10 July, 1917.] Anthracnose or Black Spot of the Vine. 417 



tlie h:i)"i1 •■tl'cits noted in the case of two successive treatments, but, wlien :i sulli- 

 ciently tliiek layer of outer cells has been destroyed, an obstacle to the formation 

 of fresh fructiiications is established. This is what occurred in the case of 

 sulphuric acid. Hence the value of the usual classic acid iron sulphate treat- 

 ment (1 per cent. acid). Nevertheless, in iledoe, according to Hover de la 

 Girodiiy |K. Vit., Vol. V., p. 515), 10 |jer cent, sulphuric acid hn> been even 

 better. Bouchard, the proposer of tliis treatment, has found it entirely 

 .satisfactory. 



If it be desiied to use iron sulphate, it would be well to add to it a fair 

 proportion of sulphuric acid. 



Viala and Pacottet hold similar opinions, though they are not quite 

 so reassuring — 



ViticiUtnrist-- know how difficult it is to cunibat Anthracnose by preventive 

 treatments with acid iron sulphate. They know also that the action of the swal> 

 is only really efficacious if applied shortly before the buds sprout. 



In order to reach tlie internal sclemtia, inqiregnation, or dill'usion, of the 

 corrosive li<iiiid throuj;li the tissues is necessary; this can, however, only act on 

 the conidiophores at the moment of their formation, or else on the spores which 

 they have produced. Kven though the acid iron sulphate reach the sclerotia, it 

 can only corrode tlie first layers of parencliymatous cells, without penetrating to 

 the interior, unless it were to burn and destroy the tissues of the canes. It is 

 thus easier to understand the efficacy of double treatment with acid iron sulphate, 

 with a fortnight's interval between each application. Even then it is conceivable 

 that their efficacy is not absolute. 



Sclerotia are not only formed on the surface of scars, they are also found in 

 deep cavities and fissures where they may be beyond l;he reach of the swab ; 

 they are, of course, altogether so in internal cavities (Fi«. 1.3. Condia 

 forined therein are, however, powerless to infect young growth in spring. The 

 most dangerous sclerotia are those in deep narrow fissures, where the swab can 

 scarcely penetrate {Figs. 14 and 15). 



It may be here explained that Fig. 9 and Figs. 13 to 16 are leproduetions of 

 drawings made direct from the microscope ; though thej' are exact representations 

 of what is actually seen, they probably convey less to those unaccustomed to 

 microscope work than diagrams such as Figs. 6 to 8 and 10 to 12, which are 

 conventional, and dravs'n to illustrate certain points only. 



From these extracts the need for very thorough treatment will be 

 readily understood. In addition to sclerotia, kystes must be briefly 

 leferred to. These small bodies, which seem to be another resting forn., 

 develop at the surface of the exposed sclerotia on the scars. (See 

 Fig. 16.) They are no doubt washed by rain ou to the main stem of 

 the Tine, where they remain until the following spring, and germinate 

 on the return of favorable weather conditions. These, as well as some 

 other resting stages, render necessary the treatment of the old wood ol 

 the vine; if sclerotia were the only wintering form, it would only be 

 necessary to treat the young wood on which tha scars are situated. 



Treatment. 



It is evident that the artificial destruction of all hibernating forms 

 would remove the cause of infection, and prevent a fresh outbreak the 

 following spring, hence tlie efficiency of the winter swab, which was 

 practically demonstrated long before the life history of the fungus was 

 thoroughly investigated. Foex (Coiirs Complef, de Viticulture — 1886 

 edition) — mentions swabbing with concentrated iron sulphate solution, 

 a treatment! invented by M. Schnorf. He further states that, accord- 

 ing to M. F. Skawinski, better results are obtained by using newly 

 manufactured iron sulphate, which 'contains 1 per cent, of free sulphuric 

 acid. Thus was evolved the acid iron sulphate swab, which is still the 

 standard preventive treatment. As has been shown above, Boyer de 



7233.-2 



