35'2 INSECTICIDES, FUNGICIDES, AND WEED KILLEES. 



of bird-lime are applied about o feet al)ove the surface of the 

 ground. It may be applied directly on the bark of old trees. With 

 young trees the treatment is risky. Hartig and Sorauer found that 

 thin-barked young trees are sensitive to bird-lime, and the bark, being 

 penetrated by it, the tree dies in a few years. When young trees are 

 to be protected, the trunk of the tree is encircled by a band of paper 

 11 centimetres (say 4^ inches) wide, which is coated with bird-lime. 

 It is well to keep the ring on all the year round and to renew it 

 whenever it loses its stickiness, say about every three months. The 

 ring of bird-lime is much more effective than the classical tar ring ; 

 like the latter, it retains all the apterous insects which ascend from 

 the soil on to the tree by the trunk, or which descend by the same 

 road to metamorphose in the soil. Thus the Cheimatobia brumata, L., 

 and the Hibernia defoliaria, L., apterous phalena, the larva of 

 Eriocampa admnbrata, and the Psylla of the pear-tree are easily 

 destroyed in that way. 



Schizoneura lanigera, Hausm. (woolly aphis). — To combat this 

 aphis Clarac recommends to coat the spots invaded by colonies, that is 

 to ssbj, all the bark, by a mixture made by heating 2 lb. of tallow, 

 3 lb. of rosin. 5 lb. of poppy or colza oil. 



(3) Bouillies. — Rosin is added to increase the adherence of a 

 copper bouiUie. The following formulae may serve as a guide : 1. Blue 

 vitriol 12 lb., lime 15 lb., rosin 6 lb., soap 7 lb., water 100 gallons. 

 2. Blue vitriol 12 lb., rosin 15 lb., soap 6 lb., water 100 gallons. 



130. Camphor, G^^^H^^fi. — Natural Occurrence. — Camphor is 

 extracted in China and Japan from old camphor trees, Laurus cam- 

 2)hora, by sublimation — heating the roots and branches. It is refined 

 in Europe by fresh sublimation. 



Properties. — Camphor is a white, semi-transparent, crystalline 

 substance. It has a characteristic, fresh, aromatic odour. Its density 

 is from 0-992 at 10' C. It melts at 173° C. and boils at 204° C, but 

 it volatilizes perceptibly at the ordinary temperature. Water dissolves 

 1 part in 1300 at 20° C. Alcohol and oils dissolve it freely. Camphor 

 is a poison of the protoplasma ; even in dilute solution its antiseptic 

 power is known. It has been used from the most remote times. It 

 has a poisonous action on the lower animals, chiefly the arthropodes, 

 which are killed by the vapours emitted by camphor at the ordinary 

 temperature. 



Use. — Phylloxera vastatrix, Planch, (phylloxera of the vine). — 

 From 2-3 grammes of camphor run into a hole dug by a gimlet, as far 

 as the pith of the stock, and then corked, had a certain action on the 

 phylloxei"as of the roots, but destruction was incomplete (legal process, 

 1872). Watering the ground round the stem with a bouilhe of 10 lb. 

 of camphor, 25 lb. of ammonia, and 25 lb. of lime, had no good effect. 



Mice. — To protect seed-corn from mice it suffices to mix it with a 

 little camphor before sowing it. The smell drives off' the rodents. 



