312 PRINCIPLES OF SPRAYING 



mixture it is less injurious to the foliage. One pound of zinc 

 arsenite is equivalent to about three pounds of arsenate of 

 lead. 



Hellebore. — The roots of white hellebore plants are ground into 

 a powder which may be applied either dry or in a water solution. 

 After being ground it loses its strength rapidly, and should be 

 kept in a closed vessel to prevent loss of strength. It may be 

 dusted on plants in its full strength without injury. For the liquid 

 spray use four ounces of powdered hellebore mixed with two to 

 four gallons of water. An ounce of liquid glue added to this 

 mixture will aid in keeping it on the plants. 



Hellebore tea is sometimes made by boiling the roots in water. 

 While fresh this may be sprayed on plants. Hellebore has its chief 

 advantage in being much less poisonous than the arsenical prepa- 

 rations. It does not injure the leaves of plants and is less dangerous 

 to crops that are to be used directly as human food. 



Principles of Fighting Biting Insects. — There are a number of 

 important principles to be borne in mind in fighting biting insects. 

 First, make sure that the insects are of the biting kind. By 

 observing their work, see what damage is being done. If the surface 

 of the leaves is being taken by them, or if the leaves are being eaten 

 in any way, or if the fruit is bitten, then you know that the insects 

 are of this type. Poison sprays should be applied as soon as the 

 work of the biting insects begins. Success depends upon getting 

 them before they do much damage (Fig. 218). 



The spraying material must be strong enough to poison the 

 insects, and should be made attractive enough so that they will 

 eat it. Usually the leaves will be attraction enough, but some 

 sweetening is sometimes used. 



Danger to foliage must be avoided. In nearly all cases this is 

 possible by the use of lime added to the water sprays, or by using 

 Bordeaux mixture containing plenty of lime. 



Insects which are soon to become imbedded in fruits must be 

 poisoned at the very moment they are entering the fruits; for 

 example, with apple worms and plum curculio insects this princi- 

 ple applies. It is necessary that the poison be on the surface ready 

 for the insect to get his first mouthful, otherwise spraying would 

 be too late. 



To Fight Sucking Insects. — By sucking insects we mean those 

 which take their food in the form of juices through sucking tubes 

 which they insert below the surface of the leaves, fruit or stems. 



