
between the depths of 7 and 11 inches, where the greatest mass of 
absorbing roots lay. In one case the samples from the four points 
tested in the healthy area showed an average water content 32 per 
cent higher than that of the two points taken in the blighted stand 
adjacent. At the time of the other attack four samples were taken 
