125 



liquid Bordeaux mixture, as well as the relative cost and efficiency 

 of spraying and dusting. Bordeaux mixture did not prove in any 

 M^ay superior to the lime-sulphur wash used in the test orchard 

 for the last ten years. Both dusting and spraying proved very 

 satisfactory ; dusting is certainly the more expensive method, but 

 it IS also quicker in apphcation. The most economical 'dust 

 consisted of 15 lb. sulphur, 5 lb. calcium arsenate and 80 lb. 

 hydrated lime, calcium arsenate being cheaper than lead arsenate. 

 Dust Bordeaux was used with satisfactory results, the formula being 

 46J lb. dry Bordeaux, as commercially prepared, with an equal 

 quantity of hydrated hme and 7J lb. calcium arsenate. 



ToTHiLL (J. D.). Insect Outbreaks and their Causes.— 50th Ann. Kept 

 Ent. Soc. Ontario, 1919, Toronto, 1920, pp. 31-33 TReceived 

 8th January 1921.] ' 



An insect outbreak is generally due to the relaxing of some pressure 

 of its environment that has previously held the species in equilibrium. 

 Several well-known epidemics are mentioned in illustration of this' 

 There is in New Brunswick at present an incipient outbreak of the 

 fall webworm [Hyphantria cunca], and the causes that have con- 

 tributed to this are discussed. In 1912 this moth had been fairly 

 numerous for a decade or more, finding an abundance of its favourite 

 food (alder) along the streams and waterways. The various factors 

 constituting environmental pressure consisted of parasites of the 

 various stages and of birds, particularly the red-eyed vireo. As a 

 result of this pressure it is computed thatthe average number of moths 

 yielded by each egg-mass (consisting of an average of 260 eggs) would 

 be less than two, and this decrease in numbers continued steadily 

 until 1916, when the insect became almost extinct in the Province 

 its parasites dying out with it. Then a flight of moths was blo\\Ti 

 across the Bay of Fundy, and heavily infested a considerable area 

 along the coast. Birds have not been sufficient to keep this infesta- 

 tion in check, and parasites are not likely to be present until the 

 present outbreak extends to the territory in which they now occur. 



It is also pointed out that civilisation is responsible for many 

 notorious outbreaks. In New Brunswick large tracts of forest lands 

 have been planted with pure stands of poplar in place of the old 

 mixed growth, thus encouraging the forest tent caterpillar [Malacosoma 

 disstria], while similar areas of balsam fir provide abundant material 

 for an outbreak of spruce budworm [Tortrix fimiiferana]. In these 

 cases, the restraining factor that has previously held the numbers 

 in check was the limited supply of food. 



Ross (W. A.) & Robinson (W.). Further Notes on the Control of 

 Pear Psylla.— 5^^A Ann. Kept. Ent. Soc. Ontario, 1919, Toronto 

 1920, pp. 33-38. [Received 8th January 1921."] 



Experiments are recorded with various ovicides for pear psylla 

 [Psylla pyricola] at different stages of incubation. Lime-sulphur 



1 : 7 proved most effective, destroying all eggs, but affecting newly- 

 laid ones more readily than those about to hatch. The addition of 



2 lb. starch to 40 gals, of weaker lime-sulphur spravs increased their 

 T?i ?K ^" ^^^^"^ soluble suphur, 10 lb. hydrated lime was added to 

 12^ lb. sulphur in 40 gals, of water to prevent injury to the bursting 



