POTATO PLANT LOUSE. 247 



observation. After the insectary material was found to accept 

 pea vines for colonization, the fact that it is the custom in 

 Aroostook County to plant peas with oats as a part of the crop 

 rotation including the potato was remembered. These pea vines 

 are, of course, sheltered by the oats and as they are cut merely 

 for fodder a summer infestation of aphids would, unless espe- 

 cial search was made, pass undetected. 



In the vicinity of Houlton, September n-September 16, 1907, 

 search on the peas growing with oats was made and both 

 winged and wingless forms of Nectarophora sp. apparently like 

 N. solanifolii were found. Like the Nectarophora upon potato, 

 shepherd's purse, and buckwheat, the species upon peas was 

 too badly attacked by fungus to render much work with it 

 possible. 



In view of the fact, however, that the species upon the potato 

 will feed and multiply readily upon pea vines (see insectary 

 notes) it might be advisable, if the trouble continues to be 

 seriously prevalent, to omit the peas from the rotation scheme. 

 For potatoes upon numerous 20 to 60-acre fields one year and 

 peas over the same area the next would seem to offer an 

 unbroken opportunity for the growth of the summer genera- 

 tions of this destructive plant louse. This suggestion does not 

 touch the question of the winter host, because it would be 

 upon these vines as upon the potato that the summer genera- 

 tions would occur, and even if eggs were deposited upon the 

 pea, as it is harvested with the oat crop it could not serve as a 

 dangerous winter host. 



Summary as to Remedial Measures. 



1. The standard remedies for plant lice, emulsion sprays, 

 do not seem practicable for the large potato crop of Maine. 



2. No other direct remedy seems to be more available. 



3. It is apparently futile to attempt to combat this species in 

 Maine through the medium of the winter host. 



4. Clean culture may legitimately be classed among the 

 available preventive measures with this pest as with most crop 

 pests. Since it has been ascertained that N. solanifolii passes 

 the winter in the egg stage and that the eggs are attached to the 

 leaves of its host, shepherd's purse and possibly various other 



