108 REPORT OF THE COMMISSIONER OF AGRICULTURE. 



loaves as to give tliem the appearance of having been spattered and 

 blotched with whitewash, the sjoots being a imre dead white. Tliis 

 mildew is also found on the lower surface of the leaves, but never to 

 the same extent as upon the upj)er side; and as it is only in the latter 

 part of the season that it has been observed there at all, its presence 

 is doubtless due to an extension of growth from other parts, as from 

 the petiole. 



Upon the young and tender shoots the fungus is often particularly 

 abundant, its action being to check their growth. Its presence on 

 the older and half-ripened shoots is indicated by distinct but irregu- 

 lar brownish blotches in the epidermis. Sometimes the Unciniila 

 apj)ears during the season of bloom, and, coming on the newly ex- 

 panded flowers, causes them to abort. Attacking very young berries 

 when these are no larger than shot or small peas, their growth is 

 permanently checked. Cases have come under my observation where 

 the Peronosporu, the Uncinula, and the fungus of the Black-Rot were 

 all engaged in their work of destruction upon a single bunch of 

 grapes. It is needless to say that the destruction was complete. 



Upon the older berries the presence of the Powdery Mildew is made 

 evident before the mycelial threads have obtained sufficient growth 

 to become conspicuous themselves by the minute brownish spots 

 produced by the action of the suckers on the epidermal cells. These 

 spots eventually become confluent, the epidermis dies or is so affected 

 that it will no longer expand with the growth of the berry and con- 

 sequently bursts, first forming tiny, then gaping tears, the result 

 being the death and decay of the berry. Oftentimes the fungus 

 spreads over only a small portion of the berry; this part ceases to 

 grow, and a much distorted or imperfectly formed fruit is the result. 

 The distortions are often carried so far that the berries crack open, ' 

 exposing the seeds. We sometimes find nearly full-grown berries 

 completely overgrown with the mycelium of the Uncinula, so that 

 the brown specks above mentioned, if present at all, are completely 

 hid from view. These berries eventually become dry and shriveled 

 and finally drop off. 



REMEDIES. 



The flowers of sulphur is an efficient and the usual remedy employed 

 for this form of Mildew. 



It is not necessary to bring the particles of sulphur into immediate 

 contact with the spores and fungus threads to effect their destruction; 

 the fumes which this substance emits at elevated temperatures will 

 accomplish this. The knowledge that heat favors the production of 

 these fumes makes it obvious that the best time to make the applica- 

 tion is when the thermometer stands the highest. The fumes are 

 given off rapidly when the temperature ranges between 75° and 95° F. 

 The higher the temperature the more abundant are these fumes, and 

 consequently the more rapid will be the destruction of the parasite. 

 In latitudes where the soil temperature reaches 110° to 120° during the 

 day it has been found that spreading the sulphur on the ground under 

 the vines is sufficient to accomplish the destruction of the mildew, 

 and a like result is obtained by dusting the sulphur over the hot-water 

 pipes in the grapery, providing these be sufficiently heated. 



If the sulphuring be delayed until the formation of the perithecia it 

 is not likely to do much good, for although it may destroy the myce- 

 lial threads, the ascospores are too well protected within their hard 

 coverings to be injured by the application. 



