YELLOWS, A SERIOUS DISEASE OF TOMATOES 



Hy MicuAJX Shapovai.ov, Patholot/ixt, Office of Vct/i lahh (ind Fumye Diseases, 

 liurciiH (if I 'I (I lit I ti dust I II 



CONTENTS 



Page 

 Origin of the nnmo "yellows" 2 



Ui'itstiiis for tin- nt'W iiatuo 2 



The problfin t»f control 3 



ORIGIN OF THE NAME " YELLOWS " 



"Tomato yellows"' is merely a new name for tliat old plajjiie of 

 the West wliicii lias been more or less generally known as western 

 yellow tomato blifrht. There are not many tomato growers west of 

 the Kocky Mountains who are not familiar with the appearance of 

 this disease: General yellowin«jj of the plant, ri<;id upwardly rolling 

 leaves, purple veins, and arrested growth with prematuri' death. To 

 bo exact, it is not even a strictlv new name. Plant pathologists of 

 the Idaho (1!)()4) and the Waslungton (ll)Li2 and 11)24) State Agri- 

 cultural E.\i)eriment Stations, where this disease has been studied 

 for a greater number of years than at any other institution, have 

 used the name "yellows" in their annual reports. The writer now 

 recommends that this name be used in the future generally and 

 exclusively in i)refeience to and in place of any other synonyms, 

 such as western blight, yellow blight, summer blight, or simply 

 blight. There are several reasons, both scientific and i)ractical. for 

 adopting this name. Tiie principal ones ai'C stated in the following 

 paragraphs. 



REASONS FOR THE NEW NA.ME 



A correct understanding of the nature of this disea.se has finally 

 been reached, altiiough as yet this knowledge is necessarily of a gen- 

 eral character. It is now known that the malady is a virus disease, 

 or, in other words, that its infective principle, whatever it may be, 

 lives and inultii)lics in the juices of the |)lants. It is akin to curly 

 top of sugar beets and may be carried fiom plant to plant by beet 

 leaf hoppers. It is certain that if these insects feed first on the 

 diseased l)eet and then on a healthy tomato, typical symptoms of 

 Avhat has been known as western yellow blight will result, if other 

 conditions are favorable. In like manner this trouble may be 

 transferred from other plants, both wild and cultivated, if they 

 li;i|)pen to b(> affected by the same virus. Such virus diseases, trans- 

 mitted by leaf hoppers' (distinct, however, from another large and 

 well-known group of virus diseases known as mosaic and transmitted 



78094''— 28 



