432 Journal of Agricultural Research voi. vr, No. h 



parts of the field and the beetles appeared here a few days earlier than in 

 field I . 



Field observations indicate that the results obtained were due to a bac- 

 tericidal and repellent action of the Bordeaux mixture and lead-arsenate 

 combination, and probably in part to an insecticidal action by the latter 

 ingredient. The beetles were less frequent on the sprayed than on the 

 unsprayed plots, and among the sprayed plants injured by beetles there 

 was apparently a smaller percentage of infection resulting than among 

 similar unsprayed plants. That is, the control effected by the Bordeaux 

 mixture alone was apparently due to its repellent and bactericidal action, 

 and that by the lead arsenate alone to its repellent and insecticidal action, 

 while the more complete control by the two mixtures together was due to 

 a combination of their bactericidal, repellent, and insecticidal properties. 



The bactericidal action of Bordeaux mixture has been further investi- 

 gated in a series of six greenhouse tests, in which sprayed and unsprayed 

 leaves of potted plants were inoculated in as nearly an identical manner 

 as possible by needle punctures from cultures of the same strain of organism. 

 The spray used was 2 13 150 Bordeaux, and this was allowed to dry 

 thoroughly on the leaves before inoculating. In most cases the plants 

 were not inoculated until 24 hours after spraying. 



In the first test, December 2, 191 5, three weeks after planting, seven 

 unsprayed and seven sprayed Chicago Pickling cucumber plants were 

 inoculated from i -week-old beef-agar slant cultures. After 15 days 

 the unsprayed plants showed 100 per cent of infection, and the sprayed 

 plants 29 per cent. 



In the same way and at the same time a test was carried out on three 

 varieties of cantaloupe — Rockyford, Sweet Air, and Baltimore Nutmeg. 

 Thirty-five inoculations were made into unsprayed plants and 37 into 

 sprayed plants. There was no apparent difference in susceptibility 

 among the three varieties used. Of these inoculations the unsprayed 

 gave 95 per cent of infection and the sprayed leaves 46 per cent. 



In a third test (Jan. 8, 191 6), Chicago Pickling cucumbers planted 

 November 13, 1915, were used. In this test 36 unsprayed and 37 sprayed 

 plants were inoculated with the wilt organism, using agar slants 9 days 

 old. After 19 days it was found that 92 per cent of the unsprayed and 

 35 per cent of the sprayed cucumbers had contracted the disease. 



A further trial was made (Jan. 19, 191 6) with 19 Chicago Pickling 

 cucumbers planted October 29, 191 5. In the case of these older cucum- 

 bers unsprayed and sprayed leaves on the same plant and as nearly of the 

 same age and appearance as possible were used for inoculation. Both 

 sprayed and unspra}'ed leaves had been dusted with flowers of sulphur 

 for the control of powdery mildew, and this treatment, together with 

 the age of the plants, considerably reduced the infection. However, 

 even here the unsprayed leaves gave 63 per cent and the sprayed leaves 

 1 1 per cent of infection. 



