EXPERIMENT STATION BULLETINS. 391 



This is the most common and important of the fungous diseases of the straw- 

 berry. It attacks the leaves causing at first purple spots which gradually be- 

 come lighter in the center until they finally stand out clearly against the green 

 background of the leaf as rounded, light colored spots surrounded with a brownish- 

 purple border. Although 'these spots are not large they often run together some- 

 times covering a large part of the leaf. During the summer the spots give rise 

 to minute tufts of spore-bearing stalks. The spores given off by these are capable 

 of spreading the fungous parasite during the growing season. 



Badly affected leaves die during summer and in their tissues minute, black 

 bodies (perithecia) develop during the latter part of autumn. These bodies, 

 which are the resting-spore cases, are situated just under the epidermis of the 

 dead leaves but possess a projecting mouth which opens outside the leaf. On 

 the interior of these spore cases may be seen with the microscope many very 

 small spore sacks (asci) each containing eight two-celled spores. These spores 

 are not mature until in spring, at which time they are capable of starting the 

 disease on the new foliage. 



Treatment should consist of spraying with some reliable fungicide, when the 

 new foliage is appearing in spring, with a second application when fruit is 

 setting, to be repeated after harvesting the fruit if the plantation is to be kept. 

 Mowing and burning the leaves after the fruit is gathered, has been found to 

 reduce this disease by destroying the old leaves in which the fungus hibernates. 



WOUND FUNGI. 



Among the numerous fungous inhabitants of the orchard are a number of so 

 called wound fungi. While ordinarily existing as saprophytes, living in the dead 

 tissues of the trees, these fungi may under favorable conditions assume the role 

 of true parasites and cause the death of living portions of their host. As the 

 name implies such fungi gain an entrance into the roots, trunk or limbs of a 

 tree by means of wounds. The wounds may be of various origin, such as those 

 caused by hail, "sun scald," splitting at the crotches from strong winds or 

 the weight of snow, ice, or heavy crops of fruit; injuries caused by animals pas- 

 tured in the orchard, and bruises made while plowing and cultivating among 

 the trees. Improper times and methods of pruning also make it possible in a 

 great many cases for the establishment of wound parasites. Fig. 41 shows the 

 trunk of a tree one side of which has become inhabited by a colony of several 

 kinds of these wound fungi. They first gained an entrance through extensive 

 ruptures of the bark due to sun scald. The spores of these fungi, falling into 

 the crevices thus formed, have found a favorable place to grow, and, while 

 at first the exuding sap and dead cells of the inner bark served to nourish the 

 young mycelium, the trunk is now being slowly invaded, the water circulation 

 impeded or cut off in some places, and the trunk weakened by the rotting of the 

 wood. "While such trees often live and bear fruit for a number of years they 

 gradually fall into a condition of unsightly decay and eventual death. Very 

 often the end of a large branch which has been left too long in pruning and 

 without a protective coating gives entrance to such fungi. In such cases the 

 trunk is frequently hollowed out in time by the decay of the heart wood with a 

 convenient opening left for the birds and squirrels. Such trees are apt to yield 

 to the force of storms especially when loaded with fruit. 



Most of the fungi which act as wound parasites belong to the pore-and-gill- 

 bearing fungi, many of which are of considerable size when in fruit. The fol- 

 lowing species have been noted by the writer as occurring on trunks and limbs 

 of fruit trees: — 



Polystictus versicolor. 

 Polyporus adustus. 

 Polyporus resinosus. 

 Fomes leucophaeus. 

 Fomes igniarius. 

 Irpex sinuosus. 

 Schizophyllum commune. 

 Collybia velutipes. 

 Pholiota adiposa. 

 Pleurotus ostreatus. 

 Pleurotus areolatus. 



