INSECTS, DISEASES AND OTHER PESTS 243 



be in the soil brought in from the field. Healthy plants 

 put in infected soil will be killed in from two to four weeks, 

 depending on temperature and light. Experiments show 

 that the fungus will grow through the soil at the rate of 

 one-half inch every 24 hours, which makes it simply a 

 matter of a few days, comparatively speaking, until the 

 neighboring plants, and finally the entire bench, has become 

 infected. 



As a rule most of the growers bench Carnation plants 

 in August, when the temperature is still quite high. This 

 condition in itself seems to be the most important factor 

 in the spread and development of the disease, especially 

 during the first month after the plants are transplanted. 

 Again when the steam is turned on in the houses the number 

 of stem rot plants will increase materially. During the 

 Winter very little stem rot will develop if cultural condi- 

 tions are good. However, when the temperature rises in 

 the Spring and the steam is turned off, another point in 

 the life of the plant is reached when it is very susceptible 

 to disease. The low vitality of the plant at this period is 

 responsible, in the main, for such a condition. 



The successful passing over of the three most critical 

 periods in the life of the plant in the house depends a great 

 deal on the temperature. Of course, it is very hard to 

 control the temperature at these points, but with careful 

 attention to ventilation and cultural conditions, these 

 periods may be tided over without serious injury. 



One of the most important factors in the control of 

 stem rot in the greenhouse is the careful selection of Carna- 

 tion plants when brought in from the field. Any plant 

 that shows the least signs of disease, as well as all unhealthv 

 or damaged plants, should be discarded. The matter of 

 selecting plants is, therefore, of prime importance, in fact 



