349 



In large buildings, it is frequently necessary to suspend the bags of cyanide over the 

 jars by cords running through screw eyes and all leading to a place near the door. 

 By cutting all the cords at once the cyanide will be lowered into the jars and the 

 operator may escape without injury. Let the fumigation continue all night, lock- 

 ing all outside doors and placing danger signs on the house. 



No general formula can be given for fumigating the different 



kinds of plants grown in greenhouses, as the species and varieties 



differ greatly in their ability to withstand the effects of the gas. 



Ferns cuid roses are very susceptible to injury, and fumigation 



if attempted at all should be performed with great caution. 



Fumigation will not kill insect eggs and thus must be repeated when the new brood 



appears. Fumigate only at night when there is no wind. Have the house as dry 



as possible and the temperature as near 60° as practicable. 



Fumigation of 

 greenhouses. 



IV. THE CONTROL OF PLANT DISEASES. 



H. H. WHETZEL AND F. C. STEWART. 



ALFALFA. 



This disease causes 



Dodder. small areas of alfalfa 



to die. Around the 



margins of these areas the ground is 



covered with a tangled mat of yellow 



threads that twine closely about the 



plants and kill them (Pig. 161). 



Infested spots should be closely 



mowed; the stubble sprinkled with 



kerosene, covered with dry hay 



and burned. Only seed free from 



dodder should be used. Samples of 



seed may be sent the Geneva Experi- 

 ment Station to be examined for dodder. 



Alfalfa seed can be cleaned by sifting 



through 20x20 mesh sieve made of No. 



34 wire. See Geneva Circular No. 8. 



This is the most 

 Leaf-spot. serious fimgous dis- 

 ease of the crop in the 



State. It causes the leaves to become 



spotted and yellow and to fall pre- 

 maturely. New seeding when badly 



diseased, should be topped,"6jri Txever 



mowed closely. When older fields are 



attacked, the hay should be cut a few 



Says early to avoid loss of leaves and 



to permit a new growth that will usually outgrow the trouble, 



Fig. 161. Dodder on alfalfa, showing the 

 slender cord-like stems and the bunches 

 of small white flowers. 



(Pig. 162.) 



