1922 ENTOMOLOGICAL SOCIETY. 21 



fested districts will have to discontinue wheat and spring rye growing for a year. 

 .and in their place sow crops that are free, or nearly so, from the insects' attack. 

 Crops that can ibe recommended for this purpose are: Oats, winter rye, barley, 

 -corn and any broad-leafed vegetable or fodder plant, including flax. 



Grains That Suffer Most. Spring wheat is the most severely infested, 

 with spring rye a close second. Durum wheat, according to Ainslie, suffers 

 almost as much as common wheat, and our own observations made over restricted 

 areas, bear out this contention. Some of our correspondents in North Dakota, 

 however, claim a much greater immunity for durum than other wheats, but it is 

 necessary to know more about the conditions under Which it was grown before 

 we can reach definite conclusions as to its utility. iSpeltz also is badly infested 



As a general rule, it seems that quickly maturing crops are \ safer to sow 

 than late ones, and in this respect it might be worth while testing one or 

 more of the new early wheats. A winter wheat hardy enough to stand our 

 climate would probably prove an ideal factor in overcoming the sawfly depreda- 

 tions. 



The Destruction of Grasses. It was C. N. Ainslie who first questioned 

 ."the utility of destroying infested grasses owing to the fact that these harboured 

 large numbers of parasites. The problem is a moot one and requires careful 

 study. In 1921, we found Brome grass (B. enermis) invested with sawfly to the 

 extent of 70 per cent but from these infested stems not more than 5 per cent 

 of the larva3 reached maturity and of those that cut and plugged the stems, 

 not more than 6 per cent survived. In other words there was a death rate of 

 04 per cent very largely through parasites. To cut the grass in July for the 

 purpose of destroying the larva? would, under such circumstances, he jof no 

 practical value, and might do considerable harm. Judging from our work of 

 1921 other grasses mature a larger number of sawflies than does brome. A field 

 •of Agropyron tenerwm, for instance, showed a parasitism of about 35 per cent in a 

 total infestation of 72 per cent, and practically the same death rate was recorded 

 in Agropyron richardsonii. In these there would seem to be an overflow of adults 

 sufficient to infest nearby crops, leaving their enemies to attend to those that 

 remained to breed in the grass; whereas if these grasses were cut early in July 

 all the sawfly larva? would be killed while the parasites which had not yet 

 oviposited might be induced to fly to infest hosts in the growing grain. 



From the evidence so far obtained we believe Brome grass can safely be 

 left to rear sawfly parasites, but that other grasses should be cut before the 

 middle of July to kill the sawfly larva? infesting them. 



Hardiness of Larvae. The larva? are capable of great endurance, and 

 for that reason we have been unable to discover any practical method of destroy- 

 ing them in the fall. Immersing the infested stubs in water for three days merely 

 produced a torpor which passed off after a few houirs. Exposing the stubs to 

 all- the vicissitudes of autumn, winter and spring on top of the ground was also 

 of no avail. Burning the stubble is likewise abortive. 



In conclusion, it is my pleasure to acknowledge the help I have received 

 from Mr. C. N". Ainslie, both personally and through his publication. I am 

 indebted to Mr. W. E. Walton for his kindness in arranging for the determination 

 •of parasites, and to Mr. M. P. Tullis of the Department of Agriculture, Begina, 

 for information concerning the sawfly outbreak in 'Saskatchewan. Finally, I have 

 "to acknowledge the assistance of my fellow worker, Mr. P. X. Yroom, who has 

 been with me during the last two summers. 



