Greenhouse, Hollyhock. 311 



is injurious to the plants grown, an occasional wetting and the 

 removal of infested leaves will be sufficient to subdue them. 



Insecticides which kill by contact may also be used success- 

 fully, but they are not generally necessary. The fumes of 

 sulphur, produced as described on page 175, are also said to 

 have a beneficial action in the destruction of the red spider, 

 as well as of the mite. 



Snail; Slug. Description. The foliage of plants grown in 

 moist situations under glass is frequently riddled or entirely 

 devoured by snails. In dryer places so much harm is not done. 

 These animals feed mostly in the night, concealing themselves 

 under boards or other objects, or in crevices which are dark. 

 They feed upon tender vegetation of nearly all kinds, and may 

 cause irreparable damage to young seedlings or cuttings in a 

 single night. 



Treatment. Large numbers of snails may be caught by ex- 

 amining the houses with a light after dark. They may also be 

 trapped by placing pieces of turnip, cabbage, or other vegetable 

 matter about the houses in such a manner that hiding-places 

 may be formed. The creatures congregate under the bait, and 

 often large numbers are caught in this manner. Salt, and also 

 lime, are said to be distasteful to them. 



HOLLYHOCK. 

 FUNGOUS DISEASES. 



Rust (Puccinia Malvacearum, Mont.). Description. During 

 May and June the stems and leaves of the hollyhock may 

 become discolored by small spots which at first are yellow, but 

 later they become brown. These diseased parts are due to the 

 presence of the rust fungus, a parasite which may develop so 

 vigorously and abundantly that the leaves of the host-plant 

 become dry and dead, as if scorched. The plants may be 

 entirely prevented from blossoming, and unless measures are 

 taken to check the disease, hollyhocks may be forced from cul- 

 tivation, as has occurred in some parts of Europe. 



Treatment. Hollyhock rust may be practically prevented by 

 spraying the foliage with some good fungicide as soon as the 

 leaves appear in the spring. The applications should be re- 

 peated frequently enough to keep the young growths covered. 



