Many Weeds Can be Controlled by It is evident that 2,4-D will destroy 



Using the New Chemical Herbicides. Canada Thistles provided that sever- 



Experiments were carried on in 1947- al applications are made, starting 



48 in an attempt to find effective early in the summer. 



ways of killing thistles. There are T * n a j 



J , . . ! & r ,, ... In recent years , two yellow-flowered 



several kinds ot troublesome thistles • r r» -r r> ■ ..l u 



AT TT , . „, „ . species of Devil s Paintbrush or 



in [New Hampshire. Ihe Canada n 1 j 1 i i 



„, . , . r • i i • i i nawkweed have become very abun- 



Ihistle is a perennial which spreads j + • c u j -vr 



. i t , . dant in fields and pastures in New 



extensively and becomes very serious Hampshire One the Mouse-ear var- 



■ • i| 11*11 i •! iiaiuuciiiic. vync ? nic lUUUSC'Cal Veil- 



once it is well established, while sev- • . u ■ ■ -in i 



, , . i ii i let V tlier actum pilosella, spreads ex- 



eral other species commonly called . • i i i 



n ii t,, . ,1 r t . -ill- tensively by runners over large areas 



Dull Ihistles are biennials and die f f i j ,. • . f . .i 



- a . . , . , to the detriment ot most other vege- 



atter flowering in their second year. . .• rn , ,, , y . r» -i 



. „ . b . , , . : . tation. Ihe other, called King-Devil 



All species are bad weeds particular- (H florentinum) , is a taller lant 



ly in pastures. Much work has been and occurs in scattered clumps . The 



done over the years in the United Ki Devil d hard to m with 



btates and Canada on the control of both 24 . D chemicals and ammate 



Canada Thistle. Recently, there have but Qn geveral , ots Ae Mouse . ear 



been many conflicting recommenda- u„ i i . i . ha 



} . & riawkweed was at least 90 per cent 



tions as to suitable 2A-D treatments j_ f „ j u ■ 1 ^• I- t 



. ' destroyed by single applications ot 



tor its control. the most recent .1 „ f i i ju»i * t n a n 



.... . . .. the methyl and butyl esters ot 2, 4-D 



work indicates that several applica- ,. T v „ . „. . i . a 



. _ . _ , , - 1 . 1 ., . when treatments were made at Hower- 



tions ot z, 4-U are needed to kill the • „ f ; • i ♦ t t>u o a t\ 



... ' . . _. ing time in late June. Ihe 2, 4-D 



thistle completely Our treatments wag uged flt R concentration of 1000 



were directed at the Canada Thistle tg milHon of water 



but in most cases some Bull thistles , . 



also were included. Several different Ther f has , been ^ bellef \ n Ne ^ 



chemical forms of 2, 4-D were used Ham lf hire that 2 ' 4 " D ls n » l d ep end " 



at the usual recommended concentra- abIe f f P^son-Ivy control Where 



tion for general weed control of 1000 areas have b f n treated , wltb ?' 4 -°' 



parts per million in water solution, f considerable regrowth of the ivy 



A i /- i ti i has frequently occurred. It was de- 



Ammate and Granular Borax also • i j c .. o a r\ *u 



, , . cided hrst to compare z, 4-D with 



were used, the animate at the rate i i r> • t i -n 



e ii r i better known roison-lvy killers, 



ot 5 ounces per gallon ot water, the 



borax at from 1 to 3 pounds per hun- Plots were laid out on June 12 usin S 



dred square feet. The Canada This- (1 ^ borax at 4 pounds per 100 



ties were killed to the ground by the s q uar e feet, (2) ammate at % pound 



ammate, but after two or three weeks P er gallon of water per hundred 



new shoots appeared from the sur- square feet, (3) the ammonium salt 



viving underground parts. Borax of 2, 4-D at 1000 parts per million 



was not effective in thistle control. of water, and (4) the methyl ester 



All the 2,4-D applications resulted of 2, 4-D at the same concentration 



in partial controls of Canada Thistle as the salt. The borax and ammate 



with no particular formulation out- gave complete kills; the methyl ester 



standing. On the plots treated with was entirely effective only after a 



2, 4-D, only about one third as many second application. The ammonium 



stalks appeared the following year as salt of 2, 4-D was considerably less 



were present at the time of treatment, satisfactory than the methyl ester, 



Most of the Bull Thistle plants sur- which agrees in general with reports 



vived all treatments. from other workers. 



11 



