1902.] DISEASES AND INSECTS, ETC. 1 3/ 



It has been found that by the appHcation of certain poisons 

 the spores may either be killed or their germination prevented. 

 One of the cheapest and most effective of these fungicides is 

 the well-known Bordeaux mixture. It should not be regarded 

 as a cure for, but as a preventive of fungous diseases. Treat- 

 ment with the Bordeaux mixture rests upon the philosophy 

 that where this fungicide is present on the surface of foliage, 

 or stem or fruit, fungous spores which alight there, are pre- 

 vented from further development. After the fungus has 

 gained entrance to the inner tissues its progress cannot be 

 arrested by applications of Bordeaux mixture to the surface. 

 In fact, anything of a nature sufficiently corrosive or toxic 

 to destroy the deep-seated portions of the fungus would like- 

 wise destroy the host. The investigators at experiment sta- 

 tions may publish detailed insj;ructions as to when and how the 

 fungicides should be applied. Such instructions set forth 

 general lines of treatment which should be adapted to meet 

 the conditions which vary with different seasons. From what 

 has been said concerning the habits of growth and reproduc- 

 tion of fungi, and the philosophy upon which the treatment of 

 fungicides is based, it is evident that some knowledge of the 

 life history of the particular fungus which is to be combated, 

 the period when it becomes active, its habits of spore-bearing, 

 the kind of environment which most favors its rapid develop- 

 ment, and also that which is unfavorable to its progress, is 

 necessary to intelligent, economical, and efficient treatment of 

 the disease. 



The limits of this paper will not permit particular features 

 to be considered in detail. It will serve our present purpose 

 if the plant diseases may be classed according to the accef)ted 

 methods of treating them. Let those which may be best con- 

 trolled by using the Bordeaux mixture or some similar fungi- 

 cide be considered first. Among the diseases in this class 

 which prey upon either the fruit or the foliage of the apple, or 

 both, are the bitter rot (Gloeosporium fructigenum, Berk.), 

 the fly speck (Leptothyrium pomi, Mont, and Fr., Sacc), the 

 leaf spot (Phyllosticta sp.), the scab (Venturia inequalis, 

 Cke., Aderh.), and the sooty blotch (Phyllachora pomigena, 

 Schw., Sacc). 



Among pear diseases, the leaf blight (Entomosporium ma- 

 culatum. Lev.), the leaf spot (Septoria piricola, Desm.), and 

 the scab (Venturia pirina, Aderh.). 



