54 EXPERIMENT ISTATION RECORD. 



and does not permanently poison the soil. Sulphuric acid ranks next to this, hut is 

 less efficient. For destroying the orange hawkweed in grass lands salt continues to 

 be the best herbicide tested. 



On public measures for the eradication of weeds and other injurious plants, 

 E. KoRSMo {Tidsskr. Norsfse Lanrlhr., S (1901), Xo. 11, jip. o7 1-004). 



The eradication of prickly pear, G. V alder {A(/r-. Gaz. New South Wale.% IS 

 {1902), No. 1, }>j>. 6'J-OJ, pJ. 1). — An account is given of experiments conducted on a 

 hedge of prickly pear which had formed a very dense growth of from 5 to 15 ft. in 

 width. In the preliminary experiment, portions of this hedge were sprayed with a 

 sodium arsenite solution and 2 trade prei^arations, and powdered sulphate of copper 

 was injected into the fleshy stems. As a result of this experiment the sodium arse- 

 nite was found to be much more efficient than any of the others. The copper sulphate 

 gave the poorest results, not completely destroying any of the plants. The sprayed 

 plants all died to the roots l)ut in a few months fresh shoots were developed. As 

 sodium arsenite proved the most suitaVjle of the remedies ti'ied, experiments were 

 conducted to ascertain the best strength of solution. As a result of these experi- 

 ments the author recommends the use of 1 lb. of sodium arsenite to 10 galls, of water. 

 This dissolves readily and is easily sprayed over the plants. The best time for spray- 

 ing appears to be when the plants are most active, which is in spring or summer 

 after heavy rains. The total cost of materials and applications is less than $10 per 

 acre, even on very badly infested land. The action of the spray is rapid and within 

 24 hours the plants seem to be visibly affected. At the end of a week the fleshy 

 stems had all turned brown and within 3 weeks or a month were sufficiently dry to 

 burn readily. The effect of cutting or breaking the plants before spraying was 

 tested but found to be without any advantage. A number of chemicals were injected 

 into the basal joints of the stem of prickly i)ear, but aside from a local disturbance 

 were without any appreciable effect. The substances so employed were sulphuric 

 acid, carbolic acid, potassium oxalate, potassium ferricyanid, sodium arsenite, caustic 

 potash, iron sulphate, and salt. Attention is called to the poisonous nature of the 

 sodium arsenite when used as a spray. To avoid the risk of poisoning, cattle should 

 not be allowed to graze where the treatment is being apjilied. After a week or 10 

 days little danger to stock need be anticipated. The author states that briars, 

 lantana, thistles, and other weeds can be treated in a similar way to that recom- 

 mended for the destruction of prickly pear. 



DISEASES OF PLANTS. 



Crop, orchard, and garden pests, T. W. Kirk {Neiv Zealand Dept. Agr. Rpt. 

 1901, jjp. .317-326). — A Ijrief report is given on a number of the more common dis- 

 eases of farm crojis, orchard and garden products. Among the diseases of orchard 

 trees a description is given of a disease called silver blight, wdiich has been known 

 for a number of years and which continues to spread throughout the country. This 

 disease is readily detected as the foliage, usually beginning upon a single shoot or 

 branch, is seen to assume a shiny, silvery appearance. Later other shoots and branches 

 may be attacked or the disease may not spread farther. Experiments which have 

 been conducted since 1894 led the author to suggest as remedial treatment cutting out 

 of the affected branches and burning them when discovered. There seems to be evi- 

 dence that the disease may be communicated by pruning implements, and on this 

 account it is reconmiended that 2 knives should be employed, the first for pruning 

 until the sound wood is reached, and the second to be used for cutting off a portion 

 of the sound wood. The use of 2 knives may be dispensed wath if the pruning knife 

 be sterilized before making the final cut. The application of iron sulphate to the 

 roots of the plants seems to be beneficial in improving the general condition of the 

 trees. 



