326 Diseases of Greenhouse Crops 



trol of the disease. Furthermore, the disease may 

 be kept in check by dusting with sulphur-arsenate 

 made of a mixture of ninety parts finely ground 

 sulphur and ten parts powdered arsenate of lead. 

 A lime sulphur solution composed of one part of 

 the commercial concentrate solution to fifty parts 

 of water is as efficient in controlling black leaf spot 

 as is Bordeaux or sulphur-lead-dust. It is purely 

 for the florist to decide whether he wishes to spray 

 or to dust. The sulphur-arsenate may be applied 

 with an efficient little machine known as the Corona 

 hand duster. The same material is also very effi- 

 cient for controlling the powdery mildew of the 

 rose. In this case, too, the work of Massey has 

 shown that sulphur-arsenate is even more efficient 

 than lime-sulphur solution 1-50, or Bordeaux mix- 

 ture 5-5-50. 



Anthracnose 



Caused by Glceosporium roscz Hals. 



Symptoms, The chief feature of this disease as 

 observed by Halsted is a premature dropping of 

 the foliage. Some stems may be entirely bare while 

 others may have a few leaves still clinging to them. 

 Infection may start on the leaves first, in which case 

 they drop off, and soon develop the salmon-colored 

 pustules on the dead spots. Generally, however, 

 the trouble starts at the tender branches and works 

 its way downwards. If infection takes place at a 



♦Halsted, B. D., New Jersey Agr. Expt. Sta., Fourteenth Rept.: 

 401-409, 1893. 



