4 MISC. PUBLICATION 3 4 0, U. S. DEPT. OF AGRICULTURE 



Recommended methods of control 3 include the use of commercial 

 lime-sulphur as a dormant spray and of bordeaux mixture during the 

 growing season. The removal of all diseased branches or shoots dur- 

 ing the winter is also desirable (17, 18, 26, 28). 



BLACK MEASLES 



The disease known as black measles is characterized by numerous 

 small, irregularly shaped spots, varying in color from bluish or purplish 

 to black and scattered over any or all of the surface of the berry 

 (pi. 2, B). It is apparently nonparasitic in origin; it may occur, how- 

 ever, on fruit from vines that show no evidence of the disease on the 

 foliage. The name "black mildew," sometimes applied to it, is mis- 

 leading and should not be used. True mildew russetting, caused by 

 one of the fungi known as powdery mildew, is delicate, lacy, light 

 brown, and never bluish or black. 



Black measles sometimes appears in high percentage in the vine- 

 yard, but is usually culled out carefully at the packing house so that 

 it rarely appears on the market. The varieties most commonly affected 

 are Malaga, Emperor, Alexandria (Muscat), Burger, Carignane, and 

 Alicante Bouschet; others of less importance commercially also show 

 the spotting at times. The disease does not develop or spread in 

 storage or transit. 



Spraying or swabbing the pruning wounds with sodium arsenite 

 solution while the vines are dormant, 3 or 4 weeks after pruning, has 

 given control in some vineyards. Care must be taken to apply the 

 solution before the buds begin to swell, and to avoid strong solutions 

 since some vineyards have been injured by this treatment (4, 6). 



BLACK MOLD ROT 



(Aspergillus niger Van Tiegh.) 



OCCURRENCE, SYMPTOMS, AND EFFECTS 



Black mold rot has been reported only on vinifera grapes from 

 California. The rot is most often seen during the hot summer months 

 and on varieties that mature during this season. All commercial 

 varieties may be affected^ but those that suffer most are Zinfandel, 

 Alicante Bouschet, Sultanina (Thompson Seedless), Malaga, Castiza, 

 (Red Malaga) , and Burger. All of these frequently form bunches so 

 tight that berries are broken merely by their pressure against one 

 another in the bunch. The consequent leakage of juice furnishes a 

 culture medium for the germination of spores of black mold and of 

 other fungi, and for the growth of the mycelium they produce. Hence, 

 to account for the occurrence of the rot on these varieties in the vine- 

 yard it is not necessary to assume anything more than the presence of 

 spores of the fungus in the air. Varieties that form loose, open 

 bunches, such as Emperor and Alexandria (Muscat), are rarely 

 attacked by black mold except during or soon after periods of rainy 

 weather. In table varieties, the loss on the vine of grapes that are 

 unfit for packing may range from less than 1 percent to as much as 

 15 or 20 percent. 



3 Porter, B. A., and Demaree, J. B. the control of grape insects and diseases. U. S. Dept. 

 Agr. Cir., 8 pp. 1936. [Mimeographed.] 



