40 



of applying each substance will be given under their re- 

 spective heads. (See Insecticides.) 



INSECTICIDES. 



The various substances, compounds and mixtures used to 

 destroy or drive away insects can be divided into three 

 groups. First, internal poisons, that kill by being eaten with 

 the natural food of the insect. Second, external remedies, 

 that kill the insect by contact, either by irritating the skin, 

 or by stopping up the breathing pores. Third, repellants, 

 including substances that keep the insects away by offensive 

 odors or by mechanical barriers. 



INTERNAL POISONS. 



Paris green is the most important insecticide of its class. 

 It kills by virtue of the arsenic that is here in chemical com- 

 bination with copper. It comes in the form of a fine pow- 

 der and can be purchased at about thirty cents per pound. 

 It can be used either as a powder to be dusted, or as a liquid 

 to be sprayed on the plants. As a powder it is to be well 

 mixed with from twenty to forty, and even eighty, times its 

 bulk of flour. Plaster of Paris or air slacked lime ; and can 

 then be evenly and thoroughly dusted on to all parts of the 

 plant by means of some kind of bellows or other powder 

 dusting machine. (See machines for applying Insecticides.) 

 One pound of Paris green to the acre is usually suflicient 

 provided the dusting be done evenly and thoroughly. Paris 

 green is sometimes used undiluted, or very slightly so (one 

 part of Paris green to three parts of flour) as is the usual 

 case with cotton, when the poison is placed in two heavy 

 sacks made of some strong cloth, as 8 oz. osnaburg, and 

 fastened to each end of a five foot pole. It is the thorough- 

 ness with which this poison is applied and not the strength 

 that secures success. As a liquid Paris green is to be mixed 

 with water in the proportion of one pound poison to from 150 

 to 200 gallons water. Paris green does not dissolve in 

 water, and since it is very heavy and tends to settle 



