ix PESTS IGl 



checking a pest — I quite believe that, as in the case of 

 aphides, there is nothing to beat the human finger 

 and thumb. If dipped in sulphur every now and then, 

 the manipulation will be more efficacious : but even 

 without it, both sides of the leaf can be treated at the 

 same time and the mycelium can be destroyed before it 

 has had time to reproduce itself, without injuring the 

 leaf. 



When the pest is advanced and whole plants covered 

 with readily disturbed fresh spores have to be dealt 

 with, other agents, destructive to the mildew and 

 applied by mechanical means, must be employed. For 

 the plant, so to speak, of the mildew very soon springs 

 from the spawn, and fresh spores are ready in a wonder- 

 fully short time to be borne by the wind to other 

 leaves. 



On touching a shoot infected with mildew on the roof 

 of a greenhouse or anywhere where there is plenty of 

 light underneath, quite a little shower of dust or mildew 

 seed may be seen to fall. Nothing need be feared from 

 those that fall to the ground : they are very short- 

 lived, and cannot stand much of heat or cold, dryness 

 or moisture. Their strength is in their appalling num- 

 bers, and their chances of falling on another Rose leaf 

 depend entirely upon currents of air. 



With the first touch of cold weather in Autumn 

 mildew, as we know it in its summer form, disappears 

 and is seen no more that season, only dark unhealthy- 

 looking marks on the shoots showing where the pest 

 had spread from the leaves to the stems. In such places, 

 and especially on the leaves which are now fallen, the 

 mildew seeds have retired to rest for the winter, and no 

 frost or cold, drought or moisture can harm them. 



These winter places of retreat are tiny black spots, 



M 



