WASTES IN RELATION TO AGRICULTURE AND FORESTRY 



75 



disease. Thus, countless kinds were made in the 

 past and more are continually being made (106). 

 Control of the disease has been possible through 

 a continuous program of breeding work to develop 

 resistant varieties of wheat, oats, and barley. 



Red stele disease of strawberry is an example of 

 a plant disease fungus that can live for many years 

 in soil even if strawberries are not present. The 

 fungus spreads through the soil by microscopic 

 swimming cells known as zoospores. Flood and 

 drainage water can carry the spores long distances 

 and thus infect other areas. The disease can be 

 spread by moving soil on machinery or planting 

 stock, and such. Several strains of Phytophthora 

 fragariae, the fungus causing red stele, exist. The 

 disease is controlled by breeding resistant varieties 

 of strawberry plants (61). 



The Texas agricultural experiment station was 

 established in 1888, and work started the first week 

 in March, with "not much being done, however, 

 until the last week in the month." After deliberate 

 consideration it was thought best to take up, first, 

 a study of a practicable and economical method of 

 cattle feeding, and second, "a study of the disease 

 of the cotton plant known as 'Cotton Blight' or 

 'Root Rot" " (48). Bulletin No. 4 of the station 

 dated December 1888, is "Root Rot of Cotton, or 

 'Cotton Blight'" (91). The general character- 

 istics, the infectious nature, and the treatment of 

 the disease were discussed. The statement was 

 made "It will be somewhat difficult to treat this 

 disease." Experience over the past 80 years in the 

 Blacklands area of Texas has proved that this 

 comment was an understatement. 



Now we know that more than 2,000 species of 

 wild and cultivated plants are attacked by the soil 

 inhabiting fungus Phymatotrichum omnivorwn, 

 which causes cotton root rot. The disease has been 

 one of the more difficult to control. The search for 

 cotton varieties resistant to the disease has yielded 

 negative results. The greatest promise of practical 

 control of root rot appears to lie in the use of 

 organic manure, particularly in the form of 

 legumes. The use of organic manures, plus rota- 

 tion, early fall plowing, and early maturing 

 varieties, should provide satisfactory control of 

 root rot (14). 



Cabbage yellows is a disease caused by a fungus, 

 Fusarlum oxysporum f. conglutinans. The fungus 

 can exist indefinitely in soil. It may be dissemi- 



nated in soil moved by wind, water, animals, and 

 man. It is most destructive throughout the Corn 

 Belt and as far north as central Wisconsin. 

 Yellows was so destructive in 1910 that research 

 was undertaken at the Wisconsin agricultural ex- 

 periment station on the disease. All attempts at 

 practical control were unsuccessful but, by selec- 

 tion, a resistant variety, Wisconsin Hollander, was 

 obtained and released in 1916. Through selection 

 and hybridization, yellows resistant varieties to 

 suit most seasons and market requirements have 

 been obtained. The work of breeding new varieties 

 to meet changing requirements continues (130). 



White stringy root rot of conifers is a disease 

 caused by the fungus Fomes annosus Fr. and is 

 present throughout softwood forests nationwide. 

 It had been observed rotting white pine roots in 

 the early part of the century but was of small con- 

 cern. The disease has been a source of considerable 

 loss in continental Europe where planting has 

 been an important method of reforestation for 

 generations. Scientists of the U.S. Department of 

 Agriculture reported in 1944, as a result of study- 

 ing white pine plantings at Biltmore, X.C., that 

 75 percent of previously thinned plots had root 

 and butt rots. The rots were caused mostly by 

 F. annosus. 



The disease frequently becomes established 

 when a healthy conifer stand is thinned. Airborne 

 spores of the fungus inoculate freshly cut stumps. 

 The spores germinate and the fungus grows into 

 the stump roots. Roots of healthy trees in contact 

 with infected stump roots become infected. Also, 

 sporophores are produced on the stump, thus a 

 foci for dissemination of airborne spores is estab- 

 lished. Once tree roots are infected, the fungus 

 may survive below ground for 50 years or more 

 (12). 



Based on British experience, creosote has been 

 recommended for control of F. annosus. However, 

 cooperative research of the U.S. Department of 

 Agriculture with the Missouri agricultural experi- 

 ment station suggests other materials such as urea, 

 sodium tetraborate decaliydrate. and borax are 

 superior to creosote for control (IS). The stumps 

 must be treated after each thinning. 



Allergens 



Any weed-control practice performed K 

 flowering will prevent pollen formation. Then 

 no research underway that is designed specifically 



