14 BULLETIN 1169, U. S. DEPARTMENT OF AGRICULTURE. 
crystals disappeared in this cage in 16 days. The two types of soil 
showed very little difference in the rate of evaporation. It would 
appear that moisture in the soil in central Georgia soon evaporates 
and does not decrease the efficiency of the gas to any extent unless 
continuous rainy weather occurs during the period of the generation 
of the gas. Table 8 gives a summary of the results obtained on the 
rate of evaporation of the crystals. 
TABLE 8.—Rate of evaporation of paradichlorobenzene crystals in the laboratory, Fort 
Valley, Ga., 1921-22. 
One-half ounce dose to all cages on Oct. 13, 1921; one-half ounce=219 grains. ] 
Amount of evaporation, in grains (losses be- 
tween succeeding dates). Num- 
| ber of 
Ge B= a ee ee ee 
Depth of | days re~- 
crystals | “Amountof | soit 1921 1922 anotal , | quired 
Betie" added Och, ds.). She a te eee ee ae 
soil. : I a : E 5 - | orated. | orate 
Gigli laislSiesisj«|s]s crys- 
2 Bay |B LI (kt = lin) Spee] | So lays 7 | 2 (40 |e i 
olo;/o}]oao/8/8 
616lazizlalalsls§ialsia 
Surface...| Normal soil...| S rte Gey 122, i SBy io ese eas leece PS Sea a Ee Oct. 30 16. 
| oam. 
4inehes..-:|.. 22. “CLC ees ee Re G60. 2 17 |. 18))\ (8°45? Jttg 48 17 .| Feb. 18 128. 
6inches...| uneere 0 V0) elie, See Sart dos. 16) SLO Sia Seal 27 AVG OE le taletes Gores 128 
4inches...| 180 cubic cen- dots 7 183) 4s bea e230 ag SOU < Scilly Sees Feb. 4 114 
timeters of 
water added.a 
Ginches...|..<.. Gowes- 7s 3 do: .-F- 8 | 12 | 12 | 28 | 59 | 39 oT Fe 93 hel yee I | WR ro (a yee 114 
4inches...| Saturated @. ‘dott 0} 31]18 | 64 | 61 | 30 2 A aia ae ml plan Jan. 12 91 
6inches...|..... 0:6 52 052| 235 0: 4.4: 0!) Doe) ZZ 66 [44 Sl 2S: sete ys Bie eee Jan. 5] . 84 
4 inches...| Normal soil. ..| Red clay} 10 | 15 | 13 | 63 | 49 | 35 |....] 34 |....[...1.... Jan. 12 gl 
Grichesss|. 3 [00s FAS 3 dott és? 8 TE} TO WeB9e] 49 HN) AP) aD [ch sh 22 Le wep sis 128 
4inches...| 180 cubic cen- |...do..... OO) ARS ah At U0 i: Hy PR el fet: aa [pepe IE Jan. 12 91 
timeters of | 
water added. 
Ginchess. doses. -. = yeasts 0) 14) 14 |-S8 180" 33 .|... 21536 [oo Sa" 10 | Heb; 925 135 
4inches...| Saturated a....|...do..... Oue2Hl SAWSZHSS aL (27 eee Eat. an. 115 84 
Ginehes-.<|....- Gordes 252—- Sexi ee 0 | 18 | 21 | 42 | 58 | 45 cee BS oclisetelose last Jan. 12 91 
a This water added to soil in flowerpots 10 inches high and 6 inches wide. These pots were used as soil 
containers for all of the above paradichlorobenzene evaporation tests. 
MORTALITY OF PEACH-BORER LARVZ EXPOSED TO PARADICHLOROBENZENE. 
Peach-borer larve were collected in the field and brought to the 
insectary to determine the effect of paradichlorobenzene on them. 
All larvee were placed on peach bark and set in the soil from 3 to 12 
inches below the crystals. From one-half ounce to 2 ounces of para- 
dichlorobenzene was used in the different cages that contained the 
larve. Each cage had five larve, and all were killed in three weeks’ 
time. The larve that were placed in normal soil with from one-half 
ounce to 2 ounces of paradichlorobenzene per cage were all killed 
within two weeks. The generation of gas was retarded somewhat 
in the cages where a large amount of moisture had been added, but 
the larve in these cages did not live more than a week longer than 
those placed in normal soil. One cage had no crystals in it, and all 
the larvee in this cage were alive and feeding at the close of the experi- 
ment. The standard 1l-ounce doses killed all larve in two weeks, 
although the larve did a little feeding before death. The odor of 
gas was noticeable in one week at the bottom of all cages except 
those to which 360 and 540 cubic centimeters of water had been 
added, in which it did not become strong until the end of the second 
week. Table 9 summarizes the results obtained and shows that the 
paradichlorobenzene is effective in killing the larve as far down as 
1 foot, under normal conditions and standard dosage. 
