24 STATE POMOLOGICAL SOCIETY. 



tent caterpillar, the potato beetle, etc. These are very readily 

 destroyed by the application of some form of arsenic, as Paris 

 green, to the parts which will be eaten. 



Another class of insects, e. g., the plant lice and some of the 

 scale insects, obtain their food by sucking the juices of the plant 

 and, therefore, are not affected by an application of poison. 

 These must be overcome by an external irritant, such as kerosene,^ 

 or an alkali like caustic soda or strong soap suds, or by some 

 material that will close the breathing pores and thus stop respi- 

 ration, e. g. pyrethrum or hellebore (in the dry form hellebore 

 acts in both ways). 



Fungi (singular, fungus) are simply low forms of plant life 

 which feed upon organic matter, either living or dead. Those 

 which grow on living tissues — parasitic fungi — are the ones with 

 which we are specially concerned. It is these which cause many 

 of the blights and rusts, and smuts and scabs and mildews of 

 various plants. Fungi are propagated by means of minute, 

 microscopic bodies, called spores, which are carried from place 

 to place by the wind and by insects, birds and other animals. 

 A spore, falling upon the surface of a leaf, or the growing tip 

 of a branch, if in the presence of moisture and the usual summer 

 temperature, germinates in a manner very similar to that of a 

 seed. If the surface of the leaf or fruit is coated with some 

 material which is destructive to the young fungus, as the spore 

 germinates, all the damage from the parasite is warded off. If, 

 on the other hand, there is even a small spot that is not coated, 

 there is opportunity for the parasite to obtain a foothold. With 

 few exceptions, after the parasite has once attacked the plant,^ 

 spraying is of little if any avail. 



WHEN TO SPRAY. 



The time of spraying will depend upon the purpose in view^ 

 but in no case should spraying be done when the plants are in 

 full bloom. Spraying at this time will often interfere with the 

 fertilization of the flowers, and consequently reduce the crop of 

 fruit, while there is much needless destruction of bees and other 

 insects which work upon the flowers. 



In general, spray early. "Delays are dangerous." Fruit 

 trees should be sprayed before the buds open, potatoes before 



