2l6 MAINE AGRICULTURAL EXPERIMENT STATION. I906. 



true sexes of this species do not appear upon the potato. It 

 is not yet known what plant serves for the alternate host. 



Aphis sp. This present season in some parts of Aroostook, 

 conspicuously at Caribou and vicinity, a second species of plant 

 louse, an undetermined and probably a new species belonging to 

 the genus Aphis, has heavily infested certain fields. They were 

 beginning to appear upon the vines about the middle of July 

 and they had not all taken flight by the middle of September. 

 At the later date colonies of pupae could be found here and there 

 at Caribou, clustered thick enough on stalk tip and new growth 

 to hide the stalk. The bodies of these pupae shaded from pink 

 to salmon and from green to brown. They seem invariably to 

 feed head down. 



The presence of plant lice to such an extent upon potato vines 

 raises several perplexing problems. If a fairly uniform attack 

 could be reckoned on each year, the cost, benefit and practibility 

 of emulsion sprays on the infested fields would be well worth 

 testing. Plant louse attacks, however, are likely to be irratic, 

 influenced by climatic conditions and by decrease and increase 

 of parasites and predaceous insects. As yet it seems to be an 

 open question as to whether it is most practical to attempt to 

 combat the aphids in the potato field by artificial means, or 

 leave them to fluctuate according to natural influences. At any 

 rate their presence is to be regretted. Even a light attack which 

 would not preceptibly weaken the plant, probably renders it 

 more susceptible to fungus diseases than it would normally be. 

 For the past 3 years the aphid attacks on potato have been wide- 

 spread. Dr. James Fletcher, Central Experimental Farms, 

 Canada, writes from Ottawa, September, 1906, " The aphis has 

 been extremely abundant on our potatoes all through this part 

 of Canada this year." It also troubled Canadian fields in 1904. 



Alder Blight and Attendant Insects. 

 A conspicuous illustration of the natural fluctuations of insect 

 conditions is given by Pemphigus tesselata in the vicinity of 

 Orono. This species, a large dark bodied plant louse infesting 

 the trunks and branches of alder {Alnus incana), is often mis- 

 taken for fungus on account of the snow-white flocculent matter 

 with which it is covered. For several seasons the alder clumps 

 here as in many other parts of the State have been white 

 stemmed with this woolly plant louse, and early in September 

 the air has been alive with the winged forms. 



