juneis. i9i6 BacteYial Wilt of Cucurbits 429 



the latter, showed a considerably greater evidence of resistance. For 

 these plants, therefore, this method of control is at least worthy of 

 further investigation, but up to the present time the observations and 

 experiments do not justify definite conclusions. 



SPRAYING 



In two fields situated near the variety-test block a series of spraying 

 experiments was carried out in 191 5 upon the Fordhook Famous cucum- 

 ber, planted on June 5 and 7, and Woodruffs Hybrid cucumber, planted on 

 June I. The relation between the striped cucumber beetle and wilt in 

 these two fields has already been detailed (p. 420 and fig. i). The relative 

 merits of Bordeaux mixture alone, Bordeaux mixture with lead arsenate, 

 and lead arsenate alone were tried out by spraying different plots with 

 each of these three mixtures on a succession of dates, beginning June 25 

 and continuing at intervals of 5 to 10 days thereafter (fig. 2). 



To determine the best time for treatment, the first application of the 

 Bordeaux-mixture-lead-arsenate combination was made upon different 

 plots at successive dates. The first application was made on June 25, just 

 as the first true leaves had opened on the cucumber plants, and at each 

 succeeding application a new plot was added. In every case a check 

 plot was left between the two successively sprayed plots. In field 2 

 each plot consisted of three parallel rows, each row 21 feet long. In 

 field I the plots were about twice this size. The first three applications 

 of Bordeaux mixture were made with a weak suspension (2:2: 50) in 

 order not to injure the young plants, but in the later treatments the 

 strength was gradually increased to the 4 : 6 : 50 formula. In all cases 

 where lead arsenate was used it was applied at the rate of 2 pounds to 

 50 gallons of liquid. No appreciable injury from any of the spray 

 mixtures was observed. 



The relative amount of control effected in field i at different dates of 

 appHcation is graphically shown in figure 3. 



The spray treatments were conducted as follows: Plot i (fig. 3a) 

 received its first application of Bordeaux and lead arsenate on June 25, 

 and additional sprayings at intervals of 5 to 10 days throughout the 

 season. In plots 2, 3, and 4 (fig. 3, b, c, and d), the first applications 

 were made on July 6, 14, and 19, respectively, and further sprayings were 

 made at intervals of 5 to 10 days as in plot i. It will be noted that most 

 of the infections had occurred before the third treatment, July 14, for in 

 plot 3 and its corresponding check the number of wilted plants was about 

 the same. In the first two plots there was much less wilt than in the cor- 

 responding unsprayed plots, the first sprayed plot showing by far the 

 best results. There would be a still greater difference between plot i and 

 its untreated check were it not for the facts that the latter was only about 

 three-fourths the size of the sprayed plot and that it received one applica- 



