40 BULLETIN 828, U. S. DEPARTMENT OF AGRICULTURE. 



PULLING TESTS. 



Since the cucumber beetles originally become carriers through 

 feeding on wilt-infected plants, it was thought possible that by 

 pulling the wilted plants during the early part of the season an appre- 

 ciable measure of control might be effected. Accordingly at East 

 Marion, Long Island (May 24, 1916), 200 hills of Woodruff's Hybrid 

 cucumber were planted in an isolated block, the location of which 

 is shown in figure 1, Field IV. There were 800 plants in the field 

 after thinning and at the time the first wilt appeared (June 29). 

 Wilted plants were pulled and removed from the field 1 times through 

 the season, on the following dates: June 29, July 11, 13, 18, 21, 27, 31, 

 and August 11, 18, and 25. During the course of the season 249 

 plants wilted, or 31 per cent of the total number left after thinning. 

 In the control, untreated plats of spray-test Field Ha in this same 

 locality (fig. 1) the amount of the disease varied from 45 to 56 per 

 cent, while of about 1,000 unsprayed plants in Field II (fig. 1) 60 per 

 cent wilted. Thus the control by pulling of wilted plants was 

 entirely as effective as that by the weaker Bordeaux mixture used. 



This experiment was repeated in 1917, near Tuxedo, Md., using 

 Arlington White Spine cucumbers. The number of plants left after 

 thinning was 1,046, while 332, or a little less than 32 per cent, con- 

 tracted wilt and were pulled during the season. The average wilt in 

 the three untreated plats of the neighboring spray test was about 36 

 per cent. Thus a slight difference is to be noted hi favor of pulling 

 the wilted plants, but the result is by no means so well marked as in 

 the Long Island test. However, the Tuxedo plat was located in a 

 field of cucurbits and was separated from other cucumbers and canta- 

 loupes only by a strip of watermelons 3 rods wide, while the test plat 

 on Long Island was about one-eighth of a mile from any other cucur- 

 bits, and corn and other noncucurbitaceous crops occupied the 

 intervening area. 



Clearly some measure of control is effected by the pulling of wilted 

 plants, but the presence of a neighboring field where this control 

 method is not practiced may largely nullify the good results. 



CONTROL IN GREENHOUSES. 



The senior writer has in some cases found serious damage from 

 wilt on cucumbers in commercial greenhouses. In these instances 

 the striped cucumber beetle has clearly been the first source of 

 infection, though the greenhouse workers have sometimes continued 

 the spread of the disease with much greater efficiency than the 

 original carrier. Cases have been noted where wilt infection has 

 followed down the row on one side of a greenhouse bed, taking nearly 

 every plant, while on the other side of the same bed scarcely a single 

 case could be found. • Here the evidence is clear that pruning instru- 

 ments were the carriers of infection. 



