26 



BULLETIN 842, U. S. DEPARTMENT OF AGRICULTURE. 



In Table IV also are given the data secured by treating soaked 

 galls with mercuric chlorid, copper sulphate, and sulphuric acid. 

 As can be seen, these results are comparable to those obtained with 

 formaldehyde, namely, that the nematode is strikingly resistant to 

 the chemicals and that treatments with these chemicals which are 

 not injurious to the wheat fail to kill the larva?. 



LARV.3E OUTSIDE OF THE GALLS. 



The method of treating unprotected larva 1 outside of the galls 

 consisted in placing the actively moving nematodes, usually those 

 removed from a single water-soaked gall, in the solution in a Syra- 

 cuse watch glass. From the time the larvae were put into the dish 

 they were kept under continual microscopical observation for sev- 

 eral hours, or a day, until after all signs of life had disappeared or 

 until the treatment was discontinued. At the end of the experiment 

 the percentage of larvae living was noted, and this, with other data, 

 is given in Table V. 



Table V. 



-Effect of various chemicals on unprotected larvae of the wheat 

 nematode outside of galls. 



Chemical. 



Treatment. 



Strength. 



Exposure. 



Date. 



Number 

 of lots of 

 larva?. 



Larva? 



living 



(per 



cent). 



Formaldehyde . 



Mercuric chlorid . 



Copper sulphate. 



Sulphuric acid. 



Hours. 



Check. 



1: 240 



1: 120 



1: 100 



1: 80 



1:50 



1: 25 



1: 1,000... 



2: 1,000... 



4: 1,000... 

 10:1,000... 



5 per cent . 



10 per cent 



15 per cent 

 | per cent . 

 1 per cent . 



11 per cent 



Tap water 



Days. 



Minutes. 

 55 



5 

 15 



5 

 36 

 45 

 32 

 25 

 46 

 50 

 14 

 17 

 25 

 35 

 27 

 55 





 30 





 30 

 35 





 15 

 15 





 15 

 45 





 20 







5 

 25 



5 

 50 



May 31 

 June 1 

 May 31 

 June 1 

 May 14 

 May 17 

 May 31 

 June 1 

 May 14 

 May 17 

 May 14 

 May 17 

 May 31 

 June 1 

 May 31 

 June 1 

 May 31 

 June 1 



...do.... 

 May 16 

 June 1 

 May 17 

 May 16 

 June 1 

 May 17 

 May 10 

 June 1 

 May 17 



...do... 

 June 1 

 May 17 

 June 1 

 May 17 

 June 1 



/May 14 

 \May 31 



A study of Table V shows that the larvse are extremely resistant 

 to the toxic action of the chemicals, living 4 hours and 55 minutes 



