14 MASS. EXPERIMENT STATION BULLETIN 427 



In view of the continual redistribution of spores among the stock plants in 

 the benches by water, air currents, or even cultural practices, some infection is 

 possible among apparently clean cuttings. It would seem best either to wash 

 the cuttings under a spray of cold water or to soak them briefly in water and 

 then allow the water to drain off. Subsequently they might be kept moist in a 

 cool atmosphere until they can be trimmed and planted. Cuttings soaked in 

 water for several hours do not root well and can be a total failure. 



Disinfecting Chemicals 

 Action on Fungous Spores 



The presence of spores of pathogenic organisms on the cuttings suggests the 

 desirability of disinfecting them before they are placed in the sand. A chemical 

 disinfectant for this purpose must meet certain rigid requirements. It must not 

 inhibit rooting or injure the cuttings in any way. The treatment would be 

 advantageous if it could hasten and improve rooting in addition to providing 

 some degree of disinfection. The toxicity of many chemicals to the conidia of 

 the Alternaria blight fungus and of other organisms pathogenic to carnations was 

 studied (Fig. 5). 



Small pieces of diseased carnation plant tissue bearing spores of Alternaria 

 dianthi, Fusarnmi dianthi, and Uromyces caryophyllinus and of tomato leaf 

 tissue bearing spores of Cladosporium fidvum Cke. were immersed in solutions of 

 certain chemicals selected for their mild fungicidal properties, in the effort to 

 find a safe treatment offering some degree of disinfection. The small pieces of 

 sporulating tissue were immersed and soaked for a period of 5 to 15 minutes, 

 then washed with fresh water and drained, and then incubated at laboratory 

 temperature. 



Solutions of potassium permanganate varying in concentration from saturation 

 to 1-2,000 were tested. This chemical is a mild fungicide, and has some use for 

 that purpose in horticultural practice. A saturated solution was generally and 

 consistently toxic, but as the concentration was weakened in gradual steps to 

 1-2,000 toxicity was not consistent. The results with the same solution were 

 frequently reversed and this was true of both 1-500 and 1-2,000 solutions; but 

 trials in which g ermination was completely suppressed were frequent enough at a 

 1-1,000 dilution to make it desirable for disinfecting carnation cuttings. It was 

 apparent that factors not well understood were present which accounted for 

 complete toxicity in manj' trials and incomplete toxicit}' or the absence of it in 

 others. 



Spores of Alternaria immersed in drops of potassium permanganate 1-500 to 

 1-2,000 and incubated for 48 hours, then immersed in fresh water and incubated 

 further, failed to germinate. Likewise when the spores were immersed in fresh 

 solutions for 30 to 100 minutes there was no germination. When the spores were 

 immersed in drops of 1-500 and 1-1,000 solutions on glass slides, dried in the 

 laboratory for 30 minutes, and then incubated in moist Petri dishes, the viability 

 of the spores was lost. B3' this method a 1-2,000 solution was not toxic. 



Small pieces of infected leaf areas bearing Alternaria spores were soaked in 

 solutions of potassium permanganate 1-500, 1-1,000, 1-1,500, and 1-2,000 for 

 5, 10, and 15 minutes and then washed clean with dribbles of fresh water from a 

 medicine dropper. The mounts were then immersed in a drop of fresh water 

 and incubated for spore germination. The solutions were tested for their toxic 

 effect at regular intervals after preparation. Concentrations of 1-1,500 and 

 1-2,000 were hardly toxic in the 5 or 10 minute immersion periods, even when the 

 solutions were freshly made. The tests showed almost complete loss of fungicidal 



