66 SOME INSECTS INJURIOUS TO TRUCK CROPS. 
Experiment No. 4- — Arsenate of lead, 2 pounds to 50 gallons of 
water, was used. Kain fell as before, resulting in partial failure of 
the experiment, the poison being washed off before it had time to 
dry thoroughly. 
Experiment No. 5. — July 20, arsenate of lead was used as in experi- 
ment No. 4. Collards were also sprayed. 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 days after spraying showed that only 25 per cent of the caterpil- 
lars were killed, but July 23, a day later, few large larvae remained 
on the plants, showing that as soon as they have eaten sufficient poison 
they are killed. 
July 29, when the rows sprayed with arsenate of lead were again 
examined, they were found in much better condition than the check 
or unsprayed rows, few larvae being seen feeding, while dead ones were 
plentiful. 
Experiments Nos. 6 and 7. — July 20, a sweet-potato patch was 
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 well, as previously. The following day it rained 
hard for several hours, with the result that by July 22 the poison 
was all washed off and only a few dead larvae were found. All of 
the Paris green experiments were failures, since the rain washed the 
poison off either before it could dry or after it was well dried on the 
plant. 
Experiment No. 8. — July 23, the adhesive copper arsenite (com- 
bined with dextrine and glucose) was used at the rate of 1 pound to 
100 gallons of water and applied as in previous experiments. The 
following day no results were observed, but the foliage was not 
burned. At the end of a week no good was accomplished and the ex- 
periment was pronounced a failure. 
Experiment No. 9. — July 25, plants were again sprayed with 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 was a failure. 
Experiment No. 10. — July 25, plants were sprayed with the copper 
arsenite mixture ; 10 ounces to 50 gallons of water were applied as in 
experiment No. 8, an equal quantity of lime having been added. The 
spray did not show well on the foliage and was invisible when dry. 
It does not remain in suspension as well as Paris green and much 
residue remains in the tank. July 28, a few dead larvae were found 
