354 



THE AGRICULTURAL NEWS. 



July 29, 1916. 



PLANT DISEASES. 



THE POISONING OF WEEDS 

 AND TREES. 



THE PREPARATION AND USE OF WEED-KILLER. Some 



valuable and detailed information on the subject of the pre- 

 paration and use of sodium arsenite for the destruction of 

 weeds is given by G, P. Gray in the Monthly Bulletin of the 

 California State Commission of Horticulture for April 19 IG. 

 The State Experiment Station is conducting an investigation 

 as to the most suitable substances to use, the proper strength 

 at vphicb they should be applied, the time of year to obtain 

 the best results, and the residual effect on the soil. A 

 warning is given as to the indiscriminate and careless use of 

 home-made and proprietary weed killers, which are usually 

 dangerous arsenical poisons. The usual basis of weed-killers 

 is sodium arsenite, prepared by dissolving white arsenic 

 (arsenic trioxidejin water containing washing soda, soda ash, 

 or caustic soda. In the case of the two substances first 

 named it is necessary to boil the mixture to dissolve the 

 arsenic. The proportions of tlie solvent to the arsenic are 

 given as 2 to 1 in the case of washing soda, 1 to 1 in the 

 case of soda ash, and 1 to 2 in the case of caustic soda. 

 A formula is given for using washing soda as follows: — 



Washing soda 

 White arsenic 

 Water 



2 B). 

 1 ft. 

 1 gallon. 



It is suggested that this stock solution should be diluted 

 to 20 or 25 gallons for use, but the actual strength required 

 for any particular purpose must be determined by experiment. 



From a list of cautions necessary in dealing with these 

 substances, the following are quoted: — 



Dont handle or use arsenicals without familiarizing 

 yourself with their properties and behaviour. 



Dont purchase arsenicals without a reliable guarantee 

 of the percentage of arsenic. 



Dont use too small a vessel for dissolving arsenic. 



Dont inhale the steam from boiling arsenicals. 



Dont breathe any of the fumes if any arsenical is 

 accidently spilled upon a hot stove or into a fire. 



Dont boil water, sugar and white arsenic with any of the 

 solvents for arsenic. 



Dont breathe any of the dust caused by handling powder- 

 ed arsenicals. 



Dont make large quantities of stock solution in a closed 

 room. 



Dont splash the solutions. 



Dont spray plants with poisons without taking precau- 

 tions that they will not be eaten by live stock. 



Dont breathe the smoke when burning plants which 

 have been treated. 



The application of the solution may be made by sprink- 

 ling or by spraying, but the latter is very much preferable. 

 It may be u.sed either to kill noxious weeds outright or to 

 prevent them when growing in waste places from seeding 

 and thus infesting adjacent cultivated land. In some cases 

 sufficient poison may be absorbed by the leaves and stems tn 

 kill the roots to a depth of several feet. 



TUii KULiNG OF TREES. One meets rather frequently 

 with an enquiry as to the best means of killing a tree 

 •which for some reason is wanted out of the way. With 



the .species most tenacious of life the operation is not. 

 so easy as is commonly thought. The common method 

 adopted is ringing — the removal of a broad ring of bark 

 or of bark and sap wood. The result depends on the 

 nature of the tree, and is often disappointing. The removal 

 of a ring of bark, provided that a connexion is not allowed 

 to reform, prevents the passage of food materials elaborated 

 in the leaves to the roots. If no suckers are allowed to 

 develop below the ring, the roots eventually die of starvation, 

 but this may be a very slow process. The course of the 

 water passing upward to the leaves is not interfered with, so 

 th<t the top remains green and healthy until the roots die. 

 When a ring of sap-wood is removed as well, the water-supply 

 in the case of those trees with a well-defined heart wood is 

 interrupted, and in this event the top quickly dies. With 

 some other trees, where there is no distinct formation of 

 heart-wood, even this method fails to bring about an early 

 result. Large mango trees, for example, which it was wished 

 to eliminate from cacao cultivations, have been seen to live 

 for years after being thus treated. 



A writer in the Agricultural Gazette of New South 

 Wales for March 1916, reports very successful results from 

 the poisoning of I rees with the arsenical solution discussed 

 above, used at a .strength which may be obtained bj- adding 

 li gallons of water to the stock solution of which the 

 preparation has been described. A ring of downward cuts 

 was made low down on the trunk in such a manner as 

 to leave a frill, and into this the liquid was poured with a 

 watering can made with a long spout and a small exit hole. 

 It is necessary to do this immediately, while the cut is quite 

 fresh, to prevent the blocking of the pores in the wood with 

 air or exuded matter. It is reported that timber thus 

 treated all died, and mostly within forty-eight hours from 

 the time of ringing. 



W.N. 



Substitutes for Lemonade.— Always appreciated 

 in a warm climate, lemonade or limeade, or similar drinks 

 from other citrus fruits are not everywhere obtainable, but 

 good substitutes niaj- be produced from the fruits of certain 

 other trees and plants. Quite accidentally it was found 

 recently that an excellent beverage, which we may call 

 mangoade, can be made from immature mangoes, and that it 

 is quite equal to lemonade in its refreshing (jualities, though 

 of course, differing in flavour. Mangoade is prepared thus: 

 peel, slice, and rinse unripe mangoes, and boil in enough 

 water to cover the fruit; strain the mass tlirough a fine 

 cloth and cool; when serving, add sugar and water to taste. 



By planting seed from time to time throughout the year, 

 rosellade may be had at a very slight expense at all times of 

 the j'ear. 



Rosellade is made as follows ; cut the leaves and tender 

 •stems, rinse, and put in a kettle with enough water to cover 

 the herbage after it is wilted, bring to a boil, strain and cool. 

 Serve as mangoade. 



In both cases great care should be taken to boil and 

 keep the liquids in earthern, granite, enamelled ware or glass 

 in order to avoid poisoning caused by the contact of the strong 

 fruit acids with metals. 



Ripe tamarinds may be made into a delicious cooling 

 drink that is unsurpassed in flavour, and also they make 

 unsually woll-tlavourcd jelly. {Philippme Agricultural 



Review.) 



