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BETTER FRUIT 



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Tomato Blight a Serious Menace to Tomato Industry 



By F. D. Heald, Professor of Plant Pathology, Washington State College, and Plant Pathologist of the Washington Agricultural Experiment Station 



DURING Ihc past 20 years tomato 

 blight, known also as the "yel- 

 lows," "yellow blight" or "western 

 blight," has been a serious menace to 

 the tomato-growing industry in many 

 parts of the Pacific Coast country. Up 

 to the present time the trouble has been 

 supposed to be jjcculiar to the Pacific 

 Northwest. Various investigators have 

 given more or less attention to the 

 study of the disease since 18f)C, but the 

 first publication claiming the establish- 

 ment of the cause of the trouble ap- 

 peared in 1014. In the bulletin referred 

 lo H. B. Humi)hre.\-, in "Studies on the 

 Relation of (Certain Species of Fu- 

 sarium to the Tomato Blight of the 

 Pacific Northwest," claims that tomato 

 blight is caused by one or more species 



rivmg more 

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of Fusariuni which parasitize the root 

 system. His results were basetl upon 

 observations covering a number of 

 years, but notwithstanding this fact 

 there seemed to be some ground for 

 questioning the reliability of his con- 

 clusions. 



A strong element of doubt was intro- 

 duced for two reasons: (1) The tomato 

 blight is lessened in sevei'ity by cer- 

 tain factois which ordinarily are favor- 

 able to Fusaiium diseases, notably, in- 

 creased use of fertilizer. (2) The symp- 

 toms of the disease, as recorded by 

 Hum])hrey and others, are . different 

 from what one would expect if the 

 causal organism were a Fusarium. On 

 account of this doubt as to the true 

 cause of the disease the investigations 

 carried out during the past season were 

 directed in the main to discovering 

 this one fundamental fact, the cause 

 of the disease. It should be constantly 

 borne in mind that the important point 

 in all control work is clear and ilelinite 

 information concerning the cause of a 



Tomato Roots showing Solerotia of Rlii/ocfonia 



trouble. It seems that much of the aim- 

 less wandering in control work of the 

 past twenty years as far as tomato 

 blight is concerned might have been 

 avoided if we could have had a defi- 

 nite understanding of the ctmse of the 

 trouble. 



The investigations carried out at the 

 Experiment Station during the past 

 season, as well as the field observations 

 made at various places in the state and 

 adjacent territory, have all i)ointed to 

 the fact that tomato blight is caused 

 b>' the sterile fungus, Rhizoctonia, ami 

 that the species of Fusarium reported 

 by Ilumphiey are entirely secondarx 

 in their relation to the disease. II 

 seems strange that with all the work of 

 able investigators during the past 

 twenty \eai-s, the ctuise of tomato 

 blight should have remained a mystery 

 up to the ijrescnl time. This is no 

 reflection upon the ability of the work- 

 ers connected with Ibis problem, but 

 rather points to the ditliciilties that the 

 scientist encoimlers when delving into 

 the realm of the imknown. 



In the light of the investigations con- 

 ducletl (luring the past season it will 

 be necessary lo revise somewhat the 



description of the symptomatology 

 characteristic of the disease. The great 

 variation in the symptoms accompany- 

 ing the attack should lead us to dis- 

 card the old names, such as blight, yel- 

 lows and yellow blight, while western 

 blight is equally objectionable, since 

 the disease is not peculiar to this 

 region. The least confusion will pre- 

 vail if we designate the disease b\- the 



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WHEN WRITING ADVERTISERS MENTION BETTER FRCIT 



WHEN WRITING ADVERTISERS MENTION BETTER FRUIT 



