16 
SYSTEMIC DISEASES 
There are five diseases that can be classed as systemic, that is, the organism may be found in all parts 
of the plant: Fusarium wilt, Bacterial wilt, and three virus diseases, mosaic, streak and yellows. 
FUSARIUM WILT 
SYMPTOMS: Plants infected with Fusarium may show symptoms at any stage in their development. The 
first indication that a plant. is affected with Fusarium wilt is a slow withering of the shoot. Often 
this is apparent on only one side of the plant and in young plants this results in a twisting and dis- 
tortion of the plant. This wilting is usually accompanied by a change in color. First the leaves and 
stems change to a lighter gray-green and finally to a pale straw yellow. When infected stems 
are split, a brownish discoloration appears in the vascular tissue from the base upward. Extensive 
rotting of the roots usually does not occur until very late stages of the disease. 
The fungus responsible for this disease can live in soil in the absence of carnations, so new infec- 
tions can occur when healthy plants are planted in infested soil in the greenhouse or in the field. 
Cuttings from infected plants may also carry the disease. Infection usually takes place through the 
roots but it may also take place through wounds in the base of the main stem. Infections develop 
most rapidly at 75°-80° F. and at this optimum temperature for the disease the amount of infec- 
tion is increased, the incubation period is shortened, and the rate of killing of infected plants is in- 
creased. Symptoms appear in 12 to 75 days following infection. 
CONTROL: Complete rogueing of infected plants together with very careful selection of propagating 
material will help hold this disease down. Growers who are very serious about eliminating this 
disease should either culture stock for a propagating block or should pot-grow a few carefully se- 
lected plants and their progeny for a period of at least one year to be sure that the plants are 
not diseased, and then use them as a nucleus for further propagation of the variety concerned. 
The pots should be well spaced and extreme care should be exercised in avoiding recontamination. 
A complete program of steam sterilization should be followed to completely eliminate this disease. 
Do not transport soil from old benches to new after soil sterilization. 
Portion of lower stem and root of plant affected with Rust pustules on leaves. 
Fusarium wilt. Brown streak was evident in vascular 
tissues of the stem. Root System is intact. 
