156 INSECTICIDES, FFNGICIDES, AND WEED KILLERS. 



is in the spring, preferably at the time the young buds begin to gi'ow ; 

 it is done under cover by dusting the fields as regularly as possible. 

 Working thus the plaster has the further advantage of guaranteeing 

 the young plants so covered against the rigours of late frost. Plaster 

 xised in arboriculture is regarded as an injurious manure causing the 

 fruit to I'ot. 



Use against Late Frosts. — The adhesion of plaster and its siccative 

 power pei'mit its use against the late frosts of spring. The " powder- 

 ing " used for some years in France and very much in vogue in Italy 

 may entirely preserve the vine against late frosts so dreaded in viti- 

 culture. By means of a sulphurator the plaster is spread as an im- 

 })alpable powder on the vines at the time frosts are feared. In Italy 

 plastering is associated with the treatment for the mildew of the vine 

 oidium, using a mixture containing ^ of sulphide and § of plaster 

 (wood ashes and lime are also used for the same purpose in Italy). 

 Ouvray advises to utilize this same process against frost to preserve 

 flowers, or the very delicate young fruit of fruit trees ; powdering is, 

 therefore, done say a little before flowering or immediately afterwards. 

 Powdering forms an economic and efficient protection against frost 

 and may find numerous applications in the culture of marshy land. 



Use against Fungi. — Sorauer advises abundant manuring with 

 plaster to pi-event the rotting of roots due to the development of the 

 most diverse fungi, such as Armillaria mellea, Quellet, Flbrillaria 

 xylotlirica, Linh., Bliizoct'uiia violacea, Tul. ; this manuring has some- 

 times given good results. 



Botrytis cinerea,''- Pers. (grey rot of the vine). — Sorauer advises the 

 use of plaster in the same condition as slaked lime in fine powder. 

 As soon as this dreaded disease appears, plaster is sprayed on the 

 fruits ; the fruits are thus protected, for the fine layer of plaster which 

 covers them prevents the fungi from finding on the surface of the 

 gi-ape a propitious soil for their development. Eecommended tor the 

 first time by De la Bathie, experiments made in the South of France 

 have not given the good results described. 



Use against Insects. — Plaster having no caustic action can only 

 act as an asphyxiant. Owing to its extreme fineness, it is introduced 

 through the stagmata into the respii'atory organs of insects, where 

 under the influence of moisture it hydrates, swells, and causes death. 

 Without being mortal to certain larvae, it annoys them very much and 

 keeps tliem away from plants. Plaster is used with much greater 

 success against aUlses. Haltica amjoelophagufi, Guer. (altise of the vine). 

 — So that the eftect may be perfect, it is necessary to powder the vine 

 so that the plaster is projected on to the lower part of the leaves, for 

 it is there that the larvae and insects are. Brocchi greatly advises its 

 use. But it is not the altise of the vine alone which may be com- 

 bated in this way, the most diverse altises succumb or are driven 

 away owing to its use. 



Haltica ncbiilosa, L. (Cassida nebulosa). — Doering advises the use of 

 plaster against this larvae as well as for the caterpillar of Noctua gamma. 



1 The conidia of Sclerotina Fuckeliana, De Bary. — Tk. 



