258 



Rust 



Caused by Uromyccs caryophyllinus (Schw.) W'int. 



This rust appears as small, reddish-brown, more or less circular 

 spots upon the leaves and stems, the plant tissue for some distance around 

 usually taking on a sickly, yellowish color. 



This disease is a pest in greenhouses especially, where it may be 

 quite destructive. It is known in 10 counties in Illinois, as shown on 

 Map 123, indicating its wide-spread occurrence over practically the whole 

 state. 



Control measures consist, first of all, in the selection of cuttings 

 which are not infected. Free ventilation, and watering of the soil only, 

 with a periodical spraying with copper sulfate, one pound to 25 gallons 

 of water, are very helpful in preventing the spread of the disease in 

 greenhouses. 



Virginia Creeper 



The Virginia creeper, commonly used as a' decorative vine, is subject 

 to two diseases, which are of some importance in that they may impair 

 the appearance of the vine and may reduce the growth of the plant in the 

 ntirsery. 



Leaf spot 

 Caused by Gnignardia bidzvcllii (Ell.) V. & R. 



The leaf spot is identical with the black-rot disease of grapes and 

 has, on the leaves, essentially the same appearance. 



It is known lo occur in 21 counties, as shown on Map 124. It ap- 

 pears to be especially abundant in southern Illinois, with only occasiona 

 occurrence northward. 



Powdery mildew 

 Caused by Uncuuila nccator (Schw.) Burr. 



Powdery mildew is identical in appearance with the powdery mildew 

 of grapes. 



It is known to occur in !> counties as shown on Map 125. It is ap- 

 parently widely distributed in Illinois, with a most frequent occurrence 

 in the northern part of the state. 



This and the preceding disease of the X'irginia creeper are controlled 

 by the same means as on grapes. 



Snapdragon 



The snapdragon, grown extensively in greenhouses for cut flowers 

 and in gardens for decoration, is subject in Illinois to one common dis- 

 ease, the snapdragon rust. 



