256 ANXUAL REPORTS OF DEPARTMENT OF AGRICULTUEE. 



cheaper. Experiments in northern Maine indicate that Pickering 

 sprays exert the same stimulating action on potato plants and in- 

 crease in yield to the same extent as standard Bordeaux sprays. A 

 barium copper spray was prepared which possessed some very desir- 

 able properties as a fungicide and gave satisfactory results on po- 

 tatoes. A public patent covering the preparation and use of this 

 product has been obtained. 



As a result of investigations of the problems involved in spraying 

 potatoes and other plants with Pickering and other copper sprays, 

 papers were prepared during the year on "Absorption of copper 

 from the soil by potato plants" and on "The influence of copper 

 sprays on the yield and composition of the tuber of the Irish 

 potato." 



Chemical and physical studies of insecticides and investigations 

 on the physiological effect on insects of arsenical insecticides and of 

 the materials entering into their composition have been carried on 

 for the past four years in cooperation with the Bureau of En- 

 tomology. Some of these results will soon appear in bulletin fom^ 

 under the title "Arsenicals: Chemical, physical, and insecticidal 

 properties." 



Investigations in cooperation with the Bureau of Entomology 

 have been carried on in Texas for the purpose of devising methods 

 for the control of screw worm flies and related species which in- 

 fest live stock, particularly cattle. Several attractants have been 

 discovered, of which dried eggs seem to be the most promising 

 These when used in connection with traps have been found to be of 

 great value in reducing the number of flies. Several promising repel- 

 lents have also been found and are being further tested. 



An investigation was made to determine the quantity of poisonous 

 elements that may be present on sprayed fruits and vegetables by 

 reason of the excessive use of sprays, and to determine whether 

 changes can be made in the time and method of spraying by which 

 the danger from injurious metals may be eliminated. The results 

 were published in Department Bulletin No. 1027, Poisonous Metals 

 on Sprayed Fruits and Vegetables. 



Tlie results of hundreds of fumigations of various grains, vege- 

 tables, and other food products with hydrocyanic acid for the pur- 

 pose of destroying insect pests infesting them are embodied in a 

 manuscript prepared under the title " The absorption of hydro- 

 cyanic acid by fumigated food products." 



Foliage injury by lead arsenate and other insecticides was studied 

 to determine the action of various impurities in lead arsenate on 

 foliage, and the action of natural water containing various salts 

 on lead arsenate. Investigation was made of the burning proper- 

 ties of various insecticides and fungicides and an effort was made to 

 develop spray materials and mixtures effective as insecticides and 

 fungicides but producing a minimum injury to tender foliage. 



Cooperating with the Bureau of Entomology on methods for the 

 control of the Mexican bean beetle in Alabama, a number of lead 

 arsenates and other arsenicals were prepared for trial. The bean 

 plant is particularly susceptible to injury from the application of 

 arsenicals. A satisfactory poison that can be used with safety on 

 bean foliage has not yet been developed. It was found that the 



