22 



SCIENTIFIC AGRICULTURE 



September. 1921 



been blowu across the Prairies for hundreds 

 of miles and had left their enemies behind. 

 The most important parasite — a two 

 winged fly — was collected near Vancou- 

 ver and colonized at Sylvan Lake and it is 

 expected that this will assist in reestab- 

 lishing the natural balance of things. It is 

 too early as yet to know how much good 

 will accrue from this project but there will 

 of necessity be some improvement in tlie 

 situation. 



Tlie Fall Webworm, Forest Tent Cater- 

 I)illar and Spruce Bud worm have been 

 studied intensively for several years and 

 throughout the Dominion and these studies 

 have served as a background for develop- 

 ing the various practical projects. They 

 will serve also as foundational studies upon 

 which to base future practical projects that 

 may be undertaken. They have served to 

 emphasize the wastefulness of an agricul- 

 ture that is carried on without the aid of 

 natural enemies of insect pests. They have 



shown that there are probabilities of sav- 

 ing millions of dollars by using intelli- 

 gently all tlie natural means at our disposal 

 for the control of agricultural pests. 



There are two objectives for natural con- 

 trol work in Canada. One is to regulate 

 within the Dominion the distribution of the 

 natural enemies of injurious insects. The 

 other — and more important — is system- 

 atically to introduce all the parasites of 

 our imported pests that are not already 

 here. Our agricultural pests are, for the 

 most part, imported from foreign lands 

 and many of the para.sites have been left 

 behind. These two objectives cannot be at- 

 tained at once or even in a decade. They 

 are of practical attainment, however, and 

 within our own generation. With the ob- 

 jectives reached, there should be millions 

 of dollars saved annually to our agricul- 

 ture and the investment will yield interest 

 for all generations to come. 



The Apple Sucker sfhSeTgtr) in Nova Scotia 



By W. H. BRITTAIN, 

 Provincial Entomologist. 



Present Distribution. 



This injurious insect was first found in 

 Nova Scotia in 1919, though doubtless in- 

 troduced some years before on nursery 

 stock from Europe. It is now spread over 

 a considerable territory including parts of 

 the counties of Kings, Hants, Halifax, 

 Colchester and Cumberland. It is most 

 abundant at present in the Wolfville and 

 Coi-nwallis districts. 



The insect is a well known and much 

 dreaded enemy of the apple in Northern 

 and Central Europe, including Norway. 

 Sweden, Russia, Caucasus, Germany, Aus- 

 tria, Czecho-Slovakia, France and in Japan. 

 In some of these countries, at least, it is 

 said to be the most destructive, or one of 

 the most destructive, apple pests. For this 

 reason a short popular account of the in- 

 sect and its work may be of interest to 

 readers of this journal. 



Kinds of Plants Attacked. 



The api> 



Ic is the only iniixtrljmt food 



plant, and by some writers it is said to be 

 the only food plant, that is attacked. The 

 rowan or mountain ash {Sorhus aucuparia) 

 is also said to be attaked in Europe, while 

 in Nova Scotia it has been found to a slight 

 extent on quince and pear. The common 

 insect attacking the pear is, however, not 

 this species, but a related one, viz., the 

 pear psylla {PsylUa pyricola Foerst.) 



The Insect. 



The first indication that the grower is 

 likely to have of the presence of the pest 

 will be the dripping from the trees of small 

 drops of a whitish, sticky liquid, which, 

 in severe cases, rains down from the trees 

 at the slighte.st disturbance. On examina- 

 tion, the leaf and flower stalks will be 

 .found to be infested with small yellowish 

 or green insects, somewhat resembling 

 apliids, but flatter and more disc-like in 

 form. They are the young or nymplis of 

 the apple sucker (Psyllia mali Sehmid- 

 berger) and the sticky li(|uid is theii- fluid 



