CACTUS SOLUTION AS AN" ADHESIVE. 5 



The cucumber beetle appeared, as will be seen from the foregoing 

 table, to succumb more readily to the Paris-green spray than to any 

 one of the former sprays of zinc arsenite. In the field experiments 

 there was not much difference, though the zinc arsenite gave more 

 favorable results in that it lasted longer. The dews in the lower Eio 

 Grande Valley are usually heavy ones, which would naturally reduce 

 the effectiveness of the Paris-green application. But, as already 

 shown, in the pot experiment the results appeared much more quickly 

 than with the other sprays. 



UNSATISFACTORY RESULTS WITH LEAD ARSENATE. 



Since the experiments with cactus as an adhesive and a spreader 

 for zinc arsenite and for Paris green and lime had resulted so favor- 

 ably, not only in increasing the adhesiveness of the spray, but also in 

 the destruction of the beetle, it was decided to try it in combination 

 with lead arsenate. The cactus was placed in a barrel of water about 

 12 hours before the arsenate of lead was added. A few minutes after 

 adding the lead arsenate the formation of a precipitate was observed. 

 In an hour's time a cottony scum had formed on the surface and 

 appeared fairly well distributed throughout the mixture. In the 

 meantime spraying had been going on, but with little success, as this 

 semiliquid matter clogged the nozzles. In about two hours' time the 

 precipitation was more complete and the solution was discarded, since 

 its consistency rendered it useless for spraying purposes. Alkalinity 

 of the water was at first suspected, and rain water was substituted, 

 but with the same results, so that no further attempt was made to use 

 the cactus with lead arsenate. The lead arsenate employed was air- 

 dried, having been formerly paste which had dried out in an open 

 keg ; but no doubt even with fresh arsenate of lead the same precipi- 

 tation would have taken place, as the air-dried arsenical had been 

 used successfully without the cactus and had remained in solution, 

 although it did not adhere well. 



In experiment No. 14 (Table V) arsenate of lead was employed at 

 the rate of 3 pounds to 50 gallons of water. As the potted plant was 

 quite small, there was not sufficient foliage to support a great number 

 of beetles, and on April 4, at 6 p. m., six belted cucumber beetles were 

 placed on the plant. 



Table V. — Experiment No. i-'/.— Cactus as an adhesive with arsenate of lead.. 



Brownsville, Tex., 1913. 



Date. 



Apr. 6. 

 Apr. 7. 

 Apr. S. 

 Apr. 9 . 

 Apr. 11 



Beetles 

 present. 



Living. 



Dead. 



Feeding. 



Not feed- 

 ing. 



