June 12. 1916 Bacterial Wilt of Cucurbits . 423 



a depth of 7 inches were made at numerous points over this squash field. 

 Considerable numbers of dormant beetles were found under clods, old 

 vines, mummied squashes, and around the bases of old squash stems 

 just beneath the soil surface. No beetles were found below the first 2 

 inches and most of them were found at a depth of less than i inch. 



SOriv TRANSMISSION 



In the experiments of 191 5 at East Marion, Long Island, N. Y.,^ bacterial 

 wilt was not transmitted to the plants from the soil, although in the 

 same fields during the preceding season the crop had been largely 

 destroyed by this disease. In a large number of greenhouse inocula- 

 tions into one of two or more cucurbit plants in a single pot (seven 

 experiments, including in all 126 pots), none but the inoculated plants 

 ever took the disease, although the latter wilted to the ground, and the 

 pots were kept under obser\'ation from one to three months. The 

 house was free from cucurbitaceous insects. 



In addition to these observations and experiments relative to soil 

 transmission three series of direct soil inoculations were made: 



Series of March 18, 1915. — Thirty-two Arlington White Spine forcing 

 cucumber plants 4 to 5 inches high, transplanted March 9 and not dis- 

 turbed from that date until the date of inoculation, were inoculated as 

 follows : 



Eight cucumber plants not root-pruned and the same number of plants 

 root-pruned were inoculated with strain R230 by pouring on the soil beef- 

 bouillon cultures 6 days old. Sixteen plants were inoculated in the 

 same way with strain R235. Sixteen plants were root-pruned and the 

 soil moistened with tap water only, these plants being held as checks. 

 The cultures used were tested as to virulence by needle-puncture inocu- 

 lations into the leaves of several cucumber plants of the same age and 

 variety. 



All plants inoculated by needle puncture promptly wilted. 



On April i the 16 inoculated plants which had been root-pruned showed 

 two cases of wilt. No wilt was evident in the 16 non-root-pnmed plants 

 at this date. 



On April 12, among the 16 root-pruned plants there were 10 wilted 

 and among the 16 non-root-pruned there were 2 wilted. The 16 check 

 plants (root-pruned) showed no signs of wilt. 



Isolations were made from all plants showing infection from the 

 soil, and these cultures produced wilt promptly upon inoculation into 

 leaves of healthy plants. 



The experiment was continued for two months from the date of 

 inoculation, but no further cases of wilt appeared. 



Series of March 31, 191 6. — Sixty Chicago Pickling cucumbers 

 planted January 28, 191 6 (transplanted once), in pots in the greenhouse 



> Rand, F. V., 1915. Op. cit. 



