CHAPTER XT 



IXSECTICIDES AXD FUXGICIDES* 



Ammoniacal copper carbonate. — Tliis is not as good for gen- 

 eral purposes as Bordeaux mixture. It is used instead of 

 Bordeaux wlien it is desirable to avoid the spotting of leaves or 

 ripening fruit. It is prepared as follows : "Weigh out the proper 

 amount (five ounces) of copper carbonate, and use just enough 

 ammonia to dissolve it. If the ammonia is strong it should first 

 be diluted with water. Then add the proper amount of water 

 (fifty gallons). 



Arsenate of lead. — Arsenate of lead is one of the most valued 

 of the arsenical insecticides. It has in many cases entirely dis- 

 placed Paris green with orchardists, and there are at least three 

 good reasons for it : 



1. The arsenate of lead has great adhesive qualities. It will 

 not wash off, even in heavy showers of rain. Some of our experi- 

 ments here at the Station showed the presence of this arsenate 

 on the leaf, in sufficient quantity to kill insects, ten weeks after 

 spraying. 



2. It can be used in any strength without burning the foliage 

 of the plant sprayed. 



3. It has some fungicidal properties that are increased when 

 added to lime sulphur. 



Arsenate of lead can be made at home or bought in paste form 

 on the market. Ordinarily it w^ill be easier to buy the prepared 

 material. 



Formula for TTome-iiade Preparation: 



22 ozs. acetate of lead (sugar of lead) dissolved in 2 galldn.s 

 of warm water in a wooden pail. 

 S ozs. arsenate of soda dissolved in 1 gallon warm Avater in 

 another wooden pail. 



These two solutions, poured together, make a sufficient quan- 

 tity of poison for fifty gallons of spray. 



Three pounds of the commercial paste are recommended for 

 fifty gallons of sjDray. 



Arsenite of lime. — This is essentially a home-made prepara- 



' By permission of Minnesota Experiment Station. 



187 



