120 TWENTY-FIFTH ANNIVERSARY REPORT. 
twigs to die suddenly in midsummer. Although fire blight is quite 
common and sometimes a destructive disease of apples in New 
York, pear trees suffer-most from it. Consequently, in the inves- 
tigation of fire blight attention was centered on the pear, and the 
apple given only secondary consideration. Practically all that was 
done with the apple was the making of cross-inoculation experi- 
ments? to determine whether the organism causing fire blight of 
apple was the same as that causing fire blight of pear. Twigs and 
fruit of apple were artificially inoculated with pure cultures of 
bacteria obtained from blighted pear twigs. Likewise, twigs and 
fruit of pear were inoculated with bacteria from blighted apple 
twigs. In both cases fire blight was successfully reproduced, show- 
ing that the disease is the same on the two hosts. The fire blight 
investigations will be discussed more fully under pear diseases on 
page 142. 
Scab,? the most important apple disease, has been given attention 
commensurate with its importance. Almost all of the work done by 
the Station on this disease has been in the nature of experiments in 
its control. Twenty-five years ago almost nothing was known con- 
cerning the control of apple scab. In 1883 Prof. Burrill,* a noted 
authority on plant diseases, still living, recommended spraying the © 
trees with kerosene emulsion! Chiefly through experiments made 
by various experiment stations, led by the Ohio Station,® we have 
to-day a treatment for scab which, although not entirely satisfactory, 
is yet thoroughly practicable and profitable; namely, spraying with 
bordeaux mixture. The earliest experiments of this Station were 
with hyposulphite of soda as a spray. This reduced the amount of 
scab somewhat without injury to the foliage. Another fungicide,’ 
a mixture of copper sulphate, ammonia and water, ruined the fol- 
iage. Then potassium sulphide and calcium sulphide were tested.§ 
The former proved of some value, but calcium sulphide was a 
complete failure. The first experiments with bordeaux mixture on 
apples at the Station were made in 1894. In the report of these 
experiments? it was recommended that three sprayings be made as 
* Rpt. 3:359 (1884). 
* Venturia inequalis (Cke.) Aderh. 
* Burrill, T. J. Trans. Mississippi Valley Hort. Soc. 1:206 (1883). 
*Green, W. J. Ohio Sta. Bul. Vol. IV, No. 9, pp. 193-212 (1891). 
* Rpts. 4:260 (1895); 5:173 (1896) ; 6:99 (1807) . 
*Rpt.6s101 (1887). 
* Rpt. 7:154-157 (1888). 
* Bul. 84:19, 29-33 (1895); same in Rpt. 13:663, 673-678. 
