BACTERIAL WILT OF CUCURBITS. 6 



been tested so fully, but sufficient work has been done to show that 

 they are also capable of direct wilt transmission. 



TRANSMISSION FROM RANDOM COLLECTIONS OF BEETLES. 



Collections of striped cucumber beetles and 12-spotted cucumber 

 beetles taken at random in the fields have given widely varying 

 results as to wilt transmission according to time of year, prevalence 

 of wilt, amount of territory devoted to cucurbits, and length of time 

 the beetles had fed since attaining the adult stage. In eastern Long 

 Island from the first collections of early spring only an occasional 

 striped beetle has proved to be a wilt carrier. Later in the season 

 some collections have shown a large percentage capable of spreading 

 the disease. For example, on September 1, 1916, striped beetles 

 were collected at random in a cucurbit field and several put into each 

 of four beetle-proof cages containing healthy cucumber plants. Many 

 of the vines in each of the cages contracted bacterial wilt, so that at 

 least one of the beetles introduced into each cage must have been a 

 wilt earner. About two weeks previously six beetles collected in the 

 same locality failed to give infection. In this locality late cucumbers 

 constitute one of the main crops. 



However, in the trucking sections around the District of Columbia 

 late cucurbits are rather the exception, most of these crops being 

 planted there in early spring. In that locality random collections 

 from the field have given a much smaller percentage of infection. 

 During the summer of 1917, at Tuxedo, Md., from five to seven large 

 insect cages were kept constantly as storage cages for both species of 

 cucumber beetles. Healthy plants grown in the cages and healthy 

 potted cucumber plants brought frequently from the greenhouses at 

 Washington, D. C, were kept in the cages as food for the beetles. 

 Collections of beetles made at frequent intervals from fields where 

 wilt was present were placed in these cages, but throughout the season 

 only two cases of wilt occurred in these cages. In many instances 

 the beetles were taken directly from wilting vines. 



Twelve striped beetles, among the first of the season found, were 

 collected May 20, 1918, in an early cymling field at Kenilworth, D. C. 

 Careful search over the field failed to reveal any cases of wilt. These 

 beetles were caged for four days with 10 cucumber seedlings, after 

 which the plants were held for observation in a beetle-free cage. On 

 June 4 two of the ten plants had wilted. Cultures were made and 

 Bacillus traclieipMlus was isolated and tested by successful inocu- 

 lations. 



In a large collection of striped beetles made at Norfolk, Va., about 

 October 1, 1916, wilt resulted in one out of several cages among which 

 the beetles were distributed. 



In most instances only a very small proportion of the cucumber 

 beetles present in a field actually carry infection. 



