— 37 — 



(2) Spraying with Bordeaux mixture is a very effective remedy. Experiments 

 at the VermonL Station sliow that it pays to spray with Bordeaux even if the 

 blight is not present. 



(3) Keeping the storage house dry and cool. 



(4) If the tops of the potatoes are infected, they should not be harvested 

 until they have died down, unless the attack is particularly severe and the soil 

 wet and heavy. Tubers harvested while the spores are abundant on the foliage 

 are very likely to develop rot in storage. 



THE DOWNY MILDEW OF THE GRAPE. 



Symptoms. — The fungus may attack all the young portions. On the infected 

 leaf, yellowish spots appear which are rather indefinite and irregular in outline and 



Downy Mildew of Grape (Plastnopara viticola). A. portion of the mycelium from a diseased grape'. 

 B. A tuft of spore stalks ; C. Mature Spores : D. thick walled resting spore (from Longyear) . 



are more evident on the under surface. Shortly after the spots appear the coni- 

 diophores are given off through the stomata of the under side. When conditions 

 are favourable for the development of the fungus, the leaves may be killed and 

 will shrivel up and fall off. When the young fruit is attacked there is considerable 

 loss. 



Morphology. — The mycelium is of the typical form described for the fam- 

 ily. It grows abundantly in the intercellular spaces. The haustoria are button 

 shaped. Several conidiophores emerge from a single stoma and each becomes 

 constricted in passing through the pore. Outside the stoma they again attain 



