258 



FUNGOUS DISEASES OF PLANTS 



upon these are borne minute, cylindrical, or slightly curved 

 conidia. It is, however, doubtful if this last mentioned pycnidial 

 form is either common or of much consequence in the rapid 

 distribution of the fungus. 



The ascigerous stage was first found and named in 1880, and 

 since that time the name has been more frequently changed than 

 has the fungus been accurately studied. It is stated that the asci 

 were first found upon berries which had hung upon the vines 

 during the winter and had subsequently been dropped into water 

 for a few days. Since that time the perfect stage (Fig. 112, b) has 



been frequently detected on af- 

 fected berries which have lain 

 under favorable conditions dur- 

 ing the spring months, as when 

 covered by leaves and grass. It 

 would seem, however, that very 

 few observations have been 

 systematically made to deter- 

 mine the time of development 

 of the ascospores. The asci 

 may apparently develop in per- 

 ithecia which have previously 

 served as pycnidia, or resting 

 stromatic masses may give rise 

 to the perithecia directly. The 

 asci are broadly clavate, some- 

 times slightly curved, and they 

 contain eight nonseptate, hyaline spores, the latter measuring 1 2- 

 17 x 4. 5-5 /^. They are generally ovate. 



Control. The most efficient remedy for the black rot is 

 Bordeaux mixture. After cleaning the vineyard as well as possi- 

 ble of the pruned and diseased litter, the old berries being 

 covered by early plowing, Bordeaux should be thoroughly applied, 

 covering vines, posts, and trellis just as the buds are swelling in 

 the early spring. A second application is made as the buds 

 unfold, and subsequently the vines should be sprayed about every 

 two weeks, until five or six applications have been made. The 

 nature of the season, however, will determine how late it will be 



FlG. 112. GuiGNARDIA BlDWELLII: SEC- 

 TIONS OF PHOMA AND ASCIGEROUS 

 STAGES 



