S May, 1908.] St. John's Wort. 267 



ST. JOHN'S WORT. 



Notes on Results of Chemical Weed Eradicators Experimented 



WITH. 



H. II". Dave) , Inspector, Vegetation Diseases Acts- 



In order to form an idea of the effect of chemical weed exterminators 

 after several years, I revisited Bright on the 29th January to inspect the 

 plots treated with chemicals for the suppression of St. John's Wort. 

 I found the plots treated with Murton's Weed Killer during February, 

 1905, covered again with the weed, partly from the recovery of old 

 •established plants and partly from seedlings. These plots are in the 

 Racecourse reserve running parallel with the Harrietville Road : the plots 

 facing the grand stand are all covered with the weed but it is rather 

 stunted as compared with the untreated weed outside the plots. 



The three acres on the Harrietville Road which were fenced in for 

 treatment are all once more infested. Plot 12 in this area was treated 

 with ^ ton of salt on 29th November, 1904, and the weed was destro\ed 

 but the land has been reinfested from seeds washed down from land 

 higher up the hill ; the plot is on very steep land and every rain must 

 wash a lot of seed down. Plot 11 in same paddock, treated with Invicta 

 in October, 1904, is on the level country below the race and the kangaroo 

 _grass has held its own against the w^eed fairly well. In some spots the 

 grass has beaten the weed badly, but I put this down to the moisture 

 being especially favorable to the grass and adverse to the deep roots of 

 the weed. Seed from the weed has not much chance against the grass 

 especially as the latter is protected from being eaten out by stock. 



The only plots that look well are those adjoining the saddling paddock ; 

 these were treated in No\ember, 1904. No. i plot treated with Bethanga 

 pyrites, is still absolutely free of weed, except where a track cut by 

 wood drays crosses it. On this track the weed has firmly established 

 itself once again, but cannot encroach on either side of the track, proving 

 that once the surface was broken by these ruts the rain washed the 

 arsenic out of the soil and allowed the seed (which must be verv plentiful 

 in that locality) to germinate. The wav in which the plant is confined 

 to this track gives it a remarkable appearance. Plot 2 treated with arsenate 

 of soda is fairly clean but the land is gradually recovering, and the weed 

 is always at hand to grip the spot where rains have leached the arsenic 

 out of it. Plot 3 (iNIurchison Scrub Exterminator) is the next best, then 

 Plot 5 with Invicta, but the plots treated with Silex and Murton's Dip 

 are both badly covered again with weed. 



From the foregoing observations it appears to me that salt comes first 

 as a remedy as it will kill out the weed and its etfects on the soil are not 

 so lasting as arsenical preparations or as dangerous, but unless land 

 treated with salt is protected against fresh supplies of seed being blown 

 or washed on to it, it is only a waste of labor. With regard to strong 

 arsenical solutions the Bethanga plot proves that the weed can be utterly 

 destroyed by strong arsenical solutions for lengthened periods — in this 

 instance from 4th November, 1904, up to the present. This treatment 

 would be useful for headlands; the weed growing in the wheel ruts on 

 the Bethanga plot shows that arsenic killed land can be recovered bv 

 cultivation which allows the rains to wash out th? poison. 



