338 INSECTICIDES, FUNGICIDES, AND WEED KILLEES. 



found, however, that far from iiijurint:^ the trees, the layer of tar, if it l)e 

 not too thick, may act as a tonic to the wound and favour cicatrization 

 and thus enal)le it to cover itseU' with fresh hark. Boiteau ohserved 

 on stocks treated with tai- rather grave disorders at the heginning of 

 growth : a dehxy in the latter and chlorotic vine leaves which disappear 

 later on. Sajo has observed that tar, especially wood tar, is injurious 

 to dormant eyes. According to Berlese and Fleischer, soUitions of tar 

 in alkali diluted with water are injurious to the leaves above 5 per cent. 

 Sprayings should never be done during flowering nor before the fruit 

 has formed. 



Action on Insects. — Tar is insecticidal by contact, but its action 

 is not intense, and it requires strong doses to kill insects. In strong 

 doses it kills the eggs of butterflies ; in solution in caustic alkalies con- 

 taining 2-4 per cent of tar it kills insects with soft skins, such as lice 

 and caterpillars ; from 1-5 per cent it kills Orthoptera, Hymenoptera, 

 Lepidoptera, and Diptera (Berlese). The larvae of the saw-flies are 

 killed by 5 per cent emulsions (Sonnino). 



Use. — Bituminous shale was used by the Greeks to keep off insects. 

 In our days tar is used as it is to destroy the mass of butterfly eggs, 

 and to form around the trunk an impassable barrier, and a trap to 

 apterous insects and their larvaB, which are obliged either to descend the 

 tree to continue their metamorphosis in the soil or to ascend the tree 

 along the trunk after their transformation into a perfect insect. The 

 bouillies obtained by mixing tar, more especially wood tar, with caustic 

 alkali, alkaline carbonates, or with soft soaps, are used in spraying in- 

 sects with a soft skin. A preparation, sold under the name of •' Eubinia," 

 and greatly used, is prepared by boiling 50 parts of wood tar with 50 

 parts of caustic soda, 30° B. This preparation is soluble in distilled 

 water with a red coloration ; it should be diluted with rain water. Tar 

 bouillies are also made containing blue vitriol, naphthalene, and lime. 

 Howard recommends a bouillie of blue vitriol and tar, obtained by 

 stirring energetically 6| lb. of coal tar with 5 gallons of boiling water 

 into which there is poured when the emulsion is complete, and after 

 removing the blackish froth, a solution of 12 lb. of blue vitriol in 5 

 gallons of water. Tetard recommends an emulsion with petroleum 

 and carbolic acid made thus : Heat 6 gallons of tar ; remove from the 

 fire and add while stirring 3 litres of petroleum and 10 litres of 

 carbolic acid. Balbiani recommends a mixture of coal tar, naphthalene, 

 and lime prepared thus : Dissolve 3 lb. of naphthalene in 2 lb. of coal 

 tar, and pour the mixture into 100 lb. of lime slaked with a little water. 

 After intimately mixing these substances they are gradually thinned 

 by adding 40 gallons of water. Eathay recommends an analogous 

 bouillie containing 4 lb. of coal tar, 12 lb. of naphthalene, and 24 lb. of 

 lime in G gallons. " Pitteliene " used in Italy is a mixture of oil and tar. 



Use to Destroy Weeds. — One of the most efficient methods to free 

 paths and roads from weeds consists in watering them with an emulsion 

 of equal parts of water and tar. The weeds do not grow again for two 

 years. But it has the disadvantage of being as dear as hoeing and of 

 browning for some time the spots treated. However, it is expeditious 

 ^nd kills earth-worms at the same time. 



