PINE MOTH. 



301 



I 



must be put on cold. Coal-tar must not be used for this 

 purpose. 



Certain compositions are also used which are superior to 

 tar, such as tar mixed with 9 to 15 per cent, of resin, or 

 9 to 11 per cent, of acetic acid. For similar purposes in 

 England, grease-bands are made of "cart-grease" or mix- 

 tures of Stockholm tar, unboiled linseed-oil, etc., etc. 



In order that a composition may be really useful for this 

 purpose, it must combine cheapness with prolonged stickiness. 

 A thick coating should always be used, or else the substance 

 is absorbed by the bark. 



In order to spread the tar 

 a paint-brush was- originally 

 used, but Boden and Kielmann, 

 two German forstmeisters, con- 

 structed, in 1881, two wooden 

 spatulas, which Fig. 151 repre- 

 sents. The broad and grooved 

 spatula is about 36 cm. long and 

 5^ cm. broad at the top, where 

 it is grooved on one side, but 

 smooth on the other. The 

 grooving gradually slopes from 

 the handle to the extremity of 

 the spatula, where it is 5 mm. 

 deep. The tar is taken from 

 the barrel on the flat side of the 



broad spatula, and spread on the tree with the narrow spatula. 

 The broad spatula is then turned round, and the groove 

 pressed round over the tar. This makes a smooth ring 5 cm. 

 broad and "5 mm. thick. 



The quantity of tar used and the cost of painting the rings 

 varies with the age of the woods, and in Prussia averages 40 

 to 50 lbs. per acre for old wood, and 50 to 60 lbs. per acre for 

 young wood, the average cost in either case being 6.s-. and 

 9s. 6(1. per acre for tar. 



In 1878 in Plietnitz in West Prussia, 45 millions of cater 

 pillars were destroyed by means of tar rings, at a cost of Is. 

 per 10,000 caterpillars. In woods under 60 years old the 



U 



Fiff. 151. 



