LEGUMES FOR SEED 233 



vided care is taken to use one that does not split the seeds 

 while planting, which, sometimes occurring, causes quite a 

 reduction in the stand. The rate of seeding varies from 1.5 to 

 3.5 bushels per acre. 1 The Ontario Station, after testing for 

 six years, found that by selecting seed for sowing, the results 

 showed an average of 28.1 bushels per acre from large seed, 

 and 23 bushels from small seed. 2 



280. DISEASES AND INSECTS. Diseases rarely do much damage to field peas. 

 Field peas are sometimes severely damaged by blight (Ascochyta pisi Lib.) 

 and occasionally attacked by the powdery mildew (Erysiphe polygoni D. C). 

 The latter may be checked by spraying with Bordeaux mixture. In the absence 

 of a successful remedy for the former, planting sound seed in soil free of 

 the fungus may serve as a prevention. 3 While other insect attacks occasionally 

 occur, the one enemy to pea culture, and especially to the production of 

 sound seed, is the pea weevil (Bruchus pisorum L.). This is larger than the 

 bean weevil, being about one-fifth inch long. This insect lays its eggs upon 

 the young pea pods, which upon hatching burrow into the pea, never more 

 than one weevil to each pea, where, as the seeds mature, it lives and develops 

 into an adult beetle. In the green peas, the minute dot by which the larva 

 entered is not ordinarily noticed and consequently the larvae are often con- 

 sumed in large numbers. In dry seeds, the cell inhabited by the insect may 

 be seen under the skin, while later the adults bore holes in the skin through 

 which they escape. Unlike the bean weevil, they do not breed in dry seed, 

 and there is only one generation; hence if prevented from laying their eggs 

 upon the pea pods, they must perish. 



Advantage is taken of this fact in two ways: (1) If infested seed is held 

 in a tight receptacle until the second year, all insects perish, and the seed 

 may be planted without being the source of the insects. Infested seed, how- 

 ever, is very low in germinating power, and seed which germinate are often 

 mutilated and of little value. (2) If seed are planted late after the breeding 

 of the insects, peas may escape attack and sound seed may be secured. In- 

 sects may be destroyed, also, by the same means mentioned for the bean 

 weevil. (271) The pea weevil is less active in the northern tier of states 

 and in Canada, which accounts, in part, at least, for the culture of field peas 

 being restricted largely to that region. 



In Canada it was found that by suspending culture of the crop, at the 

 end of three years the weevil was almost completely eradicated. Treating 

 with carbon bisulphide immediately after threshing has also resulted in their 

 complete destruction.* Spraying the vines with Paris green just after the 



1 For method of seeding with oats, see (C. A. 405). 



- Ontario Agr. Col. and Expt. Farm Rpt. 1905, p. 191. 

 3 Ohio Sta. Bui. No. 173 (1906), pp. 233-246. 



* Ontario Agr. Col. and Expt. Farm Rpt. 1905, p. 191. 



