158 



Illinois Natural History Survey Bulletin 



Vol. 27. Art. 2 



Foliage diseases which cause especial 

 damage during cool, moist springs affect 

 many species of trees. The most destruc- 

 tive foliage diseases are anthracnose of 

 ash, maple, oak, and sycamore; blotch of 

 buckeve and horsechestnut ; and leaf spot 

 of elm. hawthorn, maple, oak, and walnut. 



Some trees decline and die each year 

 because of unfavorable growing condi- 

 tions that include physiological disorders. 

 adverse weather conditions, and mechani- 

 cal injuries. These conditions, as well as 

 disease organisms, have received the at- 

 tention of Natural History Survey plant 

 pathologists. 



Research on the control of foliage dis- 

 eases includes testing of numerous fungi- 

 cides each year. In some years as manv 

 as 18 species of trees have been treated 

 with fungicides and as many as 12 differ- 

 ent fungicides have been tested on one or 

 more species. An example of an effecti\e 

 control measure resulting from these tests 

 is the use of organic mercury fungicides 

 to control anthracnose of sycamore. 



Chemotherapy. — One phase of Nat- 

 ural History Survey research on the con- 

 trol of tree diseases relates to the effec- 

 tiveness of various chemicals in prevent- 

 ing fungi from infecting trees or from 

 causing disease symptoms after they have 

 infected the trees. The early studies were 

 confined mainly to oak wilt; the present 

 studies include diseases of several species 

 of trees and especially oak wilt, Dutch 

 elm disease, and Verticillium wilt of elm. 

 maple, and other trees. Of the hundreds 

 of chemical compounds tested, a few 

 systemic fungicides and antibiotic ma- 

 terials appear to be effective in preventing 

 disease development. To obtain more in- 

 formation on what happens when these 

 materials are introduced into trees, plant 

 pathologists are studying the physiology 

 of trees as well as the physiology of the 

 fungi. The staff members who have car- 

 ried on this program are Paul F. Hoff- 

 man, Eugene B. Himelick, Irving R. 

 Schneider, John M. Ferris, and Walter 

 Hartstirn. 



Floricultural Pathology 



Little research by the Natural History 

 Survey was done in floricultural pathol- 

 og>' before 1939. In response to numerous 

 requests for help in dealing with disease 



problems in floricultural crops, a pro- 

 gram of research was initiated, and Don 

 B. Creager was appointed to the staff in 

 September of 1939. This program, car- 

 ried on by Creager for 5 years and con- 

 tinued b\ J. L. Forsberg. included work 

 on diseases of greenhouse crops and field- 

 and garden-grown floricultural plants. 

 Much attention was given to bulbous 

 ornamental plants, which were being 

 propagated extensively in Illinois for 

 shipment to other states. 



The early work was concerned with 

 ( 1 ) obtaining as much information as 

 possible about diseases important to Illi- 

 nois growers. (2) conducting research on 

 diseases for which vital information on 

 cause and control was lacking, and (3) 

 rendering every possible aid to growers 

 in the recognition and control of diseases 

 in their crops. As the work progressed 

 more attention was given to developing 

 disease control measures that would be 

 more effective than those that were being 

 used. 



Crops which have received attention 

 during the course of this work are ama- 

 rylHs, aster, azalea, begonia, calla, carna- 

 tion, chrysanthemum, gardenia, geranium, 

 gerbera, gladiolus, hollyhock, hydrangea, 

 iris, ivy, lily, orchid, peony, peperomia, 

 periwinkle, petunia, poinsettia, rose, Afri- 

 can violet, snapdragon, stevia, stock, 

 sweet pea, tuberose, tulip, violet, and 

 zinnia. Of these crops, gladiolus, rose, 

 and carnation are grown in greatest 

 quantity, and. since all three crops are 

 subject to a number of destructive dis- 

 eases, more work has been done on them 

 than on the other crops. 



Because of the serious losses due to 

 diseases of gladiolus in the large com- 

 mercial gladiolus growing area in Kan- 

 kakee County, much research work has 

 been directed toward developing effective 

 control measures for these diseases. Prior 

 to 1940, gladiolus corms generally were 

 not treated for disease control, but in re- 

 cent years nearly all commercial gladiolus 

 planting stocks in all parts of the United 

 States have been treated with a fungicide 

 before being planted. This practice has 

 developed largely as a result of the suc- 

 cess of experimental treatments by Illi- 

 nois Natural History Survey pathologists. 

 If these or other equally effective treat- 



