46 PROTECTION OF PLANTS — 1923-24 



for years, and in 1915 a bulletin discussing the habits and control of these 

 two pests was published. A futther pamphlet on the former insect was distri- 

 buted in 1922 and one on the latter in 1923. In connection with studies 

 of the Western Wheat Stem-sawfly, it was noted by our officers and also by 

 provincial officers, that the larva of the sawfly does not cut the stems until 

 the plants begin to lose their sap. The early cutting of grain, therefore, was 

 recommended and this has meant savings amounting to many hundreds of 

 thousands of dollars. In 1915, and later years, Mr. Griddle made large collec- 

 tions of the adults of the grass stem maggots, (Oscinidae) which were determined 

 by Dr. J. M. Aldrich, of the United States Bureau of Entomology. IMuch 

 valuable data were thus secured on the distribution of these insects. Several 

 species of these flies were also reared from wheat, rj'e, corn and barley. 



The recent outbreak of grasshoppers in the prairie provinces, was first 

 investigated, in Manitoba, by Mr. Griddle, in 1919. The prevalent species were 

 the Roadside Grasshopper, Camnula pellucida Scudd, and the Lesser Migratory 

 Grasshopper, M elanoplus atlanis Riley. According to Mr. Griddle the outbreak 

 in Manitoba was the worst of which he had record since 1875. The total area 

 infested was more than 500,000 acres. Early in 1920, a circular entitled 

 "Locust Gontrol in the Prairie Provinces" was prepared by Mr. Griddle and 

 given wide circulation. In this year, the infestation covered a wider area 

 than that of 1919. In 1920, it was estimated that the co-operative efforts 

 of provincial and federal entomologists resulted in the saving of crops worth 

 $17,000,000. Experiments with poisoned baits consisting of sawdust of any 

 kind mixed with an equal quantity of bran were entirely successful a'nd 

 considerably reduced the cost of control. A further reduction in the cost 

 resulted from the use of salt as an attractant instead of the more expensive 

 molasses and lemons. In 1921, Mr. Geo. E. Sanders, in charge of insecticide 

 investigations, was detailed to Manitoba to assist in experimental work with 

 poisoned baits, and a temporary laboratory was established at Souris. Much 

 data regarding various attractants, etc., were obtained. This was a continua- 

 tion of similar work undertaken in Saskatchewan in 1920. During the sum- 

 mers of 1920 and 1921, j\lr. P. N. Vroom was transferred to Treesbank, 

 to assist Mr. Griddle in grasshopper investigations. 



Studies of various species of cutworms and other important field crop 

 insects have also been made by Mr. Griddle as time permitted. Live stock 

 and shade tree insects have also had his interest. During the last few 

 years one of his assistants, Mr. H. A. Robertson, has undertaken a study 

 of the mosquitoes of Manitoba. 



Few serious outbreaks of forest insects have occurred in Manitoba during 

 the last dfecade. The La'rch Sawfly, Lygaeonematus erichsonii Hartig., has increa- 

 sed in numbers and in some sections has effected important injury. In 1922, 

 Dr. Swaine studied an outbreak of the Destructive Spruce Bark-beetle, Den- 

 droctonus piceaperda Hopk., affecting white spruce, in the province. 



Parasitized cocoons of the Larch Sawfly imported from England, by the 

 late Dr. Hewitt, were distributed in larch stands in Manitoba in 1912 and 

 1913, east of Gedar Lake and near Aweme. In the spring of 1916, Mr. Griddle 

 visited the latter area and from a collection of 514 cocoons, reared 27 specimens 

 of the European parasite Mesoleius tonthredinis Morley, thus indicating that 

 the species had become established in that locality. 



With the coming into effect of the revised regulations under the Destructive 

 Insect and Pest Act, in Sept. 1923, the fumigation station at Winnipeg was 

 closed. 



