424 BOARD OF AGRICULTURE. [Pub. Doc. 



frequently become wilted. It is caused in many cases by 

 bacteria, which multiply so rapidly in the plant as to clog 

 up the vessels. Since there are certain worms which aft'ect 

 the roots and stems of cucumbers that also cause wilting 

 and subsecjuent collapse of the plant, care must be taken to 

 distinguish between these two trou])les. If the wilting is 

 caused b}^ worms, an examination of the roots will sliow their 

 presence ; whereas, if caused by bacteria, the roots ma}^ 

 appear perfectly healthy. If the wilt is caused by bacteria, 

 sections of the leaf petiole about one inch long, placed 

 under a tumbler, or in an}" moist place, will exude a muci- 

 laginous material from their ends. This constitutes a rough 

 method of diagnosing the disease, the exudation being 

 caused by the bacteria nuiltiplying so rapidly in the tissues 

 that they are forced out. No eftective remedy is known for 

 the bacterial wilt at the present time. 



Other Troubles. — Some other difficulties which growers 

 of greenhouse cucunibers have to contend with are caused 

 by organisms belonging to the animal kingdom, such as 

 aphis, thrips and nematode or gall-forming worms. Fumi- 

 gation with tobacco is the general method of treatment 

 emi)loyed for the two former pests, Avhile freezing or steril- 

 izing the soil constitutes efficient remedies for the extermi- 

 nation of nematode worms. 



