THE DESTRUCTION OF WEEDS BY CHEMICAL 



MEANS. II. 



By HAROLD C. LONG, B.Sc. 



^Aiifliiir of "Coiiniiiiii W'cciis of tlic Farm am! Garden. ") 



Ln the course of his investigations Bollcy obsen-cd : — 

 (1) That succulent plants and those of slow growth arc 

 more easily killed than others : (2) That flower })arts 

 and parts of plants covered with " bloom " or waw 

 coatings are more or less protected ; (i) That jilants 

 possessed of hairy surfaces are, as a rule, more easih- 

 killed th.an those with a smooth surface : (4) That 

 chemicals act differentl\- upon plants of different 

 families, even though 

 the plants he wetted 

 equalh- readih- — char- 

 lock and dandelions, 

 for exami)le.are readih- 

 attacked bv copper 

 sulphate solution, 

 while creeping thistle, 

 \\ild buckwheat and 

 clover are slowh- 

 attacked: and ( 5 ) 

 That most of the 

 chemicals readily de- 

 stroy the tissues of 

 an_\- plant where the 

 surface is broken. 



It was found that 

 charlock could' be 

 sprayed with absolute 

 success ; that king- 

 head or greater rag- 

 weed (A III h r o s i a 

 frificlai could be 

 sprayed in much the 

 same way as charlock 

 and with considerable 

 success at certain 

 times, success depend- 

 ing on the age of the 

 weed ; that creeping thistle (C/z/c7/\ irrvcnsifi) w as most 

 effectively sprayed with sodium arsenite (one-and-a- 

 half to two pounds per fifty-two gallons t)f water). 

 and common salt (one-half barrel per fift\-two 

 gallons of water) ; that succulent portions of the stem 

 and leaves were destroyed when the plants were a foot 

 high and seeding was prevented : that spraying of 

 dandelions on lawns and fields with sulphate Of iron 

 was a marked success ; and that the perennial sow- 

 thistle (Sonc/nis arveiisisi was practicalh' unaffected 

 by sprays. (It may be remarked that this weed, 

 only too common in Britain, is (]uite sniootli and 

 covered with bloom.) 



/■' (>/'/ a /i.'toto^t ,i/>Ji 



Figure 10. 



Garden Kiglitshadc {Solamiiii iiiiiniiii L.) A pest of arable land 



and gardens, and puisonous to an extent which \arics acx'ording 



to conditions. 



Bolley concluded that the following weeds may be 

 eradicated or largeh- subdued in grain fields b\- the use 

 of chemical s\)vayf. : — l'\ilsc Hiix i CcJiiiLiiim scitiva), 

 worm-seed mustard, tmnblinu; imistard, coiunion 

 icild imistdrd : clnirldck I, shcf^hcrd''- purse, pepper- 

 grass, ball mustard, corn aicklt'. chickiceeci. dandelion, 

 cret'pini> thistle, hiudiceed. plantain, rough pigweed, 

 king-head, Ked-Riwr weed, ragweed, cocklebur. 



The following were 

 found not to be effec- 

 tively controlled b\' 

 chemical spra\s as 

 now used: — Hare's-ear 

 mustard, penny cress, 

 pink cockle, perennial 

 stnc-th istle. hi nib' s- 

 quarters. pigeon grass, 

 uilil oats, chess {Broni us 

 secalinus) couch gra.'^s, 

 sweet grass, and icild 

 harley. (In each case 

 those weeds named in 

 italics are of interest 

 to farmers in Great 

 Britain). 



A large number of 

 tests with the sulphates 

 of iron and copper 

 were carried out some 

 years ago hv Dr. A. B. 

 Frank in Germany.* 

 Thirty-five species of 

 weeds were involved, 

 ("lover was but little 

 damaged b\' a 15 per 

 cent, solution of iron 

 sulphate (se\'ent\' 

 gallons per acre, and one hundred and si.\t\' gallons 

 per acre), or a 5 per cent, solution of copper sulphate, 

 the clover soon recovering after losing its first 

 leaves. In addition to charlock, the following 

 plants were more or less damaged b\- sulphate of 

 iron : — corn cockle, poppv, sow-thistle, cornfiower, 

 field thistle, dandelion, groundsel : and the following 

 were more or less damaged b\' a 5 per cent, solution 

 of copper sulphate (se^•ent\• gallons per acre) : — 

 spurrey, groundsel, black bindweed. Though these 

 plants appear to be rarely destroyed they are pre- 

 vented from producing flowers and seed. 



In experiments conducted in 190o at the Holmes 



f'V H. C. l^oiig. 



Bckampfung d. Landw. Un];rUu(er dnrch Mefalsalze. — Arh. aiis. tier Biol. Ahtli. til r Iaiiu!. iiiul /-"or/.su'.. I. Hd.. IMOO. 



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