CARNATION WILT DISEASES 13 



where the cutting has been removed may become infected with the Fusarlum 

 root rot fungus and cause the wilting of the branch. Since the dieback of the 

 shoots and wilting sometimes occur in consequence of spore-infected snags or at 

 injured axils in the branches, it is apparent that the cuttings become inoculated 

 on the stock plants with any one of several pathogenic organisms though they 

 may appear healthy and desirable for propagation. 



Growers were requested to collect batches of cuttings as if for their own propa- 

 gation and to submit them to the writer for study. Laboratory examination 

 revealed discolored tissue about the nodes in some instances. Transfers of tissue 

 from the nodes and base of the cuttings were made to sterile culture media in 

 petri dishes. Both Fusarium and Alternaria were occasionally obtained (Table 2). 



The greenhouse atmosphere and growing beds of a carnation range are obviously 

 never completely free of pathogenic fungi, however healthy the flowering stock 

 may appear. The avoidance of diseased areas in a range showing more or less 

 disease is not so completely effective in preventing the transfer of contamination 

 as selection in an environment of generally healthy stock. The population of 

 the fungus in the environment of the plants bears some relation to the extent of 

 the disease. Thus a greenhouse kept sanitary by the successful control of disease 

 is obviously important in relation to propagation. The transmission of patho- 

 genic organisms either as hidden infection or as spores lodged on the cuttings 

 can be serious, and unless it is adequately combated, desirable effective control 

 measures in later stages of culture can be defeated. 



PREPARATION AND DISINFECTION OF CUTTINGS 



Trimming 



Carnation cuttings are frequently inserted in the sand without trimming or 

 further preparation. A smooth, horizontal cut with a sharp knife at the base of 

 the cutting to remove the loose remnants of tissue has been advocated (71, 72, 76) 

 on the presumption that a jagged, sloping surface encourages an uneven for- 

 mation of roots and increases the risk of decay. Our growers also obtain satis- 

 factory results from a clean diagonal cut, which gives a larger area for the growth 

 of roots. Lamborn (39) wrote that the slips can be broken off with the fingers 

 and put directly in the cutting bed without the use of a knife and they will root 

 as certainly as if trimmed and smoothly cut at the end. Rooting the cuttings 

 without trimming them is time and labor saving, but trimming makes it possible 

 to plant more cuttings in a given area of sand. The extra operation of trimming 

 the cuttings is desirable since it offers the opportunity of scrutinizing them and 

 discarding any showing imperfections. There appears to be no evidence against 

 either method so far as disease is concerned. 



Soaking in Water 



The practice of soaking carnation cuttings in water before they are planted 

 can be the means of spreading disease, especially if the cuttings are infected or 

 come from infected stock plants or contaminated areas in the benches. In water, 

 the cuttings generally may become inoculated by spores freed from a single 

 diseased cutting, and outbreaks of carnation rust in the young stock result from 

 this practice. Creager (22) reported that the soaking of carnation cuttings in 

 water contributed to the spread of bacterial wilt caused by Phytomonas cary- 

 ophylli Burk. among the young stock. Kirby (36) reported that soaking cuttings 

 for one hour caused 18 percent of them to become infected with Alternaria in 

 contrast to 92 percent of those soaked 4 hours. 



