April, ’24] 
DAVIS: SAN JOSE SCALE ESTIMATES 
193 
ly recognize the loss of an animal or the destruction of a clover crop by 
grasshoppers, or an onion crop by thrips but he is less likely to recognize 
gradual injury to orchard trees or realize the relative importance of the 
loss of trees which required careful attention for 15 or 20 years. 
We find, on analyzing the problem, that the San Jose scale is an im¬ 
portant factor in profitable orcharding from several angles. 
First, the moderate infestation may weaken the trees. 
Second, the moderate infestation, if not checked, soon becomes a 
serious one, resulting in the killing of individual branches and usually 
the entire tree. 
Third, the moderate or severe infestation may be completely eradi¬ 
cated and still there remains an after-effect which may last for a number 
of years, preventing the maturing of a satisfactory or profitable crop. 
Fourth, the light, moderate, or severe infestation may cause a 
spotting of the fruit, resulting in a depreciation in value, often reducing 
the crop below the point of profit. 
Fifth, trees weakened by the San Jose Scale are subject to many 
additional troubles. For example, on apple, bitter rot often follows 
scale infestation in southern Indiana and farther south; on peach, the 
shot hole borer has an excellent opportunity to gain a foothold, in fact, it 
may infest and kill the trees in a single season. 
Other factors must be kept in mind. Thus we find the more vigorous 
trees are more subject to injury, probably because scale increases more 
rapidly. Likewise certain varieties are more subject to heavy infesta¬ 
tion than others, thus, in Indiana, vigorous Grimes trees have been 
killed in one year, when the dormant spray was omitted. Similarly, 
the length of time that encrusted trees will recover after being cleaned up 
depends on varieties. 
To determine the monetary losses from different degrees and kinds of 
infestation, a questionnaire was sent to 25 orchardists in Indiana, and 
of the 18 replies received, the following averages were figured. 
The average yield of a twenty-year old apple tree is 12 bushels and the 
average value of the tree is $40.00. The depreciation in value of the 
crop, as a result of scale spotting varies from 15 to 100 per cent, averag¬ 
ing 50 per cent. A tree weakened sufficiently to make production 
unprofitable requires two to five years to bring it back into profitable 
bearing, after the scale has been controlled, Figures submitted by 
orchardists show the cost of one dormant spray to be 15 to 00 cents per 
tree, the lowest estimate for lubricating oil emulsion, the intermediate 
costs for lime-sulphur, and the highest expense for the more expensive 
