No. 6. DEPARTMENT OF AGRICULTURE. 407 



"The soap, first finely divided, is dissolved in the water by boiling 

 and immediately added boiling hot away from the fire to the kero- 

 sene. The whole mixture is then agitated violently while hot, by 

 being pumped back upon itself with a large force pump and direct 

 discharge nozzzle throwing a strong stream, preferably one-eighth 

 iiich in diameter. After from three to five minutes pumping the 

 emulsion should be perfect and the mixture will have increased from 

 one-third to one-half in bulk and assumed the consistency of cream. 

 Well made, this emulsion will keep indefinitely, and should be diluted 

 only as wanted for use.'' To use it, add six gallons of water to a 

 gallon of the emulsion or at that rate. If hard water must be used 

 either in making or in diluting the emulsion for use, add about one- 

 quarter more soap. Spray long enough to thoroughly wet the bark, 

 but not long enough to let the emulsion stand in the crotches in little 

 pools as this would have an injurious effect upon the tree. 



PLANT LICE. 



(Aphididae.) 



Plant lice or Aphids are alwaj's an important pest to crops and to 

 flowers as well. They appear early in the spring, often before the 

 plants they feed upon have made a good start, and as they multiply 

 with great rapidity, sometimes cause much loss. 



Nearly every plant, shrub and tree has one or more kinds of plant 

 lice which attack it, and in seasons favorable to their rapid increase 

 may so check growth as to seriously injure the crop. 



Among the most important plant lice with which the farmer and 

 fruit grower come in contact are the wooly apple louse, often present 

 along scars on apple limbs in the fall, and very noticeable because 

 of the white wooly threads it produces; the green apple louse, often 

 so abundant in spring on the leaves; the black louse on the plum; 

 the wheat Aphis; the pea-vine louse; the cabbage louse; the currant 

 louse; the rose louse and the corn Aphis. 



In many cases the first evidence of the presence of plant lice is the 

 curling of the leaves which is often particularly noticeable on cherry 

 and plum trees in May. Often, however, the plant lice are not seen 

 in large numbers till later, in the summer or even fall. 



Life History. 



No accurate description of the life history of plant lice in general 

 can be given, as different species of these insects have different 

 histories. A few general facts, however, will apply to nearly all. 



In a general w^ay it may be stated that plant lice pass the winter 



