MILDEW. 281 



by the frost, simply afforded a congenial " soil, " for the 

 mildew germs, which probably are ever present in the 

 atmosphere. 



Had the sap been arrested by the roots getting dry in 

 that condition of growth, no doubt the result would 

 have been nearly the same. 



Like most other diseases, mildew is best met by pre- 

 vention rather than cure, and for this reason, all care 

 should be taken to avoid the extremes referred to, as far 

 as possible, to avoid great variation of temperature. 

 Sulphur is applied in various ways to destroy mildew, 

 but will often fail if the disease has gained much head- 

 way. The best way is to use it mildly as a preventive. 

 This is done by boiling three pounds of sulphur and 

 three pounds of lime in six gallons of water until it is 

 reduced to two gallons; allow the liquid to settle until it 

 gets clear, then pour it off and keep it in a jar, or bottle 

 it for use. One gill of this is to be mixed in five gallons 

 of water and syringed over the Roses in the evening. 

 Applied in this weak state it does not injure leaves, and 

 yet has the effect of preventing mildew, if perseveringly 

 attended to, as the spores of mildew seemingly cannot 

 vegetate in an atmosphere or in a soil impregnated with 

 sulphur. The above preparation is Sulphite of Calcium. 



Another method is, to dust the leaves very lightly with 

 " Black, " or " Virgin Sulphur " the only reason this 

 kind is used in preference to the ordinary yellow sulphur 

 is, that it is more volatile and can be used to give a lighter 

 covering to the foliage, answering equally well and being 

 less unsightly. We use one or the other of these methods 

 once a week during spring or summer on our Roses, and 

 thus keep almost entirely clear of mildew on all Roses 

 grown under glass. 



But the most common and most efficient application 

 of sulphur against mildew in the greenhouse, after firing 

 has begun, is to paint the upper half of the hot-water 



