70 Report of the Botanist of the 



A field of late cucumbers containing one and three-fourths acres 

 was divided into five plats, three of which were sprayed and the 

 other two unsprayed, the sprayed plats alternating with the un- 

 sprayed. Spraying was commenced when the plants were quite 

 small and repeated at intervals of from six to eleven days until 

 frost. In all, seven applications were made. 



The plants on the unsprayed plats were so violently attacked by 

 downy mildew that they ceased to produce any merchantable fruit 

 after August 21. The sprayed plants produced, after this date, 

 cucumbers which were sold for $260, which is at the rate of $173 

 per acre. There was, however, toward the close of the season, 

 considerable disease on the sprayed plats, enough to materially re- 

 duce the yield. This was due to the proximity of the diseased 

 plants on the unsprayed plats. It was believed that if no un- 

 sprayed plants had been left to furnish a breeding place for the 

 fungus the sprayed plants might have been kept practically free 

 from disease up to the close of the season. 



In 1897. — In order to determine what may be accomplished 

 when no unsprayed plants are left, another spraying experiment 4 

 on late cucumbers was made in 1897. 



An exact acre of late cucumbers was sprayed eight times. 

 There were no unsprayed plants in the immediate vicinity, the 

 nearest source of infection being an unsprayed muskmelon patch 

 about thirty rods distant. When frost came the plants were en- 

 tirely free from downy mildew and anthracnose, although both 

 of these diseases were abundant in most of the cucumber fields 

 in the vicinity. The acre yielded 101,960 merchantable cucum- 

 bers while the average yield of unsprayed fields was probably less 

 than 20,000 per acre. 



A second experiment 6 was made in 1897. Two hundred hills 

 were planted in May. One-half of these were thoroughly sprayed 

 throughout the season — in all, fourteen times. The other half 

 were not sprayed. 



* Reported in Bui. 138: 641-fW3. 

 Reported in Bui. 138: 636-639. 



