TENTH ANNUAL YEAR BOOK— PART VI 575 



Use of chemicals. — Many farmers have applied salt, kerosene, lime, and 

 other substances for the purpose of killing the underground parts of the 

 bindweed. One difficulty with this method is that on account of the 

 habits of the roots and rootstocks of bindweed such applications must be 

 spread all over the infested area, which makes the cost so high that these 

 materials can be used profitably in only a limited number of cases. An- 

 other difficulty is that a quantity sufficient to kill the weeds will also in- 

 jure the land to such an extent that no crops can be grown for several 

 years subsequently. Crude salt is probably the cheapest material for the 

 purpose. 



Tests have been made by agricultural experiment stations and farmers 

 to kill bindweed by repeated applications of salt, iron sulphate, arsenite of 

 soda, and other chemicals in solution as sprays. Such experiments have 

 failed to show that this method is of any value. Although the tops are 

 killed to the ground new plants immediately spring up. The sprayings 

 must be given once every few days during the growing season for at least 

 two years before the weed finally ceases to grow. The result can undoubt- 

 edly be accomplished in less time and with less expense by some other 

 method. 



SUMMARY. 



(1) The names bindweed and wild morning-glory refer to the several 

 species of the genus of plants known as Convolvulus that are considered 

 weeds, including primarily hedge bindweed {Convolvulus sepium) and 

 field bindweed (C. arvensis), two other species, Convolvulus sepium re- 

 pens and C. califomicus, being of secondary importance. 



(2) These weeds are a very serious detriment to the growing of crops 

 in many regions. They are especially important in cultivated crops, are 

 sometimes of a serious nature in small grain and orchards, but do no 

 serious damage to forage crops. 



(3) Bindv.-eed usually occurs on bottom lands and rich prairie soils. 

 It is sometimes found growing in patches, but it is more common to find 

 it distributed more or less generally over the field. Its depth of rooting 

 is governed largely by the nature of the soil. 



(4) The underground parts are of two forms, exemplified by hedge 

 bindweed and field bindweed; the first is propagated by rootstocks and the 

 second by roots. The nature of the underground parts of both of these 

 forms indicates that the top growth must be kept down, thereby starving 

 out the roots and rootstocks, in order to eradicate the weed. 



(o) Several methods for accomplishing this eradication have been suc- 

 cessful. Clean cultivation is one of the best in many cases. It is essential 

 to employ such implements as will keep down the top growth successfully. 

 Where the weed occurs in patches these should be marked off and given 

 special attention. 



(6) The bindweed may be greatly reduced or entirely destroyed by 

 seeding the land to alfalfa. The frequent cutting and the shading effect 

 of this crop are the determining factors. Alfalfa should be followed by a 

 cultivated crop to complete the w'ork of destruction. 



