EXPKKIMKNT STATION l.'Kl'OUT. 525 



Po\(rdery Mildew^s of the Vegetable Garden. 



Tho cueuml)t'r is sometimes troubled with a ijowtlerv mildew 

 {Erysiphe Cichoracearum DC), and the same speeies is occasionally 

 met w'ith upon the pumpkin. Garden peas, particuhirly tlie late 

 sorts, are badly infested with Erijsiphe Polygoni DC"., a mildew of 

 wide distribution and growing upon nearly sixty kinds of plants. 

 Experiments show that it can be controlled by fungicides. The beans 

 of various sorts usually escape from the attacks of this mildew. 



Pofrdery Mildews of the Greenhouse. 



The le'ading })owdery mildew that mako;- trouljle for the grower of 

 plants under glass is the Sphcerotheca pannosa Wallr., which quickly 

 produces white patches upon the rose leaves. It is distributed through- 

 out the world and upon many sjx^cies of roses, the ]5?ach Ijeing the 

 only other host plant, outside of tlie rose genus, thus far known to be 

 infested Ijy this mildew. 



There is another species of mildew upon roses, namely, Sphwrotheca 

 humiili (DC), and therefore there is much confusion between 

 these two last-named kinds, Ijecause the determinations are carelessly 

 made, without a study of the perithecia, which are often omitted in 

 the development of the mildew. 



The second sj^ecies of mildew pestering the greenhouse plants is 

 Erijsiphe Cichoracearum DC, which thrives upon the cucumber and 

 other plants of its family, and asters, dahlias, zinnias of the composite 

 family, probably including the chrysanthemums. The last in an in- 

 teresting case of the rank and destructive growth of tlie conidial, or 

 i^ummer form of the mildew, while the "winter fruit" is omitte<1. 

 Until tlie latter perithecia can Ik? found, the old name of Oidium 

 Cltri/saiitJicmum Eabenh. will lie retained to designate this pest. In 

 a similar way, Oidium leucoconium Desm. was the name for the rose 

 mildew until its final determination was made. 



The jnildew of the cucumber and tlu' chrysanthomum (?) is very 

 destructive to indoor phlox, and something of this host and its pest 

 will be said under the head of "Remedies."' 



