THE MONTHLY BULLETIN. 385 



EXPERIMENTAL WORK WITH BOTRYTIS CINEREA ON 

 GRAPES IN SAN JOAQUIN COUNTY. 



_ By William Garden, County Horticultural Commissioner, Stockton, Cal. 



Considerable damage has been done this year to grapes in San 

 Joaquin County by the fungus, Botrytis cinerea, kindly identified by 

 Professor H. S. Faweett, of the State University. This disease is not 

 altogether new in this portion of the State, but in previous years the 

 damage has been rather light. Experimental work was carried on with 

 both Bordeaux mixture and atomic sulphur. Plots growing both wine 

 and table grapes in widely separated parts of the county were used in 

 this experiment. 



PLOT No. 1. 



This plot is located at Weston, in the southern part of the county, 

 and contains 80 acres of land. It is 9 years old, and consists almost 

 entirely of Carignans, and has never produced over 40 per cent of a 

 crop. When the young shoots were about two inches long part of the 

 acreage was sprayed with Bordeaux mixture, the rest being treated 

 with atomic sulphur. Previous to blossoming the application Avas re- 

 peated. Conditions at this time looked very favorable for a heavy 

 crop. A vineyard not far distant from this plot was left unsprayed, 

 and much damage has been done to the crop at this time. Previous to 

 this it had been a cpiestion whether the failure of the newly formed 

 grapes was caused by a fungus, or was due to soil conditions. The 

 results of spraying with the aforementioned sprays indicate that the 

 Botrytis is responsible for the damage done. 



OTHER EXPERIMENTS. 



Other vineyards in the northern part of the county, growing on soil 

 almost identical with the plot treated in Experiment No. 1, were 

 .sprayed with atomic sulphur, and results have been very satisfactory. 

 One vineyard of 180 acres was sprayed three times — first in the dor- 

 mant season with lime sulphur, then with the regular Bordeaux mixture 

 aftertheshoots had started, and later with atomic sulphur. Indications 

 in this vineyard at the present time point towards a clean, heavy crop. 



