12 BULLETIN 278, TJ. S. DEPAETMENT OF AGRICULTURE. 



water. Arsenate of calcium, homemade (2), was prepared from 

 sodium arsenate and calcium chlorid, the method of procedure 

 being the same as for arsenate of calcium, homemade (1), and was 

 used at the same strength. 



Lead chromate, commercial, was used at the rate of 8 pounds to 

 50 gallons. Lead chromate, homemade, was prepared by dissolving 

 2 ounces of lead nitrate in one lot of water and 1 ounce of potassium 

 bichromate in another lot of water. The two solutions were then 

 mixed, and a dense yellow precipitate of insoluble lead chromate was 

 formed. The amount of lead chromate formed is 2 ounces, and the 

 strengths at which the material was used in these experiments were 

 based on the amount of lead chromate formed. 



H. Maxwell-Lefroy and R. S. Finlow state the following in regard 

 to the use of the above form of homemade lead chromate as an insecti- 

 cide : 1 



During this year we have applied this compound to a great variety of crops. We 

 have sprayed them till every leaf was yellow. The poison has remained on for over 

 three weeks, thickly on the leaves, which were uninjured. Sprayed on to crops at- 

 tacked hy caterpillars, the caterpillars are killed, and the results obtained have beer, 

 excellent. We have used this at 1 pound in 32 gallons. At this strength it is entirely 

 safe, poisons caterpillars, and acts as a very powerful deterrent. * * * Lead 

 chromate has not the poisoning effect of Paris green, for instance, which can be applied 

 at 1 pound in 200 gallons, but it has a poisoning effect comparable with tbat of lead 

 arsenate, and is, in our experience, a perfect substitute. 



As a result of this success with the use of this preparation as an 

 insecticide in India, thorough tests were made with it in experiments 

 conducted during the season of 1913. 



Experiment VI. 



ARSENATE OF LEAD VERSUS ARSENATE OP CALCIUM AGAINST LARV.E OP THE TENT 



CATERPILLAR. 



In this experiment arsenate of lead paste and the different forms 

 of arsenate of calcium were tested in comparison against newly 

 hatched larvae of the tent caterpillar. The results of this test are 

 shown in Table VI. 



Arsenate of lead alone killed the 50 larvae in each of the two lots 

 in 5 days, with 0.04 square inch of foliage consumed. Combined 

 with lime-sulphur it required 2 days longer to kill, but only 0.01 

 square inch of foliage was consumed. 



Arsenate of calcium, homemade (1), prepared from sodium arse- 

 nate and calcium acetate, killed the larvas in 5 to 7 days, with 0.05 

 and 0.06 square inch of foliage consumed when used alone, and in 5 

 days when combined with lime-sulphur, with 0.02 square inch of 

 foliage consumed. Arsenate of calcium, homemade (2), gave prac- 

 tically the same results. • 



1 Maxwcll-Lcfroy, n.,and Finlow, Tl. S. Inquiry Into the insectlcidal action of some mineral and 

 other compounds on caterpillars. In Memoirs Dcpt. Agr. India, Ent. Scr., v. 4, no. 5, p. 209-327, 1913. 



