SCIENCE'S WARFARE ON FRUIT TREE PESTS 225 



limbs may be sufficiently injured to cause them to die. Severest injury 

 is done to the tops where there is the tenderest and most rapid growth 

 as in grafts and water spouts. 



Prevention 



Prevention is nearly always better than the cure. Great care should 

 be taken, therefore, when setting out a new orchard, to prevent the 

 introduction of this louse. Orchards are usually infested by the lice that 

 are upon the roots of the nursery trees when they are set out. All 

 nursery stock should be thoroughly disinfected either by fumigation with 

 hydrocyanic acid gas, or by very thorough spraying of the trees, both 

 roots and branches, before they are set, with one of the remedies 

 mentioned below for spraying tops. 



If nursery stock is received with roots, "puddled," covered with 

 mud, the purchaser should insist upon this mud being thouroughly 

 washed off, and the roots treated for wooly aphis, as this is one of the 

 methods that the nurseryman has of covering up wooly aphis upon his 

 nursery stock. 



To prevent the spread of the wooly aphis from tree to tree and 

 orchard to orchard, the lice should be well cleaned out of the orchard 

 before the f> week of September, as it is about this time when the 

 Winged lice begin to fly about to spread the species. 



Remedies AbOTe Ground 



Wherever this louse can be reached by sprays it may be destroyed 

 like other plant lice, but one precaution is necessary, the spray must 

 be applied with sufficient force to remove or penetrate the woolly cover- 

 ing. There are several spray materials that we have found entirely 

 successful when thoroughly applied to this insect. 



Kerosene Emulsion. — According to our experience, a good kerosene 

 emulsion has no superior for the destruction of this insect. It seems 

 to penetrate the woolly covering rather better than most other in- 

 secticides. When used in the ordinary strength (one-fifteenth oil) we 

 have always found it efficient. In the proportion of one-twentieth oil 

 (5 per cent), we have usually found it sufficiently strong if applied with a 

 good deal of force and thoroughness. To be most successful, apply as a 

 moderately coarse spray and with a pressure, if possible, of 140 or 180 

 pounds. 



Soaps. — We have found the standard whale-oil soaps, such as 

 "Good's Whale Oil Soap" and "Bowker's Tree Soap" quite effectual for 

 the destruction of this louse when used in the proportion of one pound of 

 soap to each six or eight gallons of water. 



Black Leaf.— The Kentucky Tobacco Product company of Louisville, 

 Ky., manufactures a tobacco extract which they sell under the above 

 trade name, and which has become very popular among the orchardists of 

 Delta county, Colo., as a spray for orchard plant lice. We have tested 

 it quite thoroughly and have found it very efficient for the woolly aphis 



