"24 CRANBERRY DISEASES. 



Fresh pycnospores have been placed in drops of water upon fruit 

 kept in sterile moist chambers, but Avithout any noticeable result. 

 The spores germinate, but are apparently unable to penetrate the 

 epidermis of the fruit. That infection of the foliage and fruit in- 

 stead of taking place in whole or in part by way of the roots and up 

 through the stems, as supposed by Doctor Halsted, arises from exter- 

 nal sources seems to be proved by the very satisfactory results of 

 spraying experiments and by. the observations already recorded. Sev- 

 eral tips of vines bearing leaves, collected September 15, which had 

 been thoroughly sprayed during the season, Avere carefully Avashed 

 Avitli corrosiA^e sublimate and placed in sterile moist chambers. A 

 feAv fungi developed in a very fcAV of these leaves. Other leaves, 

 collected at the same time from adjacent vines Avhich had not been 

 sprayed, Avere treated in the same manner. These Avere found to be 

 completely infested Avith fungi, and the pycnidia of Guignardia de- 

 veloped in abundance on almost every leaf. 



A considerable quantity of fruit which had been sprayed was 

 treated in the same manner as the leaves already mentioned. As a 

 result, 1,200 sprayed berries picked on September 18 shoAved on 

 October 18 but 9.8 per cent of diseased fruit, Avhile the same number 

 of unsprayed berries from the same source kept under the same con- 

 ditions in the laboratory for the same period shoAved 38.1 per cent 

 of diseased fruit. The only explanation of these results in the light 

 of our present knoAvledge of the effect of Bordeaux mixture is that 

 most of the spores of the fungus had been destroyed by the spraying 

 and therefore did not gain entrance to the leaves and fruit. 



TREATMENT. 



Applications to the soil.— Xci'mg upon the supposition that the 

 cranberry scald Avas primarily due to unfavorable soil conditions or 

 to fungi attacking the plant by Avay of the root system, chemicals 

 or fungicides to be applied to the soil were suggested as a remedy 

 by Doctor Taylor,'* and later they Avere tried by Doctor Halsted." 

 Lime, plaster, salt, sulphur, copper sulphate, and iron sulphate were 

 tried in diiferent quantities. No decided benefit is reported to have 

 resulted from these applications. 



Improving the condition of the plants. — It is a matter of general 

 observation that the cranberry scald is much more serious on certain 

 bogs or portions of bogs than on others. The conditions obtaining in 

 the soil and Avater of these diseased areas no doubt have much to do 

 with the prevalence of the disease. The factors concerned are so 

 complex, however, that it is difficult to demonstrate satisfactorily 

 exactly Avhat they are and Avhich are of greatest importance. The 

 experience of various groAvers appears to shoAv that the control of the 



110 



