280 



Minnesota Plant Diseases. 



Rust of pyrola \Chrysomyxa pirolae (DC.} Rostr.]. The 

 cluster cup stage probably occurs on some conifer. See Dis- 

 eases of Wild Plants. 



Rust of milkweeds 

 \Cronartium asclepia- 

 deum (Willd.) Fr.]. 

 Sometimes found on 

 oak leaves. See Dis- 

 eases of Wild Flowers. 

 The cluster-cups are 

 probably produced on 

 pine leaves. See Leaf 

 Rust of Pines. Dis- 

 eases of Timber and 

 Shade Trees. 



The mistletoe dis- 

 ease of spruce [Ra- 

 zoumofskya pus ill a 

 (Peck) Kuntze]. This 

 parasite is a flowering 

 plant of the mistletoe 

 family, and is the only 

 plant of this family 

 which is native to o in- 

 state. It produces a 

 very serious disease of 

 the spruce and both 

 white and black spruce 

 are a ff e c t e d. The 

 presence of the para- 

 site in the tree can 

 usually be discovered 

 from a distance by the 

 presence of large 

 "w i t c h e s'-brooms." 

 The part of the spruce 

 which is attacked mul- 



tiplies itS branches and 



SO 



p IG . 13S. Willow leaf rust (Melampsora salicina). A 

 willow leaf almost covered with the crust-like clus- 

 ters of winter spcres. Original. 



