19(5 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



Only three remedies are recommended to be used in the dry- 

 form, and these have a rather limited use. 



Air-slaked Lime. — This is the powder resulting from the 

 exposure of ordinary lime to the action of the air for some time. 

 It is only recommended as a remedy against insects which have 

 a slimy coating over the body. For these it is a cheap 

 and effectual remedy. It is not as cheap, however, as Paris 

 green, but is particularly recommended where the latter is 

 objectionable because of its poisonous nature. For true slugs, 

 which are not insects, but have a similar slimy coat, it is the 

 best remedy we know of; but it must be applied in the 

 evening or early morning, while the animals are on the plants ; 

 and may have to be repeated two or three nights in succession 

 to kill all. Except in gardens it may not pay to make more than 

 one application, which will, if rightly timed, destroy most of the 

 slugs. 



Sulphur. — This is a widely used remedy for the mildew, which 

 is so common on plants in California. The powder is usually 

 applied by the pepper-box method. It only becomes effectual as 

 the heat of the sun vaporises it ; the field thus treated smells 

 strongly of the sulphur during the warmer part of the day, when 

 the vapour is being produced. On wet cloudy days, when the 

 mildew is growing and spreading rapidly, the sulphur is inert, 

 but the first bright day makes it effective. It may be possible to 

 artificially vaporise the sulphur on a large scale for use in such 

 weather ; but no attempt has yet been carefully made, except in 

 greenhouses, and then with the best of results. The vapour of 

 sulphur must be used, and not the gas produced by burning, 

 which is very injurious to foliage. Sulphur has been found to 

 be a successful remedy for the so-called red spider, also called 

 yellow mite — animals somewhat related to the true insects. 

 Fairly good results are also reported in its use against the thrip. 

 For these purposes the sulphur is used in the same way as for 

 mildew. 



Paris Green or London Purple. — (For a general account of 

 their action, see under Sprays.) These two arsenical poisons are 

 occasionally used in a dry form, but chiefly suspended in water as 

 a spray. They are used for the same purposes in either form. 

 A common practice is to dilute the poison with flour, dust, or 

 other powder so that it can be more easily and evenly distri- 



