1906 ENTOMOLOGICAL SOCIETY. 115 



They seldom have a tendency to cluster, if there be few in number, but, 

 instead, are scattered somewhat evenly on the bark. 



On badly-infested trees the presence of the scale on new growths and 

 the fruit produces a deep-red coloration on the tissues of the bark. 



It leaves no conspicuous, ventral, whitish scale on the bark after the 

 removal of the insect, as does the Scurfy Bark-louse. 



The reason for considerably more damage being done by the San Jose 

 Scale than by the Oyster-shell Bark-louse is on account of the San Jose Scale 

 producing many broods in one season, and also bringing forth its young 

 alive, whereas the Oyster-shell Bark-louse is one-brooded and winters over 

 in the egg stage. 



The treatment to be adopted for nearly all the scales is practically the 

 same in all cases. On deciduous trees, where the scales remain during the 

 winter upon trunks and branches, and where the trees become dormant, the 

 scales are best treated during the winter. At that time there is no foliage 

 to interfere, and much stronger washes can be used than would be possible 

 during the summer, or when the tree is active. It is extremely difficult io 

 penetrate insect tissues with ordinary liquids, and it has been found impos- 

 sible in practice to obtain good results in the destruction of scale insects, 

 except by means of caustics. The common soaps are all caustic, and, when 

 applied in strong solutions, the scale is shrivelled, lifted, and partially cor- 

 roded, so that the oily mixture works its way beneath into absolute contact 

 with the insect. Or it is raised at the edges and washed off by the rains, 

 carrying with it either eggs or young, as the case may be. In fact, where 

 the eggs hibernate, winter applications act only by exposing them, so that 

 they are easily washed away by rains and scattered. 



In the case of plants which do not lose tKeir foliage at any period, or 

 in conservatories, or where winter treatment for any reason is not feasible, 

 we must attack the insects when the larvae are crawling about, and before 

 they are fixed. At that time, whilst not protected by a scale, they may be 

 easily killed, almost any of the contact insecticides being effective. 



Remedies .—Owing to the large number of applicants who were desirous 

 of obtaining information on the best methods of combating the Oyster-shell 

 Bark-loiise, it w-as decided to carry on a number of experiments here, to test 

 the efficiency of the various insecticides commonly used against scale insects. 



Of all the spray mixtures tried, the well-known lime, salt and sulphur 

 wash gave the best results. 



The lime, sulphur and caustic soda, and the lime, sulphur and sal soda 

 were also tried, but wdthout quite such good results. The lime, sulphur and 

 caustic soda proved to be a little superior to the lime, sulphur and sal soda, 

 , owing to its apparent power of better penetration. 



Soaps. — Yarious soaps were also tried, and of these the Whale-oil Soap 

 Emulsion gave the best results, many of The scales being killed. 



The Whale-oil Soap gave good results also, but not equal to the Emul- 

 sion . 



Sunlight and Lifebuoy soaps, and also a mixture of both, proved to be 

 of very little value, inasmuch as they did not prevent the eggs from hatch- 

 ing. These soaps are claimed by the makers to be most effective against the 

 San Jose and other scale insects, but applied as a winter wash against the 

 Bark-louse they have little value. Undoubtedly they should be applied 

 after the young lice hatch, and not as a winter application, and then would 

 most likely prove effective against the tender lice. 



