34 

 MODES OF PREVENTION. 



Knowing that the Berberis is the host of the fungus, it seems 

 obvious enough that it is most desirable to banish all its species 

 from gardens, woods, and shrubberies. But this must be done 

 with one accord, and even then there may not be perfect immu- 

 nity from mildew, as the spores may be wafted from other 

 countries, where men refuse to sacrifice ornamental shrubs with- 

 out sufficient proof of their baneful influences, as they may 

 hold. The potato disease was brought by the wind to this 

 country in 1845, according to the statements of many observers. 

 It has been shown how far the spores of the Puccinia graminis 

 are carried in India, and those of the Hemileia vastatrix in Ceylon, 

 and if moths can be conveyed in the air from foreign countries, 

 the tiny spores of fungi may be thus brought from immense 

 distances. The legislators of the State of Massachusetts evidently 

 saw that it was useless for individuals to destroy the Berberis in 

 their State, at their will and pleasure, and, therefore, by their 

 famous barberry law, cited above, made its destruction com- 

 pulsory. 



Burning the straw of infected corn plants has been recom- 

 mended by experts in this country, who affirm that even if the 

 straw were heated in mixens, the spores would preserve their 

 vitality. But burning straw would be an expensive process. In 

 a season like the last, it would hardly be an exaggeration to say 

 that a fourth of the straw produced was infected more or less \vith 

 mildew. The stubble also on infected fields sown with clover, or 

 seeds, may be a dangerous source of infection, as well as the 

 stems of the numerous grasses which this fungus attacks. 



Burning in/ected straw is strongly recommended in Austral- 

 asia, America and Canada. At the Conferences of Australasian 

 delegates before alluded to, it was resolved that as the locus ot 

 the spores of the rust fungus is chiefly the straw of the infected 

 crop, it is advised that, where practicable, all infected straw, tail- 

 ings, or stubble, and all grasses immediately adjoining thereto be 

 carefully burned ; and that where infected straw must necessarily 

 be used as food or litter for stock, all the manure thereof be 

 well rotted and applied to land about to carry a non-cereal crop. 

 Straw, as a rule, in Australasia is practically a waste product, and 

 no loss is incurred in burning it, but in Great Britain it would be 

 impracticable to endeavour to stamp out infection in this way. 



PREVENTIVE SPRAYING. 



Corn plants upon land subject to mildew, whose composition 

 and constituents are of the character described above by Sir 

 John Lawes, as containing large quantities of organic matter, 

 might be advantageously sprayed with compositions of sulphate 

 of copper and lime, or sulphate of iron, and other compounds 

 similar to those employed in treating vines, potato, and other 

 plants for fungoid attacks. These should be applied as a pre- 

 ventive treatment, in the spring, before the wheat plants are 



