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tinually unfolding and new rust pustules are continually breaking 

 forth, so that unless one were to dust his plants every day, new 

 infections are found to develop if there is sufficient moisture to 

 induce the spores to germinate. 



Some years ago the writer's attention was directed to a case of 

 heavy infection of seedling hollyhocks that had been grown in flats 

 in a cold-frame. The seedlings were about five or six inches high 

 and heavily rusted. They were taken from the cold-frames and 

 thoroughly dusted with Pomo-green, and, after they had been 

 planted in the borders, the dust was applied two or three times 

 a week until the plants had reached some size, with very satisfac- 

 tory results. Just how the seedlings originally became infected 

 is not clear. Probably rust pustules were carried over on fragments 

 of the fruit scales or on pieces of leaves, and the infection spread 

 to the young leaves in the moist cold-frames. The plants in our 

 perennial borders were kept free from the rust for the two suc- 

 ceeding years with very little attention given them beyond a few 

 applications of dust in the spring and the careful destruction of 

 old plant parts. Last year, however, perhaps owing to the intro- 

 duction of several new varieties, the rust appeared in epidemic 

 form in plants about two feet high. In spite of repeated applica- 

 tions of sulphur dust, the rust persisted until the end of the sea- 

 son. A thorough clean-up of the old infected plants and a care- 

 ful dusting this spring as the leaves appeared served to give us 

 rust-free plants. There were only two plants out of a large num- 

 ber that showed any rust. These evidently had escaped notice 

 until they were about a foot high, when it was found that practically 

 every leaf was spotted with the rust. Infected leaves were removed 

 and the plants were thoroughly dusted about twice a week. This 

 did not prevent the rust from developing considerably on new 

 leaves as they unfolded. It is clear from this that successful con- 

 trol measures must involve the prevention of the earliest infec- 

 tions. The removal of infected leaves is not sufficient, as rust 

 pustules often develop on stems and a single pustule alone serves 

 as a great source of trouble. 



To control hollyhock rust: A. Destroy all plant parts after 

 blossom time so that no infected material can come in contact with 

 the new leaves developed m late summer and fall. B. Dust the 

 young leaves the following spring with a good grade of dusting 



