66 SOMK INSECTS IN.IT'RIOUS TO IKUCK CROPS. 



Experinieid No. Jf. — Arsenate of lead, '1 pounds to 50 gallons of 

 water, was used. Rain fell as before, resulting in partial failure of 

 the exiDeriment, the poison being washed off before it had time to 

 dr}'^ thoroughly. 



Experiment No. o. — July 20, arsenate of lead Avas used as in experi- 

 ment No. 4. Collards were also sj)rayed. Rain did not ensue for at 

 least six hours, giving the spray time to dry on well in the warm sun. 

 The following day it rained hard for several hours, but the next 

 day the spray was found to be as thick on the sweet potatoes as when 

 first put on, in spite of two partially rainy days. The poison was 

 nearly as thick on the collards. An examination of the infested plants 

 two daj'S after spraying showed that only 25 per cent of the caterpil- 

 lars were killed, but Juh'' 23, a da}^ later, few large larva; remained 

 on the plants, showing that as soon as they liaA'e eaten sufficient poison 

 they are killed. 



July 29, when the roAvs sprayed with arsenate of lead were again 

 examined, they were found in much better condition than the check 

 or unsprayed rows, few larvaj being seen feeding, while dead ones were 

 plentiful. 



Experiments Nos. 6 and 7. — July 20, a sAveet-potato patch Avas 

 sprayed with Paris green, 8 ounces to 50 gallons of water. As in the 

 case of .experiment 5, no rain fell for about six hours; therefore the 

 poison dried on Avell, as preAdously. The folloAving day it rained 

 hard for scA'eral hours, with the result that by July 22 the poison 

 was all AA ashed off and only a fcAV dead larva^ were found. All of 

 the Paris green experiments Avere failures, since the rain Avashed the 

 poison off either before it could dry or after it Avas Avell dried on the 

 plant. 



Experiment No. 8. — July 23, the adhesive copper arsenite (com- 

 l)ined with dextrine and glucose) was used at the rate of 1 pound to 

 100 gallons of Avater and applied as in previous experiments. The 

 following day no results AA^ere obserA^ed, but the foliage was not 

 burned. At the end of a week no good Avas accomplished and the ex- 

 l)eriment Avas pronounced a failure. 



Experiment No. 9. — July 25, plants Avere again sprayed Avith ar- 

 senate of lead, 2 pounds to 50 gallons of water, the conditions being 

 as in experiment No. 5. Rain at 12.45 p. m. washed off the poison, 

 consequently the spraying AAas a failure. 



Experiment No. 10. — July 25, plants were sprayed Avith the copper 

 arsenite mixture; 10 ounces to 50 gallons of water Avere applied as in 

 experiment No. 8, an equal quantity of lime having been added. The 

 spray did not shoAv Avell on the foliage and Avas invisible Avhen dry. 

 It does not remain in suspension as well as Paris green and much 

 residue remains in the tank. July 28, a fcAv dead larva^ were found 



66 — V 



