MAINE AGRICUr.TURAl, KXPERIMI^NT STATION. 297 



not appeared, if possible, should be used. Some varieties are 

 moi-e resistant to the disease than others. Varying results 

 have been obtained from spraying with bordeaux mixture but 

 this is advised as a precautionary measure. 



Onion mildew is an important and destructive disease of 

 onions. It is mentioned here particularly because a case re- 

 ported from Hallowell in the summer of 1912 was the first 

 record of its occurrence in Maine since the department of plant 

 pathology was established at the Station. It appears in late 

 June or July. The fungus which causes it belongs to the same 

 general class as that to which the fungus causing the late 

 blight of the potato belongs. The disease is characterized by a 

 sudden wilting and death of the foliage and rapid spread of 

 the malady where large fields of onions are being grown. In 

 the early stages the attacked portions of the leaves have a furry 

 appearance with a slight violet tinge. Later these become' 

 mouldy, pale, streaked or blotched, collapsed and broken. 



For treatment, spraying with bordeaux mixture, particularly 

 a modified form having an addition of a sticky substance com- 

 posed of fish oil, resin and potash, has been fouuvl to be very 

 efiFective. 



With regards potato diseases, particularly late blight, the 

 season of 1912 gave very unexpected results. From past ex- 

 perience any prolonged period of rainy weather after the plants 

 have reached the blossoming stage is, in this State, practically 

 certain to result in widespread and destructive epidemics of late 

 blight on all but the most thoroughly sprayed potato fields. The 

 summer of 1912 was probably the first exception to this rule 

 that New England has experienced in many years. While the 

 potato growing season was abnormally wet and late blight of 

 the foliage and the associated decay of the tubers appeared, no 

 real severe cases of this disease were reported to the Station or 

 observed by the pathologists. 



There is one possible explanation for this failure of the 

 disease to appear in epidemic form. The fungus is carried 

 over winter in the seed tubers and spreads from these to the 

 j^oung plants in the spring. At this time of the year it is pro- 

 pagated very slowly, does no apparent damage, and consequently 

 is never seen by the average observer. In this region it never 

 breaks out in epidemic form till after the plants attain consid- 



