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of plantlice last season was comparable only with the out- 

 breaks of 1897 and 1903, years distinguished by the super- 

 abundance of these pests. Observation and weather records 

 show a distinct correlation between a low, unseasonable 

 temperature and the multiplication of plantlice. The past 

 summer was remarkably cool and backward, a marked 

 change for the better occurring June 21. That the earlier 

 cool weather was favorable to the plantlice was evidenced 

 by the hosts appearing upon the leaves of many trees. The 

 reason is probably found in the fact that the unusually low 

 temperature prevented the normal activity of such extreme- 

 ly beneficial natural enemies as lady beetles, flower flies, the- 

 minute 4-winged parasites and lace-wii]ged flies. Prior to 

 the occurrence of warm weather numerous lots of plantlice, 

 showing no evidence of having been materially injured by 

 natural enemies of one kind or another, were received. 

 Shortly after the rise in temperature a very different con- 

 dition of affairs obtained. Leaves injured by plantlice con- 

 tinued to come to hand, but in almost every case a few nat- 

 ural enemies had begun to reduce the numbers of the pests^ 

 or especially toward the end of the outbreak, most had been 

 destroyed and the leaves bore signs only of earlier injury. 



The lesson to be drawn from the above is that plantlice 

 outbreaks may be expected when the late spring weather 

 is unusually cool and backward, unless it is accompanied 

 by pelting rains which are undoubtedly of considerable ser- 

 vice in destroying exposed aphids. The advisability of 

 adopting direct repressive measures in specific instances, 

 must depend in a large degree upon the probability of 

 warmer weather developing soon enough so that natural en- 

 emies may check the plantlice before material -injury is 

 caused. 



Remedial measures against plantlice are well known,- 

 as a rule, though delay in their application is very general, 

 and the results secured therefore frequently unsatisfactory. 

 The experience of the last few years has shown the futility 

 of depending upon the ordinary winter or early spring ap- 

 plications of lime-sulfur washes for the destruction of aphid 

 eggs upon our fruit trees. There may be some reduction, 

 but the percentage killed in this manner is so small as to be 

 negligible. The practicability of destroying these minute 

 enemies of our plants by thorough applications of contact 

 insecti(*des, such as tobacco preparations, whale oil soap 



