Threefold Program 



The floriculture crop pathology 

 research program was launched with 

 a three-way attack on these carnation 

 diseases. First, it was aimed to ob- 

 tain fundamental information on 

 virus diseases of carnations. The 

 extent of fungous and bacterial 

 pathogens in commercial plantings 

 was to be determined. The third 

 phase of the program was concerned 

 with an effective chemical control 

 for these diseases. 



Virus Properties 



Carnation mosaic virus is inac- 

 tivated by extremes of pH — below 4 

 (acidic) and above 9 (alkaline) . The 

 most effective pH for securing uni- 

 form and consistent infection in host 

 plants is neutrality (pH 7) . 



The virus may be transmitted 

 easily during various cultural pro- 

 cedures. If carnation leaf virus- 

 infected sap is diluted beyond 1:1000 

 and flower juice above 1:500, the 

 virus concentration is almost lost. 



Heating carnation virus-infected 

 sap between 145.4° and 154.4°F. for 

 fifteen minutes inactivated the virus. 

 Since carnation cuttings will not 

 tolerate this amount of heat, car- 

 nation virus must be controlled by 

 some other method. 



Culturing 



Culturing of carnations, that is, 

 placing surface-sterilized pieces of 

 carnation stems into dishes contain- 

 ing a suitable growing medium, has 

 become the ideal indexing procedure 



Left: Virus infected car- 

 nation with character- 

 istic mottling. 



Right: Healthy plant. 



Norma II Bnlteriield 



for determining infection. The meth- 

 od is so efficient that bacteria or 

 fungi can be detected in carrier hosts 

 that show no symptoms under nor- 

 mal growing conditions. Cultured 

 plants from the clean areas of the 

 greenhouse become the source of 

 supply for disease-free cuttings. 



Chemicals Give Promise 



Most fungicides are developed for 

 fiber and food crops. Adaptation of 

 these materials for control of flori- 

 culture and woody ornamental plants, 

 however, is arrived at by trial and 

 error. Since 1950, thirteen com- 

 mercial preparations have been tested, 

 and those giving promise have been 

 retested. Of these, only three mater- 

 ials have survived to the retest stage. 



These materials are evaluated for 

 their effectiveness in the control of 

 the disease organisms involved: their 

 effect on the pH of the soil, on the 

 soil fertilization program, on soluble 

 salts in the soil, on plant growth, and 

 on production and quality of flower. 

 The rates of applications suitable for 

 the crop are being determined. 



Continued research in this flori- 

 culture crop as well as other crops 

 is the only answer to the practical 

 control of disease, the outstanding 

 limiting factor in production. 



