16 BULLETIN 1169, U. S. DEPARTMENT OF AGRICULTURE. 
TasLe 10.—Effect of temperature and moisture on larvicidal actton of paradichloro- 
enzene, and time required to cause death, 1921. 
Per Condition of larve. 
Maxi- | cent of 
mum mois- Date eee gee ire e 
tem- | turein| joevm ov. 10. ov-17. | Daysre- | Per 
were fo lta. lu | icsclan a hued to; || cont Remarks. 
exposed vv Zz kill larvee. ; killed. 
during | larve to gas s 3 ' 1 3 
expos- | were a Ses ied al DS 
ure. |exposed a| & S| 3 ee 3 
to gas. Ala|/<|Alal< 
| 2 oR. | Percent." 119217 | Per ct 
i 69 16.75 | Nov. 4) 3) 2) 0) 2% Oj O} 5 killed in 100 | Average temperature 
13 days. 59.9° F.; larve did 
no feeding. 
II | 69 Fa Uy ba Eo CoB 3; 1} 1} 2} Of] OJ]...do.......| 100] Average temperature 
59.9° F.; larve fed a 
. | little. 
Tit 697 Leo thoes 1} 4/ 0; 4] O| OJf...do.......| 100] Average temperature 
| 60.1° F.; larve did 
Dae. 8 Dec. 16 no feeding. 
EV, 64 Ee eWec: iy oon Oy 0, | ptsc) ssp 5 killed in 100 | Average temperature 
7 days. 55.9° F.; larve did 
no feeding. 
V 64 URE ll eer (ore 3/'2).0). 2] ©} Of 5.Killed in 100 | Average temperature 
15 days. 55.2° F.; larve did 
no feeding. 
VI 64 fl lege © | PR oy oa 2.1°3)5] SO) ttle BOL BOs a dok=ce ase 100 | Average temperature 
55.2° F.; larvee did 
no feeding. 
Viilieaen see (1) Check Of BOARS y} Sa KON CASI E Le oe See) ees 4 larve fed continu. 
ously. 
1 Normal soil. 
NotTe.—Cages contained 1 ounce of paradichlorobenzene and 5 larve each. All larve were placed 6 
inches below the crystals. 
in January and February, 1922, experiments were conducted on 
soils in which different temperatures were maintained and to which 
different amounts of moisture were added at the beginning of the 
tests. The higher temperatures were maintained by keeping the 
cages indoors and the low temperatures by icing the cages in the 
insectary. The highest outdoor temperature recorded during the 
course of the experiment was 70° F. At a maximum temperature 
of 90° F. and a moisture content of from 7.6 to 27.6 per cent, all 
larve were killed in from 11 to 13 days. At a maximum tempera- 
ture of 80° F. and a moisture content of from 7.6 to 30.3 per cent, all 
larve were killed in from 11 to 13 days. Atamaximum temperature€ 
of 70° F. and a moisture content of 7.6 per cent (normal soil), 5 
larvee were killed in 11 days. At the same temperature and a mois- 
ture content of 19.8 per cent, 5 larve were killed in 17 days; and with 
moisture 27.6 per cent, 1 larva was killed in 17 days, and the remain- 
ing 4in 21 days. At amaximum of 54° F. and 6.4 per cent moisture 
(normal soil), 5 larvee were killed in 23 days. At the same tempera- 
ture and a moisture content of 20.7 per cent, 5 larve were killed in 
29 days. The larve in the untreated cage were all alive and feeding 
at the close of the experiment. Table 11 summarizes the results. 
This table shows that the lower the temperature and the higher the 
moisture content, the slower is the rate of evaporation of the para- 
dichlorobenzene, and this naturally influences the effectiveness of the 
treatment. Fairly high temperatures,? however, such as occur in Geor- 
gia during the period of treatment for the borer, even though the soil 
has a high percentage of moisture, will kill the borers within afew weeks. 
3 Average maximum daily temperature for the six-week period following the applications on October 
10, 1921, was 73° F. 
f 
