BULLETIN 1205, U. S. DEPARTMENT OF AGRICULTURE. 
DUSTING IN 1921. 
On August 12, which was about four weeks after the fruit had been 
harvested, plats 1 and 2 received the first post-season dust of 90 per 
cent hydrated lime and 10 per cent powdered arsenate of lead. One 
hundred and three pounds of dust were used on the 504 trees in 
plat 1, and the actual time required to make the application, exclusive 
of filling the hopper, was 1 hour and 9 minutes. Ninety pounds of 
dust were used on the 504 trees in plat 2, and 1 hour and 25 minutes 
were spent in making the application. More time was spent in 
dusting plat 2 than would normally be required, because the driver 
was unfamiliar with the plat. Tne weather conditions during the 
day were excellent for dusting, and no rain fell during the two weeks 
following. 
On August 24, plat 1 received the second post-season dust of the 
same formula as that applied two weeks before. This time 106 
pounds of dust were used on the 504 trees, and 1 hour and 5 minutes 
were required to make the application. The day was clear, with a 
light wind from the west. Ten hours after dusting a light shower 
fell, followed by a heavier one 7 hours later. Observations the next 
day showed that a considerable amount of dust had been washed off. 
The dust applications were made with a large dusting machine 
driven by a 3|-horsepower engine, all mounted on a light wagon (PL 
II, fig. 1). It was found that effective post-harvest dusting could 
be done with about one-fifth of a pound of dust per tree. The time 
required to dust 1,000 trees after harvest was found to be about 2) 
hours. Figuring the lime cost at 1 cent a pound, the powdered 
arsenate of lead at 24 cents a pound, a pair of mules at 30 cents an 
hour, and two men at 15 cents an hour each, the total cost per 
thousand trees for this post-harvest dusting was around $8.10, or 
0.81 cent per tree per application. 
JARRING AFTER DUSTING. 
In order to measure the effectiveness of post-harvest dusting, the 
record trees in each plat used to determine the degree of the infes- 
tation before dusting were jarred every other morning for several 
weeks after the applications were made. Table 2 gives the number 
of beetles collected from the record trees in each plat between the 
first and second applications of dust. 
Table 2. — Number of curculios collected between first and second dustings, 1921. 
Aug. 13. 
Aug. 15. 
Aug. K>. 
Aug. 17. 
Aug. 18. 
Aug. 19. 
Aug. 20. 
Plat. 
Betitte*. 
252 
229 
Beetles. 
265 
"348 ' 
*37i 
Beetles. 
552 
Date. 
Aug. 22. 
Aug. 23. 
Aug. 24. 
Total 
Average per tree. 
Plat. 
Beetles. 
1,015 
4.06 
Beetles. 
311 
1,573 
6.29 
Beetles. 
590 
2,725 
10.90 
The five collections made from the 50 record trees in each plat from 
August 13 to August 24, therefore, showed the presence of an average 
