SMITHSONIAN INSTITUTION LIBRARIES 



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ma3' be that atmospheric conditions have had something to do with 

 exemption in the cases which have come under notice. 



Rotation of crops is advisable, and it is unwise to plant peas in suc- 

 cessive years in the same portion of a farm or garden, or in the vicinity 

 of fields of red or crimson clover, or other leguminous plants, such as 

 vetch, which are likely to harbor this species. 



As has been said, this insect passes the winter .on the plants 

 mentioned, because peas are not available, and it might be possible 

 to use small plats of some one of them as trap crops. Crimson clover 

 would probably be best because of its conspicuousness and the early 

 start that it gets in the spring. On the trap plants the lice could be 

 killed l)y hand methods, such as brushing from the plants into pans 

 and thus large numl)ers of the insects could be killed early in the sea- 

 son before they had'opportunity to spread to peas. 



In Delaware it has been shown that the practice of keeping the 

 land well fertilized and frequently cultivated enables the peas, in 

 spite of lice attack, to produce better crop>s than would otherwise be 

 made. 



The suhjert of alternate host plants is an important one, since 

 the pea, being an annual, is not available as food for this plant-louse 

 during winter, and it is desirable to ascertain all of its host plants, 

 and more especdall}^ weeds, as some one or more of these may be 

 factors of importance in the life economy of the species. It might 

 be necessary in the future, should the depredations of this insect 

 continue as during the past two years, to limit the growing of clover 

 and other legumes, as well as other alternate host plants, if such be 

 found, in the vicinity of pea fields. If all of the principal alternate 

 plants could be discovered this might furnish a solution of the problem 

 of how to deal with this insect. 



F, H. Chittenden, 



Approved : Assistant Entomologist. 



J. H. Bkigham, 



Acting Secretarn of AijricHltare. 



Washington, D. C, M((ij 23, 1901. 



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