190 



FUNGOUS DISEASES OF PLANTS 



when either flowers or fruit produced on the twigs have already 

 fallen prey to the disease. In other words, the fungus must grow 

 directly from the fruit or blossom into the young twigs, since it 

 cannot readily penetrate the epidermis of the latter. Inoculation 



of the fungus into cuts on the 

 bark will, however, also result in 

 a twig infection. The effect of 

 the fungus upon the twig is to 

 produce a blight, the twig being 

 completely killed as the disease 

 progresses (Fig. 70). Peaches 

 and apricots are more subject to 

 the twig blight than other stone 

 fruits. 



Mummied fruits. The fruit 

 which has decayed may fall to 

 the ground or hang upon the 

 trees, gradually shrinking with 

 evaporation each to a crumpled, 

 dried mass, generally known as 

 a mummy. These mummied 

 fruits are the chief source of 

 infection the following season 

 under ordinary conditions. It 

 has been determined that the 

 spores produced one summer 

 may, under certain conditions 

 at least, live over until the fol- 

 lowing spring. Further, the 

 mycelium within the mummied 

 fruits more readily lives until 

 conditions favorable for growth 

 the following season. It is also possible that the spores which 

 have been blown about and adhere to bud scales, etc., may likewise 

 cause infection the following year. 



Rot in market fruit. Not only is this fungus a cause of consid- 

 erable loss in the orchard, but it also affects the fruit in shipment 

 or on the market. When the spores are abundant in the orchard, 



FIG. 70. APRICOT TWIG KILLED BY 

 THE BROWN ROT FUNGUS 



