296 



well. The next acre was sprayed with the same poison, but whale-oil 

 soap was substituted for cactus at the rate of 3 lb. of soap to 60 U.S. 

 gallons. The sprayed plants were observed with and without a lens, 

 and it was found that the soap equalled the cactus in spreading power, 

 but was inferior in adhesiveness. The cactus spray adhered and dried 

 on the foliage better than the soap spray. This is an advantage, since 

 heavy dews will soon wash away poison having but slight adhesive 

 qualities. Copper sulphate, salicylic acid, and sodium benzoate have 

 been employed as preservatives for the cactus solution. The latter 

 kept perfectly for 4 weeks (when the experiment was discontinued) 

 when preserved with copper sulphate. Another trial was made in 

 order to test the possibility of a chemical reaction upon the addition 

 of the arsenical to the solution. Upon the addition of powdered zinc 

 arsenite at the rate of 1 lb. to 60 U.S. gals, of water, a slight chemical 

 reaction was noticed. The slight precipitate formed was not enough, 

 however, to cause any trouble when a good pressure was maintained 

 in the tank of the sprayer. No difference was observed in the effective- 

 ness of the arsenical. Lead arsenate always precipitated when added 

 to cactus solution, but if the latter is preserved as above, the 

 precipitation is so much retarded that spraying becomes possible at 

 a normal pressure with a hand pump. The above combination may 

 be used on a large scale only if a strong pressure can be maintained 

 throughout the operation. Ferrous arsenate was not altered in 

 insecticidal value when mixed with copper sulphate. Both sahcylic 

 acid and sodium benzoate were efficient preservatives of cactus solution. 

 By the use of cactus as an adhesive, not only do the arsenicals give 

 better and more lasting results, but considerable expense may be 

 saved, as the freight often costs more than the insecticide itself. Paste 

 arsenicals have been extensively used by fruit and truck growers on 

 account of their better adherence and lasting qualities. The better 

 results which have been obtained by using 1 lb. of powdered zinc 

 arsenite with cactus instead of 3 lb. of paste zinc arsenite to the same 

 amount of water show that equal results may be obtained with a 

 great reduction of freight charges. The quantity of cactus necessary 

 varies with the environment in which the plants have been growing. 

 In general, the correct proportion w411 range from 5 oz. to 1 lb. to 

 every gallon of water used in making up the spray mixture. Increased 

 adhesiveness is not very apparent at higher strengths, and difficulty 

 may be experienced in application, particularly where very fine nozzles 

 are employed. Three varieties of cactus commonly found in Texas 

 are Opuntia lindheimeri, Engelm., 0. engehnannii, Salm., and 

 0. tuna. Will. A chemical analysis of each of these three species is 

 tabulated in this paper. 



Webster (F. M.). The grasshopper problem and alfalfa culture. — 

 Z7. ^. Dejpt. Agric, Washington, D.C., Farmers' Bull, no. 637, 

 25th January 1915, 10 pp., 8 figs. 



Lucerne, to a greater extent than other crops, provides the two 

 conditions which grasshoppers require in order to breed freely and in 

 destructive numbers, i.e., an midisturbed soil for the protection of 

 the eggs, and an early food supply for the young in spring. From 

 the beginning of lucerne culture, the farmer, especially in the West, 



