EXPERIMENT STATION BULLETINS. 601 



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article that will not turn to a jelly when dissolved at this rate, for jellied 

 soap is very difficult to spray. The above strength, two pounds to a 

 gallon, should never be applied except in the winter when the trees 

 are entirely dormant, for an application when the buds are swelling or 

 when the leaves are on the tree is sure to do great injury to the tree. 



PYRETHRUM. 

 (Buhach or Persian Insect Powder.) 



Pyrethrum is a powder made by grinding the heads of a plant re- 

 sembling our daisy. It is produced in great quantities in California, 

 where it is sold under the proprietary name of "Buhach." It is also 

 imported from Persia and known as "Persian insect-powder." Now, the 

 insecticidal value of the Pyrethrum lies in an oil which readily passes 

 off into the air, and to prevent the loss of this the powder should always 

 be kept tightly sealed in metal cans. Insect-powder that has been ex- 

 posed for sale in open cans in drug-store windows is next to worth- 

 less, and should on no account be purchased. This insect-powder is 

 harmless to all animals breathing by means of lungs. It can be used 

 either dry or in the form of an alcoholic extract. To apply it dry, dust 

 the powder on the insects either by means of a bellows or in some other 

 way. To apply in the form of an extract, place four ounces of the powder 

 in a pint of alcohol, leave it for a week and filter, then dilute once with 

 water, and apply with an atomizer. 



HELLEBORE. 



White hellebore is the powdered root of a plant. It kills both by con- 

 tact and as an internal poison. It may be applied either dry or in the 

 form of a liquid. When used dry it should be mixed with three or four 

 times its weight of flour or plaster and then dusted on the insects. Ap- 

 plied wet, one pound should be mixed with twenty-five gallons of water 

 and this liquid applied as a spray. A convenient form of duster is made 

 as follows: A tin box like a pepper-box, holding a quart or less, is 

 fastened to a stick about six feet long by means of a screw running 

 through the bottom of the box into the stick. The cover of this box 

 should be finely perforated to allow the poison to come out very slowly 

 when shaken. This box can then be shaken over the infested plants and 

 the insects peppered or dusted with the poison. 



Hellebore is especially useful against all moist-bodied insects, such as 

 currant-worms, pear and cherry-slugs, etc., for the poison sticks to their 

 bodies. 



THE GASOLINE BLAST. 



During the season of 1807, an apparatus was devised for burning 

 scale insects on the tree. An ordinary gasoline blast-lamp or soldering 

 torch such as is used by plumbers was fitted with five parallel burners so 

 arranged that a broad sheet of flame about ten inches wide could be 

 directed on the tree. A torch of this sort was made for the writer in the 

 fall of 1807 and during the winter several tests were made. 

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