GRAPE MILDEW 73 



injured, but rest on the soil until the following spring, 

 when they germinate, producing two or three conidiophores 

 similar to those growing on the leaf during summer. The 

 zoospores, from the conidia of these germinating resting- 

 spores or oospores, being carried by the wind, etc., on to the 

 young vine-leaves, germinate, enter the tissues, and in turn 

 produce the mildew or summer form of the fungus. 



Preventive Means. — In Britain, where vines are grown 

 in houses, and comparatively few in number in any one 

 establishment, but little difficulty should be experienced in 

 completely arresting any outbreak of mildew. If the disease 

 appears, spray with dilute Bordeaux mixture as a check to 

 the spread of the disease, for it must be borne in mind that 

 when the mycelium has once entered the tissue of a leaf 

 it cannot be destroyed without also destroying the leaf — the 

 wisest thing to do, — but spraying will prevent the germina- 

 tion of spores on leaves that are yet healthy. In such 

 cases the vines should also be sprayed soon after the fruit 

 is set, and, if necessary, continued at intervals of a fortnight 

 until the fruit begins to ripen. Diseased leaves should be 

 removed, as they soon die, and are but of little service to 

 the vine, whereas, if allowed to remain, they probably 

 assist in spreading the disease. All fallen leaves should be 

 carefully collected and burned, otherwise the presence of 

 resting-spores in their tissues will in all probability infect 

 the vine the following season. 



In all instances where the disease has previously existed, 

 it would be wise to thoroughly drench the vines, during 

 winter before the leaf-buds move, with a solution of sulphate 

 of iron. 



M. Louis Sipiere, writing in the Acad, des ScL, 1895, 

 states that lysol, a preparation of carbolic acid, is very 



