5G 



Lessons in Fruit Growing. 



with hyclroc3'anic gas.* Infested orchard trees may be 

 sprayed in winter with a solution formed by dissolving two 

 pounds of whale-oil soap in one gallon of hot water; or 

 ■with undiluted crude petroleum of a specific gravity of not 

 less than 43° Beaurae. A single spraying is not likely to 

 destroy all of the insects on a badly infested tree, hence 

 it is often necessary to repeat the treatment the following 

 winter. Summer sprayings may be made with strong to- 

 bacco water or a mechanical emulsion containing ten per 

 cent, of kerosene. 



61. The woolly-louse or woolly-apMs of the apple (S'c/?/- 

 zoneura lanigera) (Fig. IG) is injurious in two forms, in 

 one form attacking the trunk of 

 the tree, and in the other the 

 roots. Both forms infest apple 

 trees of all ages. In spring the 

 presence of the insect is indicated 

 by small bluish-white specks re- 

 sembling mold, about the base of 

 the shoots growing from the 

 trunk, about the base of the trunk 

 itself, or about recent wounds in 

 the bark. Later, the cottony coat- 

 ing of the insect becomes more dis- 

 tinct and adheres to the fingers when touched. In autumn, 

 the insects commonly cluster about the axils of the leaves 

 toward the end of the twigs, sometimes appearing in such 

 numbers as to make the tree look as if whitewashed. The 

 lice derive their nourishment from the sap of the tree and 



' The method of preparing this gas is described in " Principles of Plant Cul- 

 ture." The trees are exposed 45 minutes to the gas formed by mixing 1 fluid 

 ounce each of sulfuric acid and fused potassimn cyanide (98 per cent, pure) with 

 two fluid ounces of water for each 125 cubic feet of space in the fumigating room. 



W#' 



Fig. 16. Woolly-louse of ap- 

 ple. (Cut from U. S. Depart- 

 ment of Agricultiu-e.) 



