CHRYSANTHEMUM CUTTINGS 
Diseases and Their Control 
VIRUSES 
The word ''virus"’ is being referred to by the medical profession as well as by. the florists and a short 
explanation of virus should prove of interest. 
Viruses of the chrysanthemum are considered to be infectious; that is they can be transmitted to a 
healthy plant only by contact with an infected plant. They are not carried in the soil, water or air as are 
other diseases caused by fungi and bacteria. 
The virus particles cannot be seen by the most powerful microscopes. Most of them will pass through 
bacterial filters. They respond like living organisms. They are always present in the sap of diseased 
plants and can be transmitted to a healthy plant through wounds or by mechanical means. The 
chrysanthemum is known to be attecied with three viruses, namely yellows, mosaic and stunt. Stunt 
is the only one that has caused much concern. It has been found that aphids as well as mechanical 
handling will cause stunt to spread. 
Once a plant is infected with a virus it usually always remains affected. To define a virus the follow- 
ing is as good as any: A virus is a protein which requires the presence of living cells for multiplication 
and it causes changes in the structure and functions of living cells. 
STUNT 
SYMPTOMS. Young foliage may be paler than normal and has a tendency to more upright growth 
rather than growing at a wide angle with the stem. Diseased plants show stunting in growth 
after they have been in the soil a few weeks, and at maturity they may in some cases be less 
than half as tall as normal. Buds may form and blossoms open a week or 10 days ahead of 
those on healthy plants, although on some varieties stunted plants will bloom after the normal 
plants. Varieties possessing red pigment (the bronzes, pinks and reds) the red component of the 
color is badly bleached. With most varieties the blossoms are greatly reduced in size. 
CONTROL. Knowing that stunt is a virus and that it can be spread by insects as well as manual 
operations the following recommendations for its control are necessary. (1) Select only the health- 
iest plants in June or July for stock purposes. (2) Use a sterile knife when removing cuttings or 
pinching the plants. (3) Keep all insects from these plants by isolation and use of good insec- 
ticides. (4) Rogue out all plants from time to time that look the least bit weaker. (5) Be careful 
not to bruise or handle the plants. (6) Use single plant selection procedure and keep case his- 
tory on each clon. (7) Do not attempt to increase population until mother block of stock plants 
is entirely free from diseased plants for at least two generations. 
Realizing that such a procedure to keep stock clean from stunt is very expensive and that all growers 
cannot carry out these control measures it is therefore, necessary for the propagators of chrysanthe- 
mum cuttings to carry out this extreme contfol measure. 
DODDER 
SYMPTOMS. Dodder is a parasitic twiner, bearing 
clusters of small flowers. They are leafless annuals, 
with very slender yellow, white or red stems, which 
become attached to the plant by means of root-like 
suckers. Dodder is occasionally found on chrys- 
anthemums and will cause a complete loss of crop. 
CONTROL. Dodder is common in low, weedy 
places and may be carried into the greenhouse in 
the soil or manure. Soil sterilization is the only pre- 
vention. After dodder is attached to the plants 
remove the affected plants and burn. 
Stunt in Harvester 
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