EXPERIMENT STATION BULLETINS. 



381 



of the host plant merely sending short suckers (haustorla) into the epidermal 

 cells. It may attack any of the new growth but is most noticeable on the upper 

 surface of the leaves which appear covered with a white moldy growth pos- 

 sessing a powdery appearance. This is due to the great number of spores 

 (conidia) which are produced from, upright branches of the mycelium. These 

 are shed in abundance during summer thus serving to spread the disease during 

 the growing period. Later the affected parts show, under a hand lens, minute 

 black bodies scattered about, where the mycelium was most abundant. These are 

 the winter spore-cases (perithecia). In spring they burst open thus allowing 

 the escape of the enclosed spore sacks (asci). 



Treatment. Where treatment for no other fungous diseases is required sulphur 

 in the powdered form is usually used. This may be dusted on the vines when 

 dew is on. A solution of sulphide of potassium, one ounce to two gallons of 

 water, may also be used as a spray. The ammoniacal copper solution is also 

 recommended where the disease is of yearly occurrence. 



o^(y 



Fig. 31. — Microscopic structure of the powdery mildew fungus. A, li winter or resting spore 

 case (perithecium), bursting open to discliarge the contained spore sacs, (asci); b, a spore sac 

 (ascus), showing contained spores; c, mycelium from surface of leaf, giving rise to spore stalks 

 (conidiaphores), which break up into spores, thus producing the powdery appearance of 

 affected parts; d, one of the spore stalks, hisjhly magnified, showing how the spores (conidia), 

 are formed; e, mature summer, spore (conidium). (Original.) 



ANTIIKACXOSE, BIRDS EYE EOT. 



(Sphaceloma ampelinum De By.) 



The disease known by the above names does not seem to have proven as 

 serious a trouble to the grape growers of Michigan as of some other states. How- 

 ever, it has been noted from various localities and should be watched for each 

 season by those who grow this fruit to any considerable extent. It affects all 

 the young growing parts of the vines but is apt to be more noticeable when seen 

 on the fruit. The affected berries show, at first, brown spots which are sur- 

 rounded by a clearly defined margin. The center of the spots later becomes 

 whitish in color while the slightly raised margin assumes a deep brown or 

 purplish hue. Sometimes there is an inner circle of red color which helps to 

 accentuate the light center of the spots and gives to them the appearance sug- 

 gestive of a bird's eye. If several spots appear on a berry it soon shrivels up, 

 sometimes, however, only one side may be affected while the other develops thus 



