MAY. 93 



THE VINE MILDEW. 



{Oidium Tuckeri.) 



Although this pest has received many hard blows from gardeners of 

 energy and determination, yet I fear that much misapprehension still 

 exists on the subject generally. Without pretending to throw much, 

 if any, new light on the cause of the evil, perhaps three years' experi- 

 ence and observation of its efects may not be unacceptable. Might 

 I also be permitted to take this opportunity of strongly protesting 

 against the statements of those who presume to say that mildew has 

 never attacked t/ieir vines because of their own uniform good treat- 

 ment, which has acted as a preventive. This is all a mistake ; for 

 although we may alleviate and even subdue the fungus when it shews 

 itself, I firmly believe that the primary cause of its appearance is, at 

 least at present, beyond the reach of both practice and science. 



Whatever this first cause may be^ I have no doubt that the evil 

 is aggravated by a cold atmosphere. It is also extremely local; for 

 I have seen vineries infested in comparatively low situations, while 

 those on higher ground, in the immediate neighbourhood, have been 

 entirely free from it. Another favourable condition for the develop- 

 ment and subsequently rapid propagation of mildew, is a cold, strong, 

 retentive soil, filling both old and young wood with crude unassimi- 

 lated sap, rendering leaves, shoots, and fruit, in their earlier stages, 

 more easily assailable by the insidious foe, and shewing the para- 

 mount importance of having the wood thoroughly ripened. This fact 

 may be constantly observed during the summer months, w^hen out- 

 door vines are completely smothered as with flour ; from which we 

 may infer that no bad management can be essentially the cause of 

 the indoor malady, how much soever it may afterwards encourage 

 and disseminate it. 



From the foregoing observations it may be gleaned that vines are 

 more susceptible of disease w^hen exposed to the separate or com- 

 bined influences of cold atmosphere, cold retentive soil, or a low 

 situation. Of these, a cold atmosphere has perhaps the greatest in- 

 fluence, as I have always observed that the more cold air admitted, 

 without strong fire-heat to counteract it, the worse the disease has 

 been. Grapes, having the appearance of being thrashed,, as it were, 

 with rods, is owing to denuding the vines too suddenly of laterals 

 and foliage, when the fierce rays of a summer sun injure the tender 

 skin. By many this eff'ect is supposed to be caused by mildew, and 

 it is more frequent under sheet-glass than any other kind. Muscats 

 are especially liable to this accident. 



Now, premising the above conditions to be favourable to the in- 

 crease of mildew, the cause of treatment to be pursued in order to 

 save the crop from ruin when attacked is sufficiently obvious and 

 simple, and may be summed up in a few brief directions : Keep up a 

 strong-fire heat, but let that be guided by sound judgment; economise 

 sun-heat, to ensure an early and thorough ripening of the wood ; ven- 

 tilate carefully and cautiously, to avoid cold draughts and sudden 

 changes of internal temperature ; if possible, only give air at the top 



