
Chrysan tigen “um Sia 
For the past three or four years a new trouble of chrysanthemums known as stunt has been observed. 
At first, this irregularity was confined to a few varieties but in the 1947 and 1948 season almost all 
varieties were observed to carry a percentage of stunt. This trouble has been observed in all areas 
producing chrysanthemums. 
SYMPTOMS OF STUNT 
Prof. A. W. Dimock, Cornell University, describes stunt as follows: "As with all other diseases, symp- 
toms of stunt vary with the variety, but the following have been more or less consistent: (a) the 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; (b) 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; 
(c) 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; (d) with varieties possessing red 
pigment (the bronzes, pinks and reds) the red component of the color is badly bleached; (e) with 
some varieties the blossoms may be greatly reduced in size." 
CAUSE OF THE TROUBLE 
Almost all of the research institutions are spending considerable time trying to find the cause of stunt. 
Dr. Philip Brierley and Dr. Floyd F. Smith, U.S.D.A., Beltsville, Md., have fairly good evidence that it 
is a virus. They have shown definitely that it is transmitted with cuttings taken from diseased stock. 
In addition, spread has occurred from diseased varieties to others not previously affected, indi- 
cating that it has been transmitted by an insect or through manual means. Just what insect or manual 
handling involved is not yet known. Stunted plants have never been known to reproduce anything but 
stunted plants. 
Many ideas as to the cause of stunt have been proposed such as, over propagated stock, lighted 
stock, hormone treatment, not allowing the stock to flower and many others. After observing the 
spread of stunt in various establishments where the treatment of stock was the same used for years, 
it is impossible to lay the cause to anything but a virus. 
If the healthy plants are selected after flowering from a lot where stunted plants were present 
it is known that the next generation will likewise be badly stunted. This indicates that the virus is 
already in those normal bloaming plants. 
CONTROL MEASURES 
Not knowing how stunt is spread from plant to plant and how long the incubation period is, makes it 
difficult to set-up a definite control measure. But by assuming that an insect or that manual opera- 
tions carries this trouble the following suggestions have been recommended by research investigators. 
(1) Select only the healthiest plants in June or early 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 insecticides. (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 
history on each clon. 
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 
chrysanthemum cuttings to carry out this extreme control measure. 

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