BACTERIAL WILT OF CUCURBITS. 



£9 



effective were made July 6 and 13, respectively, and it thus seems 

 apparent that the greater portion of wilt infections took place during 

 the first half of July. Reference to the beetle and wilt curves for 

 this field (fig. 3) shows that this was during the period when the 

 striped cucumber beetles were becoming less prevalent; but when 

 it is known that wilt usually appears within less than two weeks 

 after inoculation it is seen that this period of greatest probable infec- 

 tion corresponds with the curves showing the actual appearance of 

 wilt (fig. 3, II and Ila) in these two contiguous spray and cage-test 

 blocks. 



During the following season (1917) another spray test was carried 

 out near Tuxedo, Md., using Arlington White Spine cucumbers. 

 The purpose of this experiment was to compare different strengths 

 of Bordeaux mixture, as well as to gain further general evidence along 

 the fine of control. Applications of each mixture were made on 

 June 13, 18, 25, July 2, 9, 17, 23, 30, and August 6, making nine 

 treatments in all. Reference to Table II will show the different 

 mixtures used and the numbers and percentages of wilted plants in 

 the different plats. Two pounds of lead arsenate paste -were added 

 to each 50 gallons of Bordeaux mixture used. The total number of 

 plants in each plat is based on the assumption of three to a hill, 

 since they were thinned to approximately this number early in the 

 season. Wilt in this field was not quite as serious as in the Long 

 Island locality. 



Table II. — Spray experiment at Tuxedo, Md. 



Plat 

 No. 



Treatment. 



Number 



of plants 



at the 



start. 



Number ; ^Zt^' 

 of cases ■ a?, e °* 



I 



n 

 m 



IV 



v 



VI 



VII 



Bordeaux mixture plus lead arsenate, 2-3-50-2 . 



Control, unsprayed 



Bordeaux mixture plus lead arsenate, 3-4-50-2 

 Bordeaux mixture plus lead arsenate, 4-5-50-2. . 



Control, unsprayed 



Bordeaux mixture plus lead arsenate, 4-2-50-2. . 

 Control, unsprayed 



225 

 225 

 225 

 225 

 225 

 177 

 99 



16.4 

 41.7 

 15.5 

 11.5 

 35.5 

 2.8 

 30.3 



The percentage of cases in the three unsprayed plats varied from 

 30 to 42 per cent, while in the four sprayed plats only 3 to 16 per 

 cent of the plants wilted. The fungicide was progressively more 

 effective as the amount of copper sulphate was increased, the 4-2-50 

 formula reducing the wilt to about 3 per cent. However, the excess 

 of copper sulphate in this last mixture seriously burned the foliage, 

 so that its general use can not be recommended. The 4-5-50 Bor- 

 deaux mixture with 2 pounds of lead arsenate paste gives the best 

 control of any treatment we have thus far used in our experiments. 



