BACTERIAL, WILT OF CUCURBITS. 17 



Experiments of 1917. — In August, September, and October, 1917, 

 at Tuxedo, Md., about 5,000 of these two species of cucumber beetles 

 were collected. Special care was taken not to injure the beetles in 

 any way, and they were placed at once in the cages (PI. II, fig. 1) 

 standing in the fields where they were caught. Three species of 

 cucurbits were growing in these cages and also corn in a few of them. 

 Some of the cucurbits were inoculated with the wilt organism and 

 others were left uninoculated. After the growing plants in the cages 

 had died, squashes and other cucurbit fruits were fed to the beetles 

 until November, 1917. A few of these cages were destroyed by 

 winds during the succeeding winter, but in the 13 remaining intact 

 not a single beetle appeared in the spring of 1918. It might be 

 added, however, that in one of these cages into which several squash 

 lady bird (Epilachna borealis) had been introduced the preceding 

 fall, three live individuals were found in May, 1918. 



These attempts at hibernation of wilt-fed cucumber beetles under 

 experimental conditions have been rather discouraging, since, so 

 far as ascertained, none have lived longer than six weeks under the 

 hibernation conditions used. 



On the other hand, striped cucumber beetles collected at the same 

 time and place for the direct wilt-transmission experiments in the 

 warm air of the greenhouse have frequently been kept alive and 

 active in small cages (PI. I) for three to five months, and in two cases 

 for more than six months (Oct. 4, 1916, to Apr. 28, 1917). These 

 beetles were fed upon potted young cucumber plants which were 

 frequently changed, and they were under almost daily observation. 



DO THE WILT BACTERIA WINTER OVER IN THE SOIL? 



Experimental carrying of the wilt organism through the entire 

 winter by the beetles has failed, on account of our inability to keep 

 the beetles alive for that length of time under the hibernation con- 

 ditions given. However, the problem has been attacked from other 

 angles and some further evidence has been accumulated to show 

 that the striped cucumber beetle may be a winter carrier of Bacillus 

 tracheipMlus. 



In eastern Long Island the previously reported 1 cage experi- 

 ments were repeated during the summer of 1916. In the original 

 experiments (1915) 50 large, wire-covered cages (PI. II, fig. 2) were 

 set in two fields where during the preceding season about 75 per 

 cent of the cucumber plants had been infected with wilt. In Sep- 

 tember, 1915, and again in May, 1916, the soil in one-half of these 

 cages was heavily inoculated with well-water suspensions of tested 

 virulent wilt bacteria. No beetles were introduced, and not a single 



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

 142179°— 20— Bull. 828 3 



