■''l6 A DISEASE OF CUPRESSUS PLANTS. 



(2) Plants were pricked with a sterile needle and spores 



inserted in tne wounds, and the plants sprayed with 

 water and treated as in (i). 



(3) Plants were treated as in (i) except that they were 



removed from the moist chamber after two days. 



As mentioned above, no infections were obtained in No. 3. 



In both (i) and (2) typical infections were obtained, but 

 while the former took three weeks to show infection, the latter 

 took only from three to five days. From both of these the 

 organism was easily re-isolated, i'he poor results obtained in 

 the 1915 experiments were probably due to the fact that mycelial 

 growth only was used, the fruiting stage not having been obtained 

 in cultures at that time. 



From the above results, it will be seen that artificial infec- 

 tion takes place readily when the plants are first injured, but 

 otherwise with difficulty, and further, that moisture is essential 

 for the development of the disease. 



Although it has been found difficult to infect uninjured 

 plants, it seems unlikely, considering the rapidity with which the 

 disease spreads, that the fungus depends on wounds for 

 entrance. Unless rain and wind cause injuries by the plants rub- 

 bing against each other, the wound theory seems hardly tenable. 

 Further experiments are necessary to establish the method of 

 irjfection. 



Control Measures. 



With a view to finding out some means of controlling the 

 disease by spraying, the sensitiveness of the fungus to copper 

 salts was tested. Spores were germinated in different solutions 

 of copper sulphate, and found to be highly sensitive to this salt, 

 failing to germinate in a solution containing copper sulphate in 

 the proportion of i part to 10,000 parts water. 



From the above result, it seems safe to recommend spraying 

 with Bordeaux Mixture, or other fungicides containing corner 

 salts, as an effective means of controlling the disease, although 

 actual experiments along this line are not yet complete. A pre- 

 liminary test was made in which plants were treated with 

 Bordeaux Mixture, sprayed with water containing a heavy sus- 

 pension of spores, and kept under conditions favourable for the 

 development of the disease. No infections occurred, but owing 

 to the difficulty with which uninjured plants are infected under 

 normal conditions, the test is not considered conclusive. 



General preventative measures should, of course, also be 

 taken, such as the careful preparation and care of the seed beds, 

 the selection of clean, healthy plants, care in handling when 

 transplanting, the removing and burning of diseased material, 

 and care in not overwatering the plants. 



In conclusion, it might be as well to sum up the few points 

 .in which the Phoma sp. reviewed above differs 'from that 

 described by Hahn, Hartley, and Pierce. 



The pycnidia do not appear to break out before maturity. 



