PODOSPHAERA 35 



typicis. In ramulis vivls Cratacgi sanguincae Pall, in sylvis pr. 

 Minussinsk. 



A 



P, oxyacanthac is known in America as the '' Cherry Powdery 

 Mildew"; also as the ** Apple Powdery Mildew," although it is 

 possible that under the latter name P, laicotriclia is sometimes in- 

 tended. 



Pammcl (266 and 267) describing the " Cherry Powdery Mil- 

 dew " states that the disease can be treated successfully with Bor- 

 deaux mixture and ammoniacal carbonate of copper. 



Galloway " (136) speaking of an '* Apple Powdery Mildew/' 

 which was identified as the present species, states that it causes the 

 most serious injury to fruit trees, especially to the young stock of 

 nurseries. In one case, owing to tlie presence of the mildew, of 

 some stocks budded, only about two thirds of the buds took. 

 Full details are here given of the preparation and application of 

 the ammoniacal carbonate of copper, which was found perfectly 

 successful as a fungicide. The interesting statement is made that 

 ^' P. oxyacanthac probably winters in a mycelial stage." 



Benson (24) attributes a disease on apple trees, widely spread 

 over the colony of New South Wales, to ''P. Kunzci Lev.," and 

 recommends the diseased trees, when in bud, to be sprayed with 

 Bordeaux mixture, follow^ed with a dressing of ammonio-carbonate 

 of copper. As the fungus was, apparently, observed only in the 

 conidial stage, the identification with the present species remains 

 doubtful. 



Waite (382) states of the present species that ''young cherry 

 trees are the chief sufferers from its attacks, but it also does con- 

 siderable harm to the peach and to young apple trees in the nur- 

 sery, and occasionally seriously injures the quince," It is also 

 noted that the most destructive form of the fungus usually bears 

 but a few perithecia, and often fails to produce any before frost puts 

 an end to the season's growth. Spraying with a mixture of half an 

 ounce of potassium sulphide in a gallon of water is recommended. 



P. oxyacanthac sometimes attacks Crataegus Oxyacantha so 

 severely that it kills the plant. Eriksson (119) records such cases 

 from the neighborhood of Stockholm, where young trees up to 4 

 feet high were destroyed. It is also stated that the fungus fre- 

 quently produces no perithecia on this host. 



