THE DESTRUCTION OF WEEDS BY CHEMICAL 



MEANS. 



Bv HAROLD f 



LONG. B.Sc. 



{Author of "Common Weeds of the Farm and (Jitrilen .") 



During the past twenty vears an increasing amount 

 of attention has been devoted to the economic side 

 of insect and fungous pests, with a view to their 

 extermination, and The Destructive Insects and 

 Pests Act of 1907 gives the Board of Agricuhure 

 and Fisheries power to deal with the whole question, 

 and carry out compulsory pre- 

 ventive and remedial measures 

 in the case of such species as 

 they consider of sufficient 

 importance to schedule in their 

 Orders.* The attention of 

 scientific workers has for many 

 years been turned to the 

 necessity of acquiring a 

 thorough knowledge of the life- 

 histories of all the worst insect 

 and fungous pests of the farm, 

 garden, and orchard, and a vast 

 fund of information has been 

 acquired b\' a s\stematic study 

 of individual species. Such 

 stud\ . in conjunction with 

 experimental work, has been 

 necessarv in order to eradicate 

 the particular pest concerned, 

 and here also much has been 

 accomplished, even though it 

 be said that much remains to 

 be done. 



What, however, is the posi- 

 tion in regard to the prevention 

 and eradication of the common 

 weeds of the farm and garden 

 which annualh" cause so much 

 loss to the grower of crops ? 

 It may be said that a good deal 

 has been done to enable the 

 unbotanical worker to identify 

 species, and a few practical botanists and 

 agriculturists have offered sound advice as to 

 the mechanical destruction of weeds. Yet the 

 information available is still quite inadequate, and 

 while some of the highly farmed lands are more 

 or less \\eedless, the majoritv of farmers meet with 

 two or three species of weeds which they experience 

 extreme difficulty in combating. The question of 

 weed eradication is one of real difficult}', and when 

 we bear in mind the fact that man\- serious insect 



Figure 1. 

 Charlock {Sinapis arvcnsis L.) X -;. This 

 weed is readily destroyed b\- spraying with a 

 solution of copper sulphate or iron sulphate 



and fungous pests are supported and distributed by 

 weeds, it assumes an importance which the entoirio- 

 logist and mvcologist would do well to recollect. 

 Professor Somerville has written : + " Using the 

 term in its wisest sense gootf cultivation will be found 

 to be the best protection that the farmer or gardener 

 can offer his crops against 

 insects," and good cultivation 

 includes the destruction of 

 weeds. In many countries the 

 importance of destroying weeds 

 has long been officially recog- 

 nised, and Acts have been 

 passed requiring the destruc- 

 tion of specified \\eeds. In 

 Great Britain, however, the 

 onl\- laws of the kind refer to 

 Ireland and the Isle of Man. 



The Prevalence of Weeds. 



We have said that some 

 highly farmed lands are more 

 or less weedless, but it is 

 undoubtedl}- true that most 

 farms are far more weedy than 

 thev either ought to be or 

 need be. In the third week of 

 August. 1909, we found in an 

 area of perhaps a hundred 

 square vards of a wheat field no 

 less than twenty-nine species 

 of weeds, the majority of which 

 were among the most trouble- 

 some of all (including the 

 species illustrated in Figures 

 1, 5, 6 and S). Similar cases 

 could be quoted. We consulted 

 twentv-nine experts in different 

 parts of the country, from the 

 North of Scotland to the South of England, and 

 species of " couch or twitch '" were included thirty- 

 two times among the six worst weeds of arable land, 

 charlock and runch twenty-eight times, docks 

 sixteen times, thistles sixteen times, coltsfoot 

 thirteen times, and so on. -As regards grass land, 

 thistles were regarded as the worst in twenty-two 



cases, buttercups sixteen, Yorkshire fog (Holcus 

 lanatiis and H. mollis) nine, docks eight, and so 

 forth. These figures show that the species named 



The Destructive Insects and Pests Order of IQIO, schedules si.xteen ■'destructive insects and pests.' whose presence on any 

 premises must be notified to the Local Authority or to the Board of .•\griculture and Fisheries. 



t Farm and Garden Insects, p. 30. 



391 



