104 INSECTICIDES, FFNGICIDES, AND WEED KILLERS. 



soda. Mohr advises a mixture containing 4 per cent alum and 5 per 

 cent amylic alcohol (fusel oil) to destroy larvae without down at the 

 moment they are hatched from the winter egg [Nov. -Dec.]. But this 

 mixture does not seem to kill eggs and adults. The role of amylic 

 alcohol in the destruction of these larva; is not unimportant, for no 

 appreciable result was got in recent trials made with concentrated 

 solutions of alum alone. This method is, moreover, contested by 

 ]\ruhlberg. Advised by Eadan in 1872 to combat the phylloxera 

 Mouillefert found the dose of 100 grammes of alum (say 31 oz.) per 

 stock without action on the insect but apt to kill the vine. 



56. Silicate of Alumina (clay). — Occurrence. — Pure silicate of 

 alumina is known as kaolin (" china clay ") and " plastic clay " ; mixed 

 with carbonate of lime it forms potters' clay. 



Properties. — Mixed with water, clay forms a supple, plastic, and 

 unctuous paste. 



Use. — In virtue of its special properties clay is used to guarantee 

 the bark of trees against the bites of leporides or to asphyxiate xylo- 

 phagous insects. For this purpose it is mixed with cow-dung and often 

 with ox-blood or curdled milk The following insects inter alia may 

 be got rid of in this way : — 



Agrilus sinuatiis, 01. (burn-cow of the pear-tree). — To prevent 

 the burn-cow from laying its eggs the trunks and branches of the tree 

 are coated with potters' clay ; to fight the larvte and asphyxiate them in 

 their burrows the whole of the bark must be coated with a mixture of 

 potters' clay and cow-dung, and a band of cloth applied on this coat. 

 Goethe found this treatment good. It can also be used against scolytes 

 and bostriches such as Scolijtus Pruni, Eatzeb. (scolytus of the plum), 

 Scolytus rugulosics, Koch (rugose scolytus), Toviicns dispar, Fbr. (bos- 

 triche different). To protect fruit trees against these three insects the 

 trunk and branches are coated with a mixture of lime and clay. 



Cochineals. — To kill cochineals a very old method consists in 

 coating the trees invaded with the following composition : Clay, soot, 

 cow-dung, sulphur beaten up with water to a pasty consistency. 



Rabbits. — To prevent rabbits from nibbling the bark of fruit trees 

 these are coated at their base with one of the following preparations : 



(1) Potters' clay 2 lb., cow-dung 2 lb., ox-gall 1 lb., bullock's blood 

 1 lb. This mixture is stirred up with purin to a pasty consistency. 



(2) Potters' clay 2 lb., curdled milk 2 gallons, blood 2 gallons, puiin 

 6 gallons. (3) Asafetida 1| lb., blood 8 gallons, with sufficient cow- 

 dung and clay to give a smooth paste. The odour of these coatings 

 being very repugnant to rabbits keeps them at a distance. 



57. Zinc Sulphide, Zn8. — ^Preparation. — By adding sodium sul- 

 phide to a solution of zinc sulphate. The white precipitate is filtered 

 and washed. 



Properties. — Zinc sulphide is insoluble in water. 



Use. — Fairchild used a zinc sulphide bouillie, made by precipitating 

 sulphide of zinc by a solution of liver of sulphur against (1) Phyllo- 

 sticta sjjJuerojysidea, E, and J^l (spots of the leaves of the chestnut) and 

 against (2) Entovisoporiuvi viacnlatmii (spots of the leaves of the pear- 

 tree). Result in (1) appreciable, in (2) nil. 



