FORTY-FIRST ANNUAL CONVENTION 287 



since the vapor is heavier than air. This vapor v^^hen mixed w^ith 

 air is quite inflammable, and care should be taken not to ignite 

 it in any way; otherwise, a serious explosion may occur. One 

 pound of the liquid is usually considered sufficient to fumigate 

 JOG bushels of peas, but it is well to use somewhat more than 

 this in order to be sure of killing all the insects. 



Continuous cropping of the land to the field pea is almost 

 sure to mean a constant increase in the numbers of the pea 

 weevil. Practically the only remedy for this state of affairs is 

 to stop growing peas for several years, in which case the weevil 

 will be exterminated through lack of food. 



Attempts have been made to discover a substitute for the 

 field pea which is not subject to the attacks of this insect. Among 

 the legumes which have been tried for this purpose are the grass 

 pea and the chick-pea. The weevil does not injure either of these 

 peas, but they are not productive enough to make a profitable 

 crop for the ordinary farmer, and the market for the seed is not 

 sufficiently well established to guarantee him a dependable price. 



Another insect which occasionally does considerable damage 

 is the pea aphis, or plant louse {Aphis pisi Kalt.). It has ap- 

 peared in pea-growing sections at intervals and practically de- 

 stroyed the season's crop, but it does not stay with the crop so 

 continuously year after year as does the weevil. The aphis in- 

 creases rapidly during a period of warm, dry weather, but a 

 heavy rain, even when the insect is abundant, will sometimes free 

 the vines almost entirely from it. Unless some weather condition 

 acts in this way to destroy the pest, the only hope of the farmer 

 is for the parasites of the aphis to increase sufficiently jn^ num- 

 bers to overcome and destroy it. 



Summary. 



The pea when grown on a field scale for forage is properly 

 termed ''field pea," but more often "Canada field pea" or ''Ca- 

 nadian pea." 



The field pea is of very ancient cultivation, but was first 

 grown only for human food. 



