20 



BULLETIN 842, U. S. DEPARTMENT OF AGRICULTURE. 



WATEB-SOAKED GALLS. 



A glance at the results presented in Table I, obtained from treat- 

 ing galls previously soaked, shows that the larvse are only slightly 

 affected by an immersion of as much as 15 minutes in water at 46°, 

 48°, and 50° C, respectively. They are completely killed, however, 

 when exposed for 30 minutes or more in water heated to 50° C. Al- 

 most identical results secured by the writer after subjecting another 

 parasitic nematode, Heterodera radicicola, to the same treatments 

 suggest that other plant-attacking nematodes may respond similarly. 



Table I. — Effect of hot-water treatment on larvce of the wheat nematode in- 

 closed in wet galls. 



Lot. 



No. 15.. 



No. 14.. 

 No. 13a. 

 No. 13.. 

 No. 12.. 

 No. 11a. 

 No. 9... 

 No. 8... 

 Iso. 17.. 

 No. IS.. 

 No. 2... 

 No. 19.. 

 No. 23.. 

 No. 24.. 

 No. 25.. 

 No. 26.. 

 No. 11.. 

 No. 10. . 

 No. 20.. 

 No. 21.. 

 No. 27.. 

 No. 40.. 

 No. 44.. 

 No. 22.. 

 No. 28.. 

 No. 39.. 

 No. 45.. 

 No. 29.. 

 No. 3S.. 

 No. 1... 

 No. 30.. 

 No. 35.. 

 No. 41.. 

 No. 5... 

 No. 31.. 

 No. 36.. 

 No. 42.. 

 No. 37.. 

 No. 43.. 

 No. 34.. 

 No. 32.. 

 No. 33.. 

 No.3... 

 No.4... 

 No. 6... 

 Check.. 



Number 

 of galls, 

 each con- 

 taining an 

 average 

 of more 

 than 1,500 

 larvae 



Do. 



Hot-water treatment. 



Date, 

 1918. 



Mar. 18 



...do.... 



...do.... 



...do.... 



...do.... 



...do.... 



...do.... 



...do.... 

 Mar. 22 



...do 



Mar. 13 

 Mar. 22 

 Mar. 25 



...do 



...do 



...do 



Mar. IS 



...do 



Mar. 22 



...do 



Mai'. 25 

 Apr. 6 

 A_pr. 16 

 Mar. 22 

 Mar. 25 

 Apr. 6 

 Apr. 16 

 Mar. 25 

 Apr. 6 

 Mar. 13 

 Mar. 25 

 Apr. 6 

 Apr. 16 

 Mar. 13 

 Mar. 25 

 Apr. 6 

 Apr. 16 

 Apr. 6 

 Apr. 16 

 Apr. 4 



...do 



...do 



Mai-. 13 



...do 



...do 



...do..... 



Temper- 

 ature 

 (°C). 



Duration 



6 I Mar. 20 



C 1 ) 



Larva; active (per cent). 



Extent of 

 observa- 

 tion after 

 treatment 

 (days). 



In each gall at last 

 examination. 



Minutes. 



5 

 10 

 15 



5 

 10 

 15 



5 



10 

 15 

 20 

 20 

 25 

 30 

 35 

 40 

 45 



5 

 10 

 10 

 15 

 15 

 15 

 15 

 20 

 20 

 20 

 20 

 25 

 25 

 10 

 10 

 10 

 10 

 15 

 15 

 15 

 15 

 20 

 20 



5 

 10 

 15 



5 

 ■ 10 



Bays. 



Average- 







I 

 .49.. 













 .2 









































 95 



In 

 each 

 lot. 



SO. 83 



47.2 



58. 66 



82.5 



82.5 



73. 33 



70.83 



31.83 



75.83 



80 





 70.83 

















 44.16 

 22. .83 

 13. 37 

 14.3 

 .51 





































 .08 













 .04 









































 95 



95 



In 

 each 

 treat- 

 ment. 



SO. 83 

 47.20 

 58.66 

 82.50 

 82.50 

 73.33 

 70.83 

 31.83 

 75.83 

 40.00 



70.83 

















 44.16 



48. 1 



3.7 



}' 



.02 



i Room temperature. 



