Family Compositae 149 



Rust 



Caused by Puccinia helianthi Schw. 



Rust attacks the wild as well as the cultivated sun- 

 flower, producing bUsters or sori on the leaves. The 

 former are at first yeUow or brown, but later in the 

 season become black. Badly infected leaves turn 

 yeUow, then curl and dry up. This results in a re- 

 duction in the yield of seed, which for the most part 

 fails to fin out properly. This rust seems to attack 

 the sunflower only and is apparently unable to infect 

 the Jerusalem artichoke. Clean culture and des- 

 troying the refuse by fire is advised. 



WEEDS 



The family Compositas contains a large number of 

 weeds. The following are often troublesome: rag- 

 weed {Ambrosia artemisifolia) , great ragweed {Am- 

 brosia irijida). Mayweed {Anthemis cotida), burdock 

 {Arctium minus), ox-eye daisy {Chrysanthemum 

 leucanthemum pinnatifidum), blue sailors {Cicorum 

 intybus), buU thistle {Cirsium lanceolatum), fireweed 

 {Erechtites hieracifolia) , wild or tall lettuce {lactuca 

 canadensis), prickly lettuce {Lactuca scariola), fall 

 dandelion {Leontodon autumnalis), Canada golden- 

 rod {Solidago canadensis), dandeUon {Taraxacum 

 officinale), cocklebur {Xanthium commune). 



Of the weeds which are attacked by downy mildew, 

 Plasmopara Halstedii Pari., may be mentioned the 

 ragweed, the great ragweed, and Canada goldenrod. 



